Introduction and overview:
In the USA, most individuals don't worry too much about harmful parasites, however, they do exist and parasitic infections can occur. Other parts of the world suffer from many harmful parasites and infections.
A Few Basic Definitions:
A Few Basic Definitions:
- Epidemiology: This is the study of the causes, factors, prevention, frequency and distribution of infectious diseases in a community, locally, statewide, countrywide and across the globe.
- Epidemic: an outbreak of infectious disease that causes a rise in the number of cases in the same geographic area or region
- Endemic: local outbreaks common to a particular area or region that occur regularly or continuously or during expected cycles within a particular population
- Pandemic: a global outbreak of disease
- Vector: a living carrier of disease (able to carry a pathogenic microbe from an infected host to a noninfected host)
- Carrier: a host that is carrying a parasite but is asymptomatic (not showing any clinical signs or symptoms of infection)
- Host: a human, animal or plant that has a parasite
- Definitive host: an animal host that a parasite exists on or within, which passed its entire life cycle or adulthood on or in the host
- Intermediate host: a parasite passes its larval stage or asexual reproduction phase in an animal, and then it is transported or carried to another host
- Commensalism: a relationship between 2 organisms in which one is being benefited and the other is neither being benefited nor being harmed
- Symbiosis: a relationship between 2 organisms in which both are mutually benefiting each other and interdependent upon each other; neither are harming each other
- Parasitism: a relationship between 2 organisms in which one is living on or within the other and is dependent upon the other one or even causing harm to the other one by taking its nutrients
- Pathogen: a causative agent of infectious disease
- Pathogenic: able to cause disease
- Pathogenicity: a parasite's ability to cause disease and pathological changes in or on a host
- Infection: an invasion of the host by a pathogenic organism, which elicits and immune response
- Infestation: colonization of arthropods either on or within the host (bedbugs, lice, fleas, crabs, ticks, mites, other bugs)
- Fomite: an inanimate object that harbors a pathogenic microbe (towel, comb, piece of clothing, rug/carpet, bedding, etc...)
- Virulence: severity of disease
- Zoonosis: a disease in a human that was inadvertantly caused by a parasite that typically lives in or on an animal as its usual host
- Parasitemia: the presence of parasites in the blood
Classification: (Kingdom, phylum, class, order, family, genus, species)
- Domain: Eukarya
- Kingdom: Protista; Animalia
- Phylum: Protozoa
- Class: (classified by means of locomotion, or how they move; unicellular)
- Class Lobosea: move by pseudopodia
- Class Zoomastigophorea: move by flagella
- Amoeba (move via pseudopods, or "false feet")
- Entamoeba histolytica
- Entamoeba hartmannii
- Entamoeba coli
- Amoeba proteus
- Endolimax nana
- Iodamoeba butschlii
- Amoeboflagellate
- Acanthamoeba
- Naegleria fowleri
- Flagellates (move via flagella, which are "whip-like" tails)
- Giardia lamblii or intestinalis
- Dientamoeba fragilis
- Chilomastrix mesnili
- Trichomonas vaginalis
- Hemoflagellate
- Leishmania spp
- Trypanosoma spp
- Amoeba (move via pseudopods, or "false feet")
- Class: (classified by means of locomotion, or how they move; unicellular)
- Phylum: Ciliophora:
- Class: Kinetofragminophorea:
- Ciliates (move via cilia, which are all over their body)
- Balantidium coli (only ciliate that is pathogenic to humans)
- Paramecium spp
- Ciliates (move via cilia, which are all over their body)
- Class: Kinetofragminophorea:
- Phylum: Apicomplexa:
- Class: Sporozoa:
- Class: Sporozoa:
- Coccidia (do not move at all)
- Cryptosporidium parvum
- Cyclospora cayetanesis
- Cystioisospora belli
- Blastocystis hominis
- Microsporidia spp
- Tissue Protozoan
- Pneumocystis jiroveci
- Toxoplasma gondii
- Pneumocystis jiroveci
- Coccidia (do not move at all)
- Phylum: Nemathelminthes
- Class: Nematoda (Nematodes or Roundworms)
- Enterobius vermicularis
- Trichuris trichiura
- Baylisascaris procyonis
- Ascaris lumbricoides
- Necator americanus
- Ancylostoma duodenale
- Necator americanus
- Trichostrongulus
- Strongyloides stercoralis
- Blood and Tissue Nematodes
- Trichinella spiralis
- Dracunculus medinensis
- Onchocerca volvulus
- Mansonella spp
- Wuchereria bancrofti
- Brugia malayi
- Loa loa
- Class: Nematoda (Nematodes or Roundworms)
- Phylum: Platyhelminthes (Flatworms and Flukes)
- Class: Cestoda/Cestodes
- Taenia saginata
- Taenia solium
- Hymenolepsis nana
- Hymenolepsis dimunita
- Diphyllobrothrium latum
- Diphylidium caninum
- Tissue Cestode
- Echinococcus spp
- Class: Digenea (Trematodes, Flukes)
- Fasciolopsis buski
- Fasciloa hepatica
- Paragonimus westermani
- Clonorchis sinensis
- Blood Flukes
- Schistosoma haematobium
- Schistosoma mansoni
- Schistosoma japonicum
- Class: Cestoda/Cestodes
- Phylum: Arthropoda (Arthropods)
- Class: Insecta (flies, mosquitoes, gnats, midges, bugs, fleas, lice, reduviid bugs)
- Chrysops fly
- Sand fly
- Black fly
- Tsetse fly
- Horse fly
- House fly
- Biting midges
- Reduviid bug
- Aedes aegyptus mosquito
- Anopheles spp mosquito
- Culex spp mosquito
- Mansonia species
- Fleas
- Chrysops fly
- Class: Arachnida (ticks, mites)
- Ixodes spp ticks
- Deer ticks
- Ixodes spp ticks
- Class: Insecta (flies, mosquitoes, gnats, midges, bugs, fleas, lice, reduviid bugs)
Parts of a parasitic life cycle:
There are at least 5 basic parts to every life cycle, which are important to be aware of:
- Parasitic stage and its location in the human host (example: intestines, bloodstream, tissue, lung, stomach, etc...) and if it is an egg, a larval stage, filaria, or adult.
- How the parasitic stage exits the host (example: sputum, feces, urine, blood, an insect bite or sucking of blood); Typically, this is the diagnostic stage and what is recovered in the laboratory and identified as by testing or microscopy.
- The infective stage and when the parasite is infective (example: egg, third-stage larvae), how it is transmitted or spread, and if any external development is required by the parasite for maturity
- The means in which a new human host becomes infected (example: fecal-oral route, insect bite, ingestion of contaminated food or water or soil, direct penetration into the skin)
- Sites of maturity of the parasite in its human host (Does it migrate?)
Aids in Identification and diagnostics regarding parasites:
Make sure to know and be able to write the following:
- The scientific name: (Genus, species): Example: Enterobius vermicularis
- The common name: Example: pinworm or seatworm
- The location of the mature adult in the human host: (Example: large intestines)
- The diagnostic stage: (Example: egg, worm, larvae)
- The body sample of choice: (Example: cellophane tape prep: Swube)
- The infective stage: (Example: egg, worm, larvae)
- Other information that is key and helpful and unique to each species (Examples: signs, symptoms, transmission, is it carried by a fomite or vector, is it infectious or contagious, how long does it live outside the human host, how is it treated, ways of prevention, if it is affected by time of day, light, dark, seasons, its normal habitat, etc...)
Measurements and size comparisons of ova (eggs) and cysts (courtesy the centers of disease control and prevention, dpdx, diagnostics):
clinical lab procedures for microbiological analysis of ova and parasites:
Important topics in Parasitology to begin with include the following:
- How to properly collect and transport specimens for analysis
- Safety and personal protective equipment (PPE)
- Routine examinations (ova and parasite exam; blood parasite exam)
- Macroscopic examination components
- Fresh, unpreserved stool
- Quality of the stool
- Color
- Consistency
- Blood or mucous
- Amount
- Means of collection
- Time of collection to time received at the lab
- Container, seal, bag
- Labels
- Fresh, unpreserved stool
- Microscopic examination components
- Direct (saline) wet mount
- Perform within 30 minutes to look for protozoan motility on fresh, unpreserved stool that is runny, liquid, or bloody (not hard or formed)
- Trophozoites start to break down and disintegrate after 30 minutes
- Perform within 30 minutes to look for protozoan motility on fresh, unpreserved stool that is runny, liquid, or bloody (not hard or formed)
- Direct (saline) wet mount with iodine
- Kills trophozoites and stalls motility
- Aids in observation of cysts (stains them)
- Kills trophozoites and stalls motility
- Pinworm Paddle (Swube)
- Preparing thick and thin blood smears and stains for blood parasites
- Giemsa and Wright stains
- Knott technique
- Ocular Micrometer
- The Trichrome Stain
- The Modified Acid-Fast Stain
- Direct (saline) wet mount
- Fecal concentration procedure
- Sedimentation method
- Flotation method
- Agar plate culture for Strongyloides stercoralis
- Immunoassays
- PCR
- Macroscopic examination components
The importance of proper specimen collection and transport procedures: why is it so important?
The ability to correctly and successfully detect and identify ova/eggs and parasites in stool or other types of specimens, including the detection and identification of protozoans, is directly proportional to the quality of the specimen submitted to Parasitology for evaluation and analysis. Therefore, successful diagnosis of parasitic diseases depends upon proper specimen collection and transport techniques, as well as knowing how to collect and transport samples, what types of samples are needed, when, and how many.
Successful diagnosis of intestinal parasitic diseases depends on collection of fresh stool that is collected and sent to the laboratory as soon as possible, and it is critical that it gets there within 30 minutes of collection. If the sample cannot be analyzed immediately, it should be properly preserved or fixed or refrigerated until it can be examined. In the next section, types of preservatives and the purpose of each are explained.
Before analyzing any stool or other sample, proper safety and PPE should be adhered to, including wearing gloves, labcoat or apron, a mask, working under a biological hood fitted with a HEPA filter, working slowly and carefully, placing biohazardous waste in proper waste containers, and properly cleaning up any spills or splashes right away and washing hands in between soiled gloves. Sticks, glass slides and coverslips, and anything sharp should be discarded of in properly marked sharps containers. OSHA refers to these as following "standard precautions" and treating all body fluids as if they were contaminated.
When receiving any sample, it should be properly labeled with at least 2 patient identifiers clearly and accurately marked, properly in containers and bags, and not leaking. The quality of the sample should be analyzed prior to testing the sample. This may require requesting a recollection of a sample that is not fit for analysis.
Successful diagnosis of intestinal parasitic diseases depends on collection of fresh stool that is collected and sent to the laboratory as soon as possible, and it is critical that it gets there within 30 minutes of collection. If the sample cannot be analyzed immediately, it should be properly preserved or fixed or refrigerated until it can be examined. In the next section, types of preservatives and the purpose of each are explained.
Before analyzing any stool or other sample, proper safety and PPE should be adhered to, including wearing gloves, labcoat or apron, a mask, working under a biological hood fitted with a HEPA filter, working slowly and carefully, placing biohazardous waste in proper waste containers, and properly cleaning up any spills or splashes right away and washing hands in between soiled gloves. Sticks, glass slides and coverslips, and anything sharp should be discarded of in properly marked sharps containers. OSHA refers to these as following "standard precautions" and treating all body fluids as if they were contaminated.
When receiving any sample, it should be properly labeled with at least 2 patient identifiers clearly and accurately marked, properly in containers and bags, and not leaking. The quality of the sample should be analyzed prior to testing the sample. This may require requesting a recollection of a sample that is not fit for analysis.
Specimen processing and quality of collection:
- The ability to correctly detect and identify ova/eggs and parasites in stool or other types of specimens, including the detection and identification of protozoans, is directly proportional to the quality of the specimen submitted to Parasitology for evaluation and analysis.
- The following things will interfere with testing of the specimen:
- Barium sulfate (radiologic studies)
- due to excess crystals in the stool specimen from this chemical
- may cause protozoa to remain undetectable for up to a week after use of barium
- may cause protozoa to remain undetectable for up to a week after use of barium
- due to excess crystals in the stool specimen from this chemical
- Mineral oil
- Bismuth ("Pepto Bismol")
- Antidiarrheal medications that are not absorbable
- Antimalarial drugs
- Some antibiotics, such as tetracycline
- for up to several weeks after the medication is stopped
- collect stool prior to starting antibiotics
- if stool is collected once antibiotics have been started, it must be rejected and resubmitted at least 2 weeks after therapy has ended
- for up to several weeks after the medication is stopped
- Contamination with urine
- may destroy motile organisms
- Contamination with toilet paper
- Contamination with tap or toilet water
- may contain free-living organisms that can cause a false-negative finding
- Barium sulfate (radiologic studies)
- Collect fresh stool in a clean container or white-capped Para-Pak container with no preservative
- A two-vial system is the standard means of transport for ova and parasite exams:
- Preserve in Cary-Blair (Green-Top Para-Pak) for certain exams such as GLCS, Biofire GI Panel
- Preserves stool up to 3 days at room temperature or refrigerated
- Preserve in 10% Formalin (Pink-Top Para-Pak) and PVA (Gray-Top Para-Pak) for concentration and stain (O & P exam) - this is the 2-vial system
- Formalin
- 8-10 mL (10%)
- Add 2-3 mL feces
- Use this vial for concentration, sedimentation, or zinc flotation methods
- It is an all-purpose fixative
- Easy to prepare
- Has a long shelf-life and can be kept a long time at room temperature
- Advantage is that it preserves the morphology of helminth eggs, cysts, larvae, coccidia, microsporidia and doesn't distort them
- Can be used to prepare the acid-fast stains for Cryptosporidium spp, Cyclospora spp
- Not useful for the Trichrome stain
- Doesn't really preserve the morphology of protozoan trophozoites
- Not able to be used for PCR
- PVA fixative
- 8-10 mL fixative containing polyvinyl alcohol
- Add 2-3 mL feces
- Use this one for Trichrome stains
- Helps the organisms to stick and adhere to the slides when preparing smears prior to staining
- Does a good job preserving the morphology of protozoan cysts and trophozoites
- Easy to prepare
- The preserved samples can be saved for several months
- Unable to use this vial for immunoassay kits or other permanent stains other than Trichrome
- Not as useful as formalin for concentration and sedimentation procedures
- When filling these with stool, fill to the "fill" line, properly label, and be sure to select the areas of the stool that are bloody, slimy, watery, or contain mucous
- Mix carefully and tightly cap and parafilm and place in a sealed biohazard bag.
- Formalin
- Preserve in Cary-Blair (Green-Top Para-Pak) for certain exams such as GLCS, Biofire GI Panel
- Pinworm Paddle for pinworm exam
- Also called a "Swube"
- Also called the "cellophane tape prep"
- Collect 3 samples, 2-3 days apart (one every other day), within a 10 day period for protozoan exams
- Collect at least 1-2 samples for a helminth exam
PRONUNCIATION OF PARASITES:
http://www.atsu.edu/faculty/chamberlain/website/studiop.htm
O & P exam = ova and parasite exam (usually 3 parts)
macroscopic exam:
Gross exam: This is a macroscopic exam, looking for visible eggs or cysts, worms, blood, mucus, pus, proglottids, and stool consistency and color (liquid, soft, formed, hard).
Liquid stool - examine within 30 minutes, since the trophozoites start to disintegrate after this
Semisolid stool - (soft) examine within 1 hour
Formed stool - examine within 24 hours or preserve by refrigeration for 1-2 days
Stool should thoroughly be examined with wooden sticks at the surface to the bottom. If you find any worms or proglottids, they should be fixed in 10% formalin first prior to examining them microscopically or preparing them to be sent out to a reference laboratory for examination.
Liquid stool - examine within 30 minutes, since the trophozoites start to disintegrate after this
Semisolid stool - (soft) examine within 1 hour
Formed stool - examine within 24 hours or preserve by refrigeration for 1-2 days
Stool should thoroughly be examined with wooden sticks at the surface to the bottom. If you find any worms or proglottids, they should be fixed in 10% formalin first prior to examining them microscopically or preparing them to be sent out to a reference laboratory for examination.
Microscopic exam:
- The routine microscopic exam consists of 3 distinct parts:
- Direct saline wet mount/prep
- Fecal concentration technique
- Permanently stained fecal smear
- Direct Saline Wet Mount/ Wet Prep:
- Perform within 2 hours of collection
- This is a rapid screening technique
- Perform on fresh stool, not preserved (see white top container)
- Using an applicator stick, mix a small bit of feces with a drop of saline on a clean slide and place a cover slip over it and view it immediately
- Using an applicator stick, mix a small bit of feces with a drop of saline on a clean slide and place a cover slip over it and view it immediately
- Perform saline wet mount first to look for trophozoites and MOTILITY
- Perform iodone wet mount with Lugol's iodine or D'Antoni's iodine for internal structures and cysts (vital stain), eggs, and larvae
- Be sure to look around the upper and side edges, because the heavier eggs and cysts tend to concentate here, and examine each field
- Examine 1/2 to 1/3 of the cover-slipped area under the 40x objective
- Examine 1/2 to 1/3 of the cover-slipped area under the 40x objective
- Turn the condenser and light down since many of these organisms and eggs are transparent
- Also document any of the following observed:
- Red blood cells
- White blood cells
- Charcot-Leyden crystals
- Red blood cells
- Direct Saline Wet Mount/ Wet Prep:
- Some laboratories and reference laboratories perform concentration and flotation and a permanent Trichrome Stain
the ocular micrometer:
In Parasitology, when a microscopic exam is performed, the ocular micrometer eyepiece should be put in place of one of the ocular eyepieces, and the ocular micrometer should be properly calibrated. Because there are considerable size differences in eggs, trophozoites, cysts, and larvae, they need to be measured for size for differentiation.
- Place the ocular micrometer in one of the eyepieces
- Place a stage micrometer on the microscope's stage
- Use the 10x objective to focus on the stage scale, which is 1 mm long, and is calibrated in 100ths (0.01 mm = 10 micrometers)
- Line the left edge of the ocular scale with the left edge of the stage scale (0 and 0 will line up)
- Find a point at the farthest point to the right where you see a line on the ocular micrometer superimposed on a line of the stage micrometer (example: 40 superimposed over 0.3)
- Calculate the number of micrometers indicated by each division on the ocular scale:
- # of stage micrometer spaces x 10 micrometers/number of ocular micrometer spaces = micrometer/ocular space
- Example: 30 x 10/40 = 7.5 um per ocular space
- # of stage micrometer spaces x 10 micrometers/number of ocular micrometer spaces = micrometer/ocular space
- Repeat the steps for each objective lens and record:
- 10x = 7.5 micrometers
- 40x = 3.0 micrometers
- 100x = 1.0 micrometers
- 10x = 7.5 micrometers
- Calibration should take place annually
Concentration and trichrome stain:
- Concentration Method:
- Performed from the pink-top 10% formalin preserved stool
- Goal is to concentrate the parasites, which this method increases the chances for recovery of, particularly when few are present
- Separates the parasites from fecal debris
- Flotation via Zinc and Specific Gravity (cysts at the top)
- Sedimentation via Centrifugation (debris sinks to bottom)
- Most common for concentrating eggs and cysts
- More efficient than flotation
- Results in about 2 g of sediment
- Stool layers:
- Top: ethyl acetate
- Next: fecal debris (rim this part off and discard after sedimentation)
- Middle: formalin
- Bottom: 2 g sediment, containing the parasites
- Top: ethyl acetate
- Most common for concentrating eggs and cysts
- Procedures: https://www.cdc.gov/dpdx/diagnosticprocedures/stool/specimenproc.html
- Permanent Slide Made From the Gray-Top Polyvinyl Alcohol (PVA)
- Preserves the trophozoites and cysts
- Make a trichrome stain (green background, cytoplasm is blue and the nuclear material is red)
- View under oil immersion
- Use the ocular micrometer to measure
Charcot leyden crystals
- Formed from eosinophils
- Eosinophil count is higher in association with a parasite infection (always check for correlations with other lab tests)
- Resemble "toothpicks" with 2 pointed ends that narrow at each end in Trichrome stains or acid-fast stains of concentrated fecal matter
Parasites:
Nematodes: Domain Eukarya, kingdom animalia, phylum nematoda:
Nematodes are part of Domain Eukarya, Kingdom animalia, Phylum nematoda. Nematodes are the roundworms. Named in 1861 for the Greek term "nema" meaning "thread", these worms are part of the metazoans. Nematodes are the most abundant animals on Earth, with >28,000 species! Their habitats include everything from soil to plants to sediment to marine to freshwater. Some are free-living, and others are parasitic.
When it comes to symmetry, there are three types of symmetry that describe Kingdom animalia: radial, bilateral and asymmetrical. Simple animals like sponges exhibit asymmetry and do not possess true tissues. Simple animals like the Cnidarians (jellyfish, hydra, medusa) exhibit radial symmetry and are referred to as diploblasts because they only possess 2 of the 3 types of body tissues: endoderm and ectoderm.
Nematodes are more complex, possess 3 types of body tissues: endoderm, mesoderm and ectoderm. For this reason, they are referred to as triploblasts. The nematode body plan, even though they are "round", is bilateral symmetry and they are referred to as "bilaterians". If you cut nematodes in half, each half "mirrors" the other exactly. They are cylindrical, elongate, and tapered at both ends.
Nematodes are pseudocoelomates. They possess a pseudocoelom, endoderm, mesoderm, ectoderm. They exhibit cephalization. The coelom is the main body cavity in the majority of animals. It is internal and surrounds and protects the digestive tract and its organs. In triploblast animals, it is lined with mesothelium. During embryonic development, the coelom develops during the gastrulation stage. The digestive tube develops from archenteron, a blind pouch.
Nematodes are Protostomes. In Protostomes, the coelom develops by a process called schizocoely. First, the blind pouch develops into an archenteron. Then, the mesoderm divides into 2 layers. The first layer attaches to the ectoderm, also known as the body wall. This forms the parietal layer. The second layer surrounds the endoderm. This is also called the alimentary canal. It forms what is known as the visceral layer. The gap or space between the visceral and parietal layer is known as the coelom (body cavity). A pseudocoelom is a "false body cavity". It is filled with fluid. The organs are held loosely, rather than firmly, in place by this fluid, which acts as a sort of cytoskeleton.
Nematodes range from microscopic to about 3 feet in length. The body has bristles, rings, ridges, a bilaterally symmetrical body and a radial symmetrical head with sensory bristles. Some of them have head shields (alae) radiating outwards around their mouth, which has 3-6 lips and often bears a series of teeth inside. They have a sticky, adhesive caudal gland at the tip of the tail. Their bodies are nonsegmented, vermiform. There is no circulatory or respiratory system. The cephalic end is the head, and the caudal end is the tail.
The epidermis is a single layer of cells (syncytium) covered by a thick, stronge yet flexible cuticle made of collagen. It is complex and has 2-3 distinct layers. It moults by the process known as ecdysis. Underneath it lies a layer of longitudinal muscle cells, and these plus the cuticle work together, along with the coelom fluid, to form a hydroskeleton. Internal projections run from the inner surface of muscle cells towards the nerve cords, making them a unique phyla.
The oral cavity is also lined with cuticle, often having ridges, plates or teeth, and a sharp stylet it can use to bear into its prey and suck liquids from prey or plants. It often contains a muscular sucking pharynx, lined with cuticle. It also consists of a large, bulbous esophagus. Internally, digestive glands are found and they produce enzymes that break down food. There is no stomach, but the pharynx connects directly to an intestine that forms the major length of the gut. It also produces digestive enzymes and absorbs nutrients through its single-cell thick lining.
There is also a rectum lined with cuticle and waste is excreted through the anus. The worm exhibits thrashing motions, which move food through the digestive system. There are sphincter valves at the ends of the intestines that also aid in movement of food through its body.
Waste is excreted as ammonia through its body wall. It also contains structures to excrete salt to maintain osmosis. One or two unicellular renette glands excrete salt through a pore underneath the worm, near the pharynx. Some have an organ with 2 parallel ducts connected by a transverse duct opening into a common canal running to an excretory pore instead to excrete salt.
Nematodes exhibit cephalization because they have 4 peripheral nerves that run along the length of their body on 3 surfaces: dorsal, ventral and lateral. Each of these nerves lies within a cord of connective tissue. This is just underneath the cuticle and between the muscle cells. Of the 3 nerves, the ventral nerve is the largest and controls motor movements. The lateral nerves are sensory. The ventral is the intermediate that combines both of the above functions. The cilia are also found in the nervous system of the nematode, which have a sensory, rather than motor, function. At the anterior end, the nerves branch into a nerve ring around the pharynx and act as a rudimentary “brain”. From here, there are smaller nerves that run toward the head to supply the sensory organs.The nematode body is also surrounded by sensory bristles and papillae that enable it to feel or have a sense of touch. On the head, there are 2 small pits (amphids) that are filled with nerve cells and act as chemoreceptors.
Most nematodes are separate sexes, but the soil nematode C. elegans is hermaphroditic. Both sexes possess 1-2 tube-shaped gonads. In males, the sperm are produced at the end of the gonad. They travel through the length of the worm during maturity. The testis empties into a large seminal vesicle. During copulation, the testis opens into a glandular and muscular ejaculatory duct linked wo the vas deferens and cloaca. In female worms, the ovaries open into an oviduct, then into a glandular uterus. The uterus opens into a common vulva, found in the middle of the ventral surface. Reproduction is sexual, but hermaphroditic types self-fertilize. Female worms are larger than male worms, and male worms tend to have a fan-shaped, bent tail. They also have spicules that move out of the cloaca, which are inserted into the genital pore of the female. The sperm are amoeboid and crawl along the spicule into the female worm. Eggs may be embryonated or unembryonated. Eggs hatch into larvae in free-living types.
Free-living nematodes feed on algae, fungi, bacteria, fecal matter, dead organisms, living tissue, and small animals. They are decomposers and recyclers, particularly in marine environments. They are also sensitive to pollution. Some benefit plants and some cause harm. Most of the soil nematodes enrich the top 6” of soil (topsoil). Both free-living and parasitic types reside here. They also play a key role in the nitrogen cycle.
Parasitic types to humans include the ascarids, filariae, hookworms, pinworms, whipworms, trichinellas. Some parasitize mammals, insects, or plants. In fact, one nematode parasitizes fig wasps, and they are the source of fig fertilization. They are the predators and the wasps are their prey, and they parasitize them from the ripe fig of the birth of the fig wasp to the fig flower when it kills them and their offspring. There is a nematode that parasitizes the tropical ant, causing it to develop bright red abdomen, be slow and sluggish, which attracts birds, who eat them, thinking they are berries, which spreads the nematode eggs. There are sweat bees parasitized by a nematode, which halts reproductive development in the female, causing her to be less active and can’t collect pollen effectively.
Nematophagous fungi are carnivorous fungi that are predators of nematodes and choke them by reaching out with adhesive structures and lassoing them at each end. These fungi create webs that trap the nematodes.
When it comes to symmetry, there are three types of symmetry that describe Kingdom animalia: radial, bilateral and asymmetrical. Simple animals like sponges exhibit asymmetry and do not possess true tissues. Simple animals like the Cnidarians (jellyfish, hydra, medusa) exhibit radial symmetry and are referred to as diploblasts because they only possess 2 of the 3 types of body tissues: endoderm and ectoderm.
Nematodes are more complex, possess 3 types of body tissues: endoderm, mesoderm and ectoderm. For this reason, they are referred to as triploblasts. The nematode body plan, even though they are "round", is bilateral symmetry and they are referred to as "bilaterians". If you cut nematodes in half, each half "mirrors" the other exactly. They are cylindrical, elongate, and tapered at both ends.
Nematodes are pseudocoelomates. They possess a pseudocoelom, endoderm, mesoderm, ectoderm. They exhibit cephalization. The coelom is the main body cavity in the majority of animals. It is internal and surrounds and protects the digestive tract and its organs. In triploblast animals, it is lined with mesothelium. During embryonic development, the coelom develops during the gastrulation stage. The digestive tube develops from archenteron, a blind pouch.
Nematodes are Protostomes. In Protostomes, the coelom develops by a process called schizocoely. First, the blind pouch develops into an archenteron. Then, the mesoderm divides into 2 layers. The first layer attaches to the ectoderm, also known as the body wall. This forms the parietal layer. The second layer surrounds the endoderm. This is also called the alimentary canal. It forms what is known as the visceral layer. The gap or space between the visceral and parietal layer is known as the coelom (body cavity). A pseudocoelom is a "false body cavity". It is filled with fluid. The organs are held loosely, rather than firmly, in place by this fluid, which acts as a sort of cytoskeleton.
Nematodes range from microscopic to about 3 feet in length. The body has bristles, rings, ridges, a bilaterally symmetrical body and a radial symmetrical head with sensory bristles. Some of them have head shields (alae) radiating outwards around their mouth, which has 3-6 lips and often bears a series of teeth inside. They have a sticky, adhesive caudal gland at the tip of the tail. Their bodies are nonsegmented, vermiform. There is no circulatory or respiratory system. The cephalic end is the head, and the caudal end is the tail.
The epidermis is a single layer of cells (syncytium) covered by a thick, stronge yet flexible cuticle made of collagen. It is complex and has 2-3 distinct layers. It moults by the process known as ecdysis. Underneath it lies a layer of longitudinal muscle cells, and these plus the cuticle work together, along with the coelom fluid, to form a hydroskeleton. Internal projections run from the inner surface of muscle cells towards the nerve cords, making them a unique phyla.
The oral cavity is also lined with cuticle, often having ridges, plates or teeth, and a sharp stylet it can use to bear into its prey and suck liquids from prey or plants. It often contains a muscular sucking pharynx, lined with cuticle. It also consists of a large, bulbous esophagus. Internally, digestive glands are found and they produce enzymes that break down food. There is no stomach, but the pharynx connects directly to an intestine that forms the major length of the gut. It also produces digestive enzymes and absorbs nutrients through its single-cell thick lining.
There is also a rectum lined with cuticle and waste is excreted through the anus. The worm exhibits thrashing motions, which move food through the digestive system. There are sphincter valves at the ends of the intestines that also aid in movement of food through its body.
Waste is excreted as ammonia through its body wall. It also contains structures to excrete salt to maintain osmosis. One or two unicellular renette glands excrete salt through a pore underneath the worm, near the pharynx. Some have an organ with 2 parallel ducts connected by a transverse duct opening into a common canal running to an excretory pore instead to excrete salt.
Nematodes exhibit cephalization because they have 4 peripheral nerves that run along the length of their body on 3 surfaces: dorsal, ventral and lateral. Each of these nerves lies within a cord of connective tissue. This is just underneath the cuticle and between the muscle cells. Of the 3 nerves, the ventral nerve is the largest and controls motor movements. The lateral nerves are sensory. The ventral is the intermediate that combines both of the above functions. The cilia are also found in the nervous system of the nematode, which have a sensory, rather than motor, function. At the anterior end, the nerves branch into a nerve ring around the pharynx and act as a rudimentary “brain”. From here, there are smaller nerves that run toward the head to supply the sensory organs.The nematode body is also surrounded by sensory bristles and papillae that enable it to feel or have a sense of touch. On the head, there are 2 small pits (amphids) that are filled with nerve cells and act as chemoreceptors.
Most nematodes are separate sexes, but the soil nematode C. elegans is hermaphroditic. Both sexes possess 1-2 tube-shaped gonads. In males, the sperm are produced at the end of the gonad. They travel through the length of the worm during maturity. The testis empties into a large seminal vesicle. During copulation, the testis opens into a glandular and muscular ejaculatory duct linked wo the vas deferens and cloaca. In female worms, the ovaries open into an oviduct, then into a glandular uterus. The uterus opens into a common vulva, found in the middle of the ventral surface. Reproduction is sexual, but hermaphroditic types self-fertilize. Female worms are larger than male worms, and male worms tend to have a fan-shaped, bent tail. They also have spicules that move out of the cloaca, which are inserted into the genital pore of the female. The sperm are amoeboid and crawl along the spicule into the female worm. Eggs may be embryonated or unembryonated. Eggs hatch into larvae in free-living types.
Free-living nematodes feed on algae, fungi, bacteria, fecal matter, dead organisms, living tissue, and small animals. They are decomposers and recyclers, particularly in marine environments. They are also sensitive to pollution. Some benefit plants and some cause harm. Most of the soil nematodes enrich the top 6” of soil (topsoil). Both free-living and parasitic types reside here. They also play a key role in the nitrogen cycle.
Parasitic types to humans include the ascarids, filariae, hookworms, pinworms, whipworms, trichinellas. Some parasitize mammals, insects, or plants. In fact, one nematode parasitizes fig wasps, and they are the source of fig fertilization. They are the predators and the wasps are their prey, and they parasitize them from the ripe fig of the birth of the fig wasp to the fig flower when it kills them and their offspring. There is a nematode that parasitizes the tropical ant, causing it to develop bright red abdomen, be slow and sluggish, which attracts birds, who eat them, thinking they are berries, which spreads the nematode eggs. There are sweat bees parasitized by a nematode, which halts reproductive development in the female, causing her to be less active and can’t collect pollen effectively.
Nematophagous fungi are carnivorous fungi that are predators of nematodes and choke them by reaching out with adhesive structures and lassoing them at each end. These fungi create webs that trap the nematodes.
Soil nematodes: the plant parasites
C. elegans is a model free-living soil nematode that is found in soil, rainwater, potted plants and plant water, moss in particular, and plays a role in the health of soil and in fermentation. Some strains are plant parasites, as seen in the images below.
Turbatrix aceti are free-living nematodes found in the "mother of vinegar" used to ferment apples into apple cider vinegar. They are also called "vinegar eels". They feed on microbial cultures, are found in biofilms, and were discovered in the 1600's by French scientist and botanist Pierre Borel.
These nematodes tolerate both acidity and alkalinity in a pH ranging from 1.6 to 11! These are harmless and non-parasitic. They are killed by pasteurization, but are found in unpasteurized cider and vinegar products. They play a key role, along with yeast and bacteria, in the fermentation process.
These nematodes tolerate both acidity and alkalinity in a pH ranging from 1.6 to 11! These are harmless and non-parasitic. They are killed by pasteurization, but are found in unpasteurized cider and vinegar products. They play a key role, along with yeast and bacteria, in the fermentation process.
Key Terminology in terms of nematodes and infections they can cause:
- Accidental host - incidental host; not the normal host for this parasite; the parasite may or may not complete maturity in the accidental host
- Apical complex - polar complex of secretory organelles
- Autoreinfection - an automatic reinfection of a host, such as in the pinworm (E. vermicularis) cycle, in which an infected individual reinfects themselves via hand-to-mouth transfer (fecal-oral route) of eggs deposited in the anal region, when scratching the area, then bringing the hand to one's mouth without hand hygiene. The eggs are infective, and may hatch inside the host, developing into adult worms, starting the life cycle over again.
- Buccal cavity - this is the mouth or oral region of the roundworm, which may contain hooks, teeth or cutting plates (hookworms) for the purpose of attachment
- Bursa - the caudal fan-shaped end of the male nematode that grasps the female during copulation
- Carrier - a host that harbors a parasite (reservoir) but does not exhibit any clinical signs or symptoms themselves but can "carry" or transmit it to someone else
- Caudal - tail region
- Cephalic - head region
- Commensalism - two different species live together, and one is benefited but the other is neither benefited nor harmed
- Copulatory spicules - the male nematode needle-like projection that remains in a pouch near the ejaculatory duct and is inserted into the female nematode genital pore during copulation to open it up
- Corticated - an egg that possesses an outermost albuminous coating, appearing lumpy rather than smooth
- Cutaneous larval migrans- "creeping eruption"; "ground itch"; occurs due to the migration of the larvae of the hookworm Ancylostoma species journeying just under the skin, leaving red papules and "tracks" that intensely itch
- Cuticle - the exterior, collagen-based, 2-3 layered cell coating of the nematode, which is flexible yet strong, tough and protective, which covers the surface of the nematode and is resistant to digestion, overlying several longitudinal muscle layers
- Definitive host - animal or individual in which the parasite matures into adulthood, reproduces sexually, or both
- Dermatiditis - inflammation and itching of the skin
- Diagnostic stage - Dx; the developmental stage of a pathogen that can be detected in the human host (feces, blood, body fluids, tissues, discharges) by tests or microscopy, in which identification aids in the diagnosis of the causative agent of the disease
- Differential diagnosis - clinical comparison of various diseases that exhibit similar signs, symptoms or patterns of disease to determine which one the host has
- Disease - illness; exhibiting characteristic symptoms and signs
- Diurnal - part of the parasitic life cycle which occurs during the daytime
- Ectoparasite - parasite living on a host
- Ecdysis - molting of the cuticle, which occurs several times during the larval stage, in which each larval stage is more mature than the one before, until reaching maturity
- Edema - fluid excess in tissue, resulting in swelling
- Elephantiasis - microfilarial infection by W. bancrofti, which infects the bloodstream, resulting the lymphatic system blockage, edema, gross overgrowth of the skin and subcutaneous tissues in the limbs beneath the lymphatic blockages by the worms, due to long-term, chronic infection
- Endoparasite - parasite living in a host
- Enteritis - intestinal inflammation, often with pain, bloating, gas, and diarrhea
- Eosinophilia - migrating nematodes are typically associated with this immune response, in which blood or tissue eosinophils are elevated
- Epidemiology - field of science that deals with relationships of hosts, parasites, dieases, factors that affect the frequency and severity of disease, distribution, transmission, spread and prevention of infectious disease in a community
- Esophagus - bulbar, large connection from the pharynx to the intestine in the nematode
- Facultative parasite - able to live independently (free-living) or as a parasite
- Fecundicity - reproductive ability, which is typically proportional to the complexity of the parasite's life cycle
- Fertilized egg - infective
- Filariae - infect blood or tissues; require an arthropod intermediate host to transmit infection to humans
- Filariform larvae - third-stage larvae; infective, nonfeeding, sheathed; have a long, slender esophagus; infection occurs via ingestion or penetration through the skin of the host or by the bite of an arthropod intermediate host
- Fomite - nonliving object that can transmit pathogens (combs, linens, clothing, bedding, doorknobs, water, food, etc...)
- Genus - genera; a taxonomic category (classification) given to a family, superior to species; it is always capitalized and italicized; groups organisms that are similar in broad features but vary in detail
- Gravid - pregnant or full of eggs, embryos, or larvae in the reproductive organs
- Heterogonic Life Cycle - free-living stage of the parasitic life cycle
- Homogonic Life Cycle - parasitic stage of the parasitic life cycle
- Host - species of plant, insect or animal that harbors a parasite
- Immunocompromisation - the immune response is compromised or depressed/decreased
- Incubation period - the period of time from initial infection through the appearance of clinical symptoms of disease
- Infection - invasion of the body by a pathogenic microbe, resulting in an immune response
- Infective stage - Ix; the stage of a parasitic life cycle in which the parasite can enter and mature within the host
- Infestation - establishment of arthropods on or in a host
- Intermediate host - animal in which a parasite passes its larval stage or an asexual reproductive phase
- In vitro - observable in the lab or in a test tube (nonliving)
- In vivo - within the living host
- Larvae - the immature stage of development of a nematode; molting occurs by ecdysis during this stage (several times) and each larval stage is more mature than the last
- Life cycle - infection, growth, development, maturity, reproduction, transmission of offspring to a new host
- Metazoaon - subkingdom of animals consisting of all multicellular animal organisms; cells differentiate to form tissues
- Microfilariae - embryonic stage of a filaria parasite, which is typically found in the blood or in the tissues of the human host; this stage can be ingested by the arthropod intermediate host and will develop within the arthropod into an infective larval stage (filaria)
- Molt - process in which the old cuticle is shed and replaced by a more mature one so that continued growth may occur and the larvae may continue to mature and develop
- Mutualism - both species benefit (cooperation)
- Nematode - roundworm; Phylum nematoda
- Obligatory parasite - cannot live apart from its host
- Occult - hidden (like blood in the stool)
- Parasitemia - presence of parasites in the bloodstream
- Parasitism - infected by a parasite; smaller species lives in or on a host and has a metabolic dependence upon the larger host species; the parasite is benefited and the host is harmed or injured
- Pathenogenic - capable of causing disease
- Pathogen - disease-causing agent
- Pathognomonic - disease; producing symptoms
- Periodicity - occurs at a regular time period (Circadian rhythm)
- Pica - craving nonedible items, such as dirt, ice, toilet paper, paper, chalk, paint; often seen in diseases linked to iron-deficiency anemia or pernicious anemia (vitamin B12 deficiency)
- Prepatent Period - the time gap between initial infection with larvae or infective eggs, and reproduction by the mature, adult parasite
- Pruritis - intense itching
- Rectal prolapse - rectal muscles weaken, resulting in prolapsis or "falling" of the rectum and anus, often occuring in heavy whipworm infections, particularly in children
- Reservoir - an animal that harbors a species of parasite that is also parasitic to humans and a human can become infected from it
- Rhabditiform larvae - noninfective larvae; feeding, first-stage larvae; hourglass-shaped esophagus
- Scientific name - generic name given to an organism that consists of the genus and species (specific epithet)
- Serology - tests that study the antibody-antigen resposne or reaction in vitro using host serum for study and antibody tests or assays
- Setae - papillae or bristles for sensory purposes that project from the surface of the nematode
- Species - always lowercase and italicized after the Genus; a taxonomic category or classification in which it stays in the same category and does not interbreed with others
- Symbiosis - residing together of two different species exhibiting metabolic dependence on each other by their relationship, so again, both benefit
- Transport host - animal harbors a parasite but it does not reproduce, so it is carried from one location to another to infect another host
- Tropical eosinophilia - high levels of blood eosinophils; asthma-like symptoms; related to filarial infections
- Vectors- arthropods or living carriers that transport a pathogenic organism from an infected host to a noninfected one; may transmit disease passively (mechanical) or may be an essential host in the life cycle of the parasite (biological vector)
- Visceral larval migrans - migration of the larval stage of the nematode Toxocara canas or T. cati through the lungs, liver, or other organs, resulting in hypereosinophilia and intense itching; migration to the eyes can cause retinal damage and blindness (ocular larval migrans)
- Zoonosis - disease involving a parasite that accidentally infected a human, but normally infects an animal
ova and parasites: the roundworms
Ascaris Lumbricoides-helminth: nematode: intestinal roundworm
Ascaris lumbricoides is an intestinal roundworm. Intestinal nematodes (roundworms) mature into adults in the human intestinal tract. The larval forms, though, may be distributed throughout the body. The human host with a normal, intact immune system rarely reacts to living worms, however, there is often a marked response to dead worms or helminth eggs. A marker of infection in the human body is eosinophilia, or a raised number of eosinophils in the blood seen during a CBC with differential. In fact, the percent eosinophilia ranges from 30-50% and is referred to as Loffler's syndrome. This hematology correlation assists in the diagnosis of the infection. Infection with this parasite is referred to as ascariasis (roundworm infection).
Infectious Stage and Phases of Infection:
Infection occurs via the ingestion of the eggs through contaminated foods. The eggs reach the small intestine, where larvae then emerge and penetrate through the intestinal wall. During the tissue phase, the larval forms migrate through the body and tissues until they reach the lungs, where they grow in the lung alveoli until they are coughed up and swallowed into the intestines. During the tissue phase, if there is heavy parasitemia, it can cause pneumonia with a cough and a low-grade fever. It takes about 1-2 weeks for the larvae to migrate to the lungs, at which time it may also trigger an allergic asthmatic reaction.
Diagnostic Stage:
After they are coughed up and swallowed, in the large intestines, the larvae mature into adult worms, producing more than 250,000 eggs per day! The eggs are then excreted in the feces. The eggs stay infections in soil or water for years! They are hearty and resistant to many chemicals. Finding and identifying eggs in the feces, corticated or uncorticated, fertile or nonfertile, is the diagnostic stage of this infection. Eggs are best recovered via sedimenation and concentration instead of flotation tests. There are serology tests that can also aid in diagnosis.
Infection Signs and Symptoms:
Infections tend to occur in tropical and mountainous areas of the southern USA, and may be asymptomatic or mild at first. Heavy infections may cause abdominal discomfort. Severe infections may involve adult worm penetration into the bile ducts, gallbladder, appendix and liver, which may then result in malnutrition because the worms are competing for and living off of the same nutrients as their human hosts. Masses of worms can actually cause intestinal blockages, appendicitis, and autoreinfection. Vomiting may also occur. The migrating adults can reach 22-35 cm in length, and can exit via the mouth, nose, or anus. Adult worms are white to cream-colored, with a cone-shaped tapered tail. The male has a curved tail.
Epidemiology:
Believe it or not, infection is actually endemic in much of the world. It is prevalent in warm countries and in areas where sanitation is not that great. This is an infection that can coexist with whipworm (T. trichiura). In the USA, it is found mainly in the Appalachian Mountains. The eggs are found in the soil.
Facts:
Ascaris lumbricoides is the largest adult intestinal nematode. It is the second most common intestinal helminth infection in the USA and THE most common worldwide.
Migration of the worms increases when exposed to certain drugs, including anesthesia, and can become entangled in the intestines, resulting in blockages. Complications can be deadly.
Macroscopic and Microscopic Appearance:
Laboratory diagnosis is made by identification of eggs in the feces and/or the sputum, and by eosinophilia on a blood smear, or by findings of the pink or white worms.
Adult female worm: 20-35 cm
Male worm: 15-31 cm with a curved tail
Fertile eggs: 45-75 microns by 35-50 microns with an outer, coarse, wavy covering with a thick, transparent, hyaline shell and thick outer layer (corticated or uncorticated)
Infertile eggs: elongated 88-94 microns by 39-44 microns with a thinner shell.
Treatment:
Treatments include Mebendazole, Peperazine citrate, Levamisole, Corticosteroids, Thiabendazole or Albendazole, which basically paralyze the roundworms so they are excreted in the stool. An alternative drug is Pyrantel pamoate.
Infectious Stage and Phases of Infection:
Infection occurs via the ingestion of the eggs through contaminated foods. The eggs reach the small intestine, where larvae then emerge and penetrate through the intestinal wall. During the tissue phase, the larval forms migrate through the body and tissues until they reach the lungs, where they grow in the lung alveoli until they are coughed up and swallowed into the intestines. During the tissue phase, if there is heavy parasitemia, it can cause pneumonia with a cough and a low-grade fever. It takes about 1-2 weeks for the larvae to migrate to the lungs, at which time it may also trigger an allergic asthmatic reaction.
Diagnostic Stage:
After they are coughed up and swallowed, in the large intestines, the larvae mature into adult worms, producing more than 250,000 eggs per day! The eggs are then excreted in the feces. The eggs stay infections in soil or water for years! They are hearty and resistant to many chemicals. Finding and identifying eggs in the feces, corticated or uncorticated, fertile or nonfertile, is the diagnostic stage of this infection. Eggs are best recovered via sedimenation and concentration instead of flotation tests. There are serology tests that can also aid in diagnosis.
Infection Signs and Symptoms:
Infections tend to occur in tropical and mountainous areas of the southern USA, and may be asymptomatic or mild at first. Heavy infections may cause abdominal discomfort. Severe infections may involve adult worm penetration into the bile ducts, gallbladder, appendix and liver, which may then result in malnutrition because the worms are competing for and living off of the same nutrients as their human hosts. Masses of worms can actually cause intestinal blockages, appendicitis, and autoreinfection. Vomiting may also occur. The migrating adults can reach 22-35 cm in length, and can exit via the mouth, nose, or anus. Adult worms are white to cream-colored, with a cone-shaped tapered tail. The male has a curved tail.
Epidemiology:
Believe it or not, infection is actually endemic in much of the world. It is prevalent in warm countries and in areas where sanitation is not that great. This is an infection that can coexist with whipworm (T. trichiura). In the USA, it is found mainly in the Appalachian Mountains. The eggs are found in the soil.
Facts:
Ascaris lumbricoides is the largest adult intestinal nematode. It is the second most common intestinal helminth infection in the USA and THE most common worldwide.
Migration of the worms increases when exposed to certain drugs, including anesthesia, and can become entangled in the intestines, resulting in blockages. Complications can be deadly.
Macroscopic and Microscopic Appearance:
Laboratory diagnosis is made by identification of eggs in the feces and/or the sputum, and by eosinophilia on a blood smear, or by findings of the pink or white worms.
Adult female worm: 20-35 cm
Male worm: 15-31 cm with a curved tail
Fertile eggs: 45-75 microns by 35-50 microns with an outer, coarse, wavy covering with a thick, transparent, hyaline shell and thick outer layer (corticated or uncorticated)
Infertile eggs: elongated 88-94 microns by 39-44 microns with a thinner shell.
Treatment:
Treatments include Mebendazole, Peperazine citrate, Levamisole, Corticosteroids, Thiabendazole or Albendazole, which basically paralyze the roundworms so they are excreted in the stool. An alternative drug is Pyrantel pamoate.
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Ascaris lumbricoides-Adult Worm. Worms are conically tapered at the ends as seen in the image above. The female measures 22-35 cm in length, whereas the male measures 10-31 cm in length with a sharply curved tail with 2 copulary spicules. Adult worms live in the small intestine and can survive for more than a year. Females lay up to 200,000 eggs a day. The first sign of infection is usually passage of the adult worms with the feces. Heavy infections may cause pneumonia, diarrhea, vomiting or bowel obstruction. Perforation of the intestinal wall or appendix, peritonitis, or airway obstruction by the worms may occur with heavy infection, and may even result in death.
Ancylostoma duodenale & braziliense-Old world hookworms
Ancylostoma braziliense causes hookworm disease, or cutaneous larval migrans infections and allergic dermatitis called "creeping eruptions" or "cutaneous larval migrans". Infection with this worm results in intense itching and a red papule with a tunnel where the larvae entered and traveled, moving a few mm per day. These are often called "tracks".
Infections commonly occur in the southeastern USA, particularly where there is affected sand on the Atlantic coast from NJ to FL, along the Gulf of Mexico, parts of TX, and in the midwest, and are caused by the migration of the larvae of dog and cat hookworms into the human host skin, where they migrate underneath the epidermis. The larvae typically move a few centimeters each day, and their presence mounts a huge immune response resulting in an itchy, raised, red rash that moves to different areas of the body with the advancing movement of the larvae.
Larvae can migrate all the way to the lungs, which may result in an intra-alveolar hemorrhage, mild pneumonia, cough, wheezing, sore throat, sputum with blood in it, and a headache. This may also result in high eosinophilia.
During the intestinal phase of infection, the worms may either be in an acute or a chronic phase of infection. If acute, the individual produces a heavy worm burden, resulting in enteritis, epigastric distress in around a third to one half of infected individuals, loss of appetite, nausea, pain, diarrhea, anemia, weakness, swelling, weakness, blood loss, and hypoproteinemia. If the infection is chronic, there is a lighter worm burden, milk anemia, weakness, weight loss, and mild gastroenteritis.
Infection tends to occur by walking around in bare feet, where the larvae penetrate the skin directly. Those with heavy parasitemia may also experience nausea, fatigue, diarrhea, weight loss, anemia and abdominal pain along with the itching. In children, physical and mental development may also be affected. Eggs are deposited in the stool, where they then can hatch into larvae (worms) which can penetrate the skin.
The pairs of teeth in the buccal cavity of the Ancylostoma duodenale hookworm allow for firm attachment to the mucosa of the small intestine. The blood-sucking activity of the worms can also result in a hypochromic microcytic anemia (iron-deficiency) in addition to other symptoms. Male worms are 1 cm by 0.5 mm and females are slightly longer. They thrive in warm soil.
Diagnosis is based on biopsy of the advancing edge of the rash, examination of eggs or worms passed in the stool via macroscopic and microscopic examination, and peripheral blood smear.
The images below are iodine and saline wet mounts of the parasitic hookworm, fertilized eggs and mature eggs (ova/cysts).
Microscopic Exam Appearance:
Infections commonly occur in the southeastern USA, particularly where there is affected sand on the Atlantic coast from NJ to FL, along the Gulf of Mexico, parts of TX, and in the midwest, and are caused by the migration of the larvae of dog and cat hookworms into the human host skin, where they migrate underneath the epidermis. The larvae typically move a few centimeters each day, and their presence mounts a huge immune response resulting in an itchy, raised, red rash that moves to different areas of the body with the advancing movement of the larvae.
Larvae can migrate all the way to the lungs, which may result in an intra-alveolar hemorrhage, mild pneumonia, cough, wheezing, sore throat, sputum with blood in it, and a headache. This may also result in high eosinophilia.
During the intestinal phase of infection, the worms may either be in an acute or a chronic phase of infection. If acute, the individual produces a heavy worm burden, resulting in enteritis, epigastric distress in around a third to one half of infected individuals, loss of appetite, nausea, pain, diarrhea, anemia, weakness, swelling, weakness, blood loss, and hypoproteinemia. If the infection is chronic, there is a lighter worm burden, milk anemia, weakness, weight loss, and mild gastroenteritis.
Infection tends to occur by walking around in bare feet, where the larvae penetrate the skin directly. Those with heavy parasitemia may also experience nausea, fatigue, diarrhea, weight loss, anemia and abdominal pain along with the itching. In children, physical and mental development may also be affected. Eggs are deposited in the stool, where they then can hatch into larvae (worms) which can penetrate the skin.
The pairs of teeth in the buccal cavity of the Ancylostoma duodenale hookworm allow for firm attachment to the mucosa of the small intestine. The blood-sucking activity of the worms can also result in a hypochromic microcytic anemia (iron-deficiency) in addition to other symptoms. Male worms are 1 cm by 0.5 mm and females are slightly longer. They thrive in warm soil.
Diagnosis is based on biopsy of the advancing edge of the rash, examination of eggs or worms passed in the stool via macroscopic and microscopic examination, and peripheral blood smear.
The images below are iodine and saline wet mounts of the parasitic hookworm, fertilized eggs and mature eggs (ova/cysts).
Microscopic Exam Appearance:
- Hookworm: has a thick body and 4 sharp suckers resembling "fangs" (sharp teeth)
- Mature eggs (ova/cyst):
- worm is curled up inside the thick oval hyaline shell
- 60 by 40 micrometers
- worm is curled up inside the thick oval hyaline shell
- Fertilized eggs (ova/cyst):
- pack of 4-8 blastomeres inside a large oval hyaline shell
- 60 by 40 micrometers
Necator americanus: new world hookworm
The new world hookworm Necator americanus is similar to Ancylostoma. It is found in North and South America, Asia, and Africa. It is more common in areas with poor sanitation. It is estimated that around 25% of the world's population is infected with this organism.
Hookworms are prevalent in warm, moist areas and sandy soil. Fecal examination should occur immediately because the larvae can develop quickly and eggs can hatch, and the hookworm larvae must be differentiated from Strongyloides stercoralis larvae.
Hookworm rhabditoform larvae have a long buccal capsule and new world hookworm has a pair of semilunar cutting plates (top and bottom).
Hookworms are prevalent in warm, moist areas and sandy soil. Fecal examination should occur immediately because the larvae can develop quickly and eggs can hatch, and the hookworm larvae must be differentiated from Strongyloides stercoralis larvae.
Hookworm rhabditoform larvae have a long buccal capsule and new world hookworm has a pair of semilunar cutting plates (top and bottom).
strongyloides stercoralis: threadworm
Strongyloides stercoralis is known as threadworm. It causes strongyloidiasis or threadworm infection. The identification of and recovery of the first-stage larvae (rhabditiform larvae) in the stool is diagnostic for this organism.
The eggs resemble hookworm eggs or larvae and may be recovered in duodenal aspirates. Larvae are also sometimes recovered in sputum samples. In heavy worm burden cases, intestinal radiology tests may indicate a loss of mucosal pattern, rigidity and narrowing of the tubules.
Rhabditiform larvae are unique because they have short buccal capsules, a bulbar esophagus, and prominent genital primordium.
Symptoms:
Symptoms include abdominal pain, diarrhea, urticaria (hives), and eosinophilia. There may also be a skin reaction, including allergic, itchy wheals (hives) where the larvae penetrate the skin. As the larvae migrate, there may be bronchitis symptoms if they reach the lungs, which may even progress to pneumonia.
Migration to the intestines during the intestinal phase results in diarrhea and constipation, abdominal pain, vomiting, loss of appetite and weight, anemia, eosinophilia, and hypoproteinemia. Some infections may remain asymptomatic if they are very light. But in heavy infections, the bowel may appear swollen and congested. Heavy autoinfection in immunocompromised individuals has even resulted in mortality and larval migration throughout the body, along with secondary bacterial infection, and intestinal perforation resulting in peritonitis.
Treatment is a choice of Thiabendazole, Albendazole or Ivermectin.
This nematode thrives in warm, tropical and subtropical regions worldwide.
The female worm is parthenogenic, so she can multiply rapidly, causing autoreinfection or hyperinfection in the same host. For this reason, this infection can be difficult to treat and eradicate. The life cycle of this worm is heterogonic and homogonic, meaning it has a free-living stage and a parasitic stage.
Diagnosis consists of using the sedimentation and concentration technique rather than flotation to recover eggs and rhabditiform larvae in the stool. The first-stage rhabditiform larvae is differentiated from hookworm rhabditiform larvae by noting the short buccal capsule, prominent genital primordium, and bulbar-shaped esophagus.
The eggs resemble hookworm eggs or larvae and may be recovered in duodenal aspirates. Larvae are also sometimes recovered in sputum samples. In heavy worm burden cases, intestinal radiology tests may indicate a loss of mucosal pattern, rigidity and narrowing of the tubules.
Rhabditiform larvae are unique because they have short buccal capsules, a bulbar esophagus, and prominent genital primordium.
Symptoms:
Symptoms include abdominal pain, diarrhea, urticaria (hives), and eosinophilia. There may also be a skin reaction, including allergic, itchy wheals (hives) where the larvae penetrate the skin. As the larvae migrate, there may be bronchitis symptoms if they reach the lungs, which may even progress to pneumonia.
Migration to the intestines during the intestinal phase results in diarrhea and constipation, abdominal pain, vomiting, loss of appetite and weight, anemia, eosinophilia, and hypoproteinemia. Some infections may remain asymptomatic if they are very light. But in heavy infections, the bowel may appear swollen and congested. Heavy autoinfection in immunocompromised individuals has even resulted in mortality and larval migration throughout the body, along with secondary bacterial infection, and intestinal perforation resulting in peritonitis.
Treatment is a choice of Thiabendazole, Albendazole or Ivermectin.
This nematode thrives in warm, tropical and subtropical regions worldwide.
The female worm is parthenogenic, so she can multiply rapidly, causing autoreinfection or hyperinfection in the same host. For this reason, this infection can be difficult to treat and eradicate. The life cycle of this worm is heterogonic and homogonic, meaning it has a free-living stage and a parasitic stage.
Diagnosis consists of using the sedimentation and concentration technique rather than flotation to recover eggs and rhabditiform larvae in the stool. The first-stage rhabditiform larvae is differentiated from hookworm rhabditiform larvae by noting the short buccal capsule, prominent genital primordium, and bulbar-shaped esophagus.
Trichinella spiralis (trichinosis; trichinellosis)
Trichinella spiralis is a parasite of pigs, rats, bears, and walruses that can accidentally infect humans if they consume undercooked or raw meat infected with the organism. Larvae encyst in muscles as seen in the images below. Therefore, diagnosis occurs by analyzing biopsied muscle tissue, using serology testing. It takes about 3-4 weeks for the larvae to encyst in muscle tissues. It results in edema and swelling. It is also associated with eosinophilia. Infection is known as trichinosis or trichinellosis.
During the intestinal phase, the small intestine swells and becomes inflamed, resulting in nausea, vomiting, abdominal pain, diarrhea, headach, and fever. This occurs within 1 week of infection.
The migration phase is next. During this phase, the fever grows higher, swelling occurs behind the eye sockets (periorbital edema), resulting in blurred vision, increased headaches, swelling of the face and eyes, pleurisy, cough, and increased eosinophilia. This phase lasts for about a month on average. Death can occur at this time after 1-2 months of infection.
Lastly, the muscular phase results in acute inflammation, muscle pain and swelling. Symptoms depend upon where the worms encyst in the muscles. Infected muscle cells are known as "nurse cells". The nurse cell forms when the larvae penetrates the striated muscle cells by releasing enzymes that enable it to bore through. A granuloma is formed to "hide" and protect it from immune destruction, which calcifies and hardens over time. During this phase, fatigue and weakness ensue.
Focal lesions also result in splintering hemorrhages of the nails, hemorrhages of the retina, and skin rashes. If the infection is mild, it is self-limiting and treated with rest, fever and pain medication, and fluids. If the infection is heavy and severe, corticosteroids to suppress the immune response and Thiabendazole are given.
Distribution is worldwide but prevalence is rare in the USA. It is more common in areas such as Alaska and the Arctic where rare and undercooked meats are eaten more frequently.
During the intestinal phase, the small intestine swells and becomes inflamed, resulting in nausea, vomiting, abdominal pain, diarrhea, headach, and fever. This occurs within 1 week of infection.
The migration phase is next. During this phase, the fever grows higher, swelling occurs behind the eye sockets (periorbital edema), resulting in blurred vision, increased headaches, swelling of the face and eyes, pleurisy, cough, and increased eosinophilia. This phase lasts for about a month on average. Death can occur at this time after 1-2 months of infection.
Lastly, the muscular phase results in acute inflammation, muscle pain and swelling. Symptoms depend upon where the worms encyst in the muscles. Infected muscle cells are known as "nurse cells". The nurse cell forms when the larvae penetrates the striated muscle cells by releasing enzymes that enable it to bore through. A granuloma is formed to "hide" and protect it from immune destruction, which calcifies and hardens over time. During this phase, fatigue and weakness ensue.
Focal lesions also result in splintering hemorrhages of the nails, hemorrhages of the retina, and skin rashes. If the infection is mild, it is self-limiting and treated with rest, fever and pain medication, and fluids. If the infection is heavy and severe, corticosteroids to suppress the immune response and Thiabendazole are given.
Distribution is worldwide but prevalence is rare in the USA. It is more common in areas such as Alaska and the Arctic where rare and undercooked meats are eaten more frequently.
Dracunculus medinensis: guinea worm
Dracunculus medinensis is the largest adult nematode parasite in humans. It does not occur in the USA. Infection is called dracunculus or Guinea worm. This painful infection results in a painful lesion or ulceration with the emerging worm. Application of cold water will provoke it to emerge, then slow removal is necessary over a period of days-to-weeks-to-months by slowly wrapping it around a stick. Sometimes surgery is required to remove an adult worm.
Due to the migration of the larvae, an allergic response is provoked, often with eosinophilia. Due to the nature of the blister formation, eruption, and ulceration, secondary bacterial infection is common. Ulcerations tend to affect the foot or leg after the initial papule where the worm entered blister and erupt.
Humans become infected if they ingest contaminated water with infected copepods, which mature into larvae and migrate to the abdominal cavity, where they develop and mature. The female worm then migrates into the subcutaneous tissue and releases larvae, which exit the human host via the ruptured ulceration of the skin. Larvae then enter the water where they are ingested by copepods, which serve as intermediate hosts. The copepods are of the Cyclops species (see below).
Due to the migration of the larvae, an allergic response is provoked, often with eosinophilia. Due to the nature of the blister formation, eruption, and ulceration, secondary bacterial infection is common. Ulcerations tend to affect the foot or leg after the initial papule where the worm entered blister and erupt.
Humans become infected if they ingest contaminated water with infected copepods, which mature into larvae and migrate to the abdominal cavity, where they develop and mature. The female worm then migrates into the subcutaneous tissue and releases larvae, which exit the human host via the ruptured ulceration of the skin. Larvae then enter the water where they are ingested by copepods, which serve as intermediate hosts. The copepods are of the Cyclops species (see below).
Protozoans: ciliated protozoans and intestinal flagellates:
Important Terminology and Facts:
Atria (atrium) - an opening, such as the mouth, anus, urethra, genital pore
Axoneme - central interior part of a flagellum
Axostyle - a supportive axial rod in flagellates
Balantidiasis - disease produced by the pathogenic ciliate Balantidium coli causing abdominal pain and discomfort, milk to moderate, chronic, recurrent diarrhea or acute dysentery
Binary fission - asexual reproduction by splitting in half
Cilia - ectoplasmic, hair-like structures attached to the surface of the cell that aid in movement or sensory functions
Ciliophora - phylum consisting of protozoans that move via cilia for motility; have 2 different types of nuclei
Costa - a firm, thin, rod-like structure that runs at the base/bottom of the undulating membrane on various types of flagellates
Cyst - nonactive resting stage
Cytostome - a mouth
Dysentery - diarrhea, often with blood and/or mucous
Flagellates - pathogenic and nonpathogenic gastroinestinal or vaginal protozoans that use flagella for motility
Pathogenic GI:
Kinetofragminophorea - the class of protozoans that utilize cilia for motility
Mastigophora - superclass consisting of flagellates in class zoomastigophorea and ciliates in class kinetofragminoporea
Precyst - a phase in which a protozoan produces a resting cyst to store products and stop feeding until conditions become favorable again
Sucking disk - concave structure on the ventral side of some protozoans as a means of attachment to the intestinal mucosa
Trophozoite - active, motile, feeding form of certain protozoans
Undulating membrane - a protoplasmic membrane produced by some protozoans in which the flagellar rim projects outward like a fin and moves in a wavelike pattern for motility
Vacuole - storage structure for glycogen, pigments, iron, and other things
Zoomastigophorea - class of protozoans that utilize flagella for motility
Atria (atrium) - an opening, such as the mouth, anus, urethra, genital pore
Axoneme - central interior part of a flagellum
Axostyle - a supportive axial rod in flagellates
Balantidiasis - disease produced by the pathogenic ciliate Balantidium coli causing abdominal pain and discomfort, milk to moderate, chronic, recurrent diarrhea or acute dysentery
Binary fission - asexual reproduction by splitting in half
Cilia - ectoplasmic, hair-like structures attached to the surface of the cell that aid in movement or sensory functions
Ciliophora - phylum consisting of protozoans that move via cilia for motility; have 2 different types of nuclei
- Micronucleus - small
- Macronucleus - large, kidney-shaped
Costa - a firm, thin, rod-like structure that runs at the base/bottom of the undulating membrane on various types of flagellates
Cyst - nonactive resting stage
Cytostome - a mouth
Dysentery - diarrhea, often with blood and/or mucous
Flagellates - pathogenic and nonpathogenic gastroinestinal or vaginal protozoans that use flagella for motility
Pathogenic GI:
- Giardia lamblia (duodenalis) - "traveler's diarrhea" (lots of mucous)
- Most common intestinal protozoan in the USA
- Cyst stage
- Oval
- 2-4 nuclei at one end, clustered
- Central axoneme
- Looks like a "little old lady wearing glasses" or "an old man with whiskers"
- Cytoplasm is often retracted from the cell wall
- Trophozoite stage
- Bilateral symmetry
- 2 anterior nuclei
- 8 flagella
- Sucking disk
- Adhere to mucosal wall (duodenum)
- Intermittant shedding
- Heavy infection
- Diarrhea with lots of mucous
- Malabsorption (loss of vitamin B12 and iron)
- Referred to as giardiasis or traveler's diarrhea
- Symptoms:
- Abdominal pain
- Foul odor (diarrhea) and gas and belching
- Bloating
- Intestinal inflammation and malabsorption
- May lead to secondary perniceous and iron-deficiency anemia
- Initial symptoms last a few days
- Transmission
- Fecal-oral route (contaminated water or food)
- Worldwide distribution
- Commonly occurs during travel to endemic areas
- This organism can survive chlorinated water for up to 45 minutes, which is why evacuating fecally contaminated swimming pools is so important
- Outbreaks:
- Oubreaks have occurred due to cross-contamination of water and sewage during water main breaks, contamination of streams by wild animals like beavers, after natural disasters like hurricanes
- Diagnosis:
- Should examine at least THREE stool samples due to the intermittant shedding of cysts and/or trophozoites
- Prepare and examine a permanent stained smear (Trichrome)
- Examine the mucous areas of the stool
- String test
- Antigen-based immunoassays
- The Biofire microfilmarray can identify this with PCR rapidly
- Fecal leukocytes and occult blood tests will be negative
- Treatment:
- Metronidazole
- Furazolidone
- Quinacrine
- Giardia intestinalis
- Dientamoeba fragilis
- Illness:
- Typically asymptomatic
- May cause diarrhea, abdominal pain, and loss of appetite
- Habitat:
- Colon and cecum
- Transmission:
- Uncertain
- Distribution is worldwide
- Can be transmitted with other parasites, including pinworm (E. vermicularis) and roundworm (A. lumbricoides), since they inhabit the same soil conditions
- Precyst:
- Up to 10 micrometers
- Rarely seen in stained fecal smears
- 2 nuclei, each with a large karyosome, in center of the cell
- Cyst:
- Axostyle
- Flagellar axonemes (lost upon excystation)
- Costa
- 4-5 micrometers
- Trophozoite:
- 2 nuclei connected by a spindle filament
- No observable flagella
- Phylum Parabasala, Class Trichomonadea
- Motility: Pseudopodia
- 6-20 micrometers
- Sluggish, nondirectional motility
- Diagnosis:
- Identification of trophozoites in fresh stool
- At least THREE stool samples should be examined
- A permanently stained smear should be examined
- This is one of the few samples in which trophozoites can be found in formed stools (in other species, they die within 30 minutes)
- Treatment:
- Iodoquinol
- Tetracycline
- Paromomycin
- Illness:
- Chilomastix mesneli
- Cyst:
- Clear knob on anterior end
- Single nucleus with central karyosome
- Cytosome
- Trophozoite:
- Anterior nucleus with central karyosome
- 4 anterior flagella
- Cytosomal groove
- Curved posterior tail
- Cyst:
- Trichomonas hominis
- Enteromonas hominis
- Retortamonas intestinalis
- Trichomonas vaginalis
- Habitat: Genitourinary tract (multiplies here)
- Symptoms:
- Women experience symptoms more so than men
- Trichomoniasis - primary nonviral STD in the world
- Vaginal inflammation
- Yellowish, greenish, frothy, foul-smelling discharge
- Burning urination
- Itching and irritation
- Men may be asymptomatic carriers
- Women experience symptoms more so than men
- Transmission:
- Sexual contact
- Cases:
- Worldwide (>275 million cases anually)
- USA (7-8 million)
- Asymptomatic: up to 50%
- Cyst: no cyst stage
- Trophozoite:
- Motile
- Fresh urine or secretions (discharges)
- Characteristic jerky, rippling motion
- Large anterior nucleus
- 4 anterior flagella
- Axostyle
- Undulating membrane
- Treatment:
- Metronidazole (Flagyl)
- Trichomonas tenax
- P. hominis
- May be found as a fecal contaminant in urine samples
- Monotrichous- unipolar; one at one end
- Amphitrichous - bipolar; one at each end
- Lophotrichous - tuft or cluster of flagella at one end
- Peritrichous - covering the entire surface in all directions
Kinetofragminophorea - the class of protozoans that utilize cilia for motility
Mastigophora - superclass consisting of flagellates in class zoomastigophorea and ciliates in class kinetofragminoporea
Precyst - a phase in which a protozoan produces a resting cyst to store products and stop feeding until conditions become favorable again
Sucking disk - concave structure on the ventral side of some protozoans as a means of attachment to the intestinal mucosa
Trophozoite - active, motile, feeding form of certain protozoans
Undulating membrane - a protoplasmic membrane produced by some protozoans in which the flagellar rim projects outward like a fin and moves in a wavelike pattern for motility
Vacuole - storage structure for glycogen, pigments, iron, and other things
Zoomastigophorea - class of protozoans that utilize flagella for motility
Balantidium coli-balantidiasis
The only ciliated protozoan that causes infection in humans is Balantidium coli. Distribution is worldwide, however, it infection is rare in the USA. Pigs are natural reservoirs of the parasite.
Infection and Symptoms:
Balantidium coli infection causes diarrhea in an infection known as balantidiasis or balantidial dysentery. Infections result from eating or drinking foods or water contaminated with the parasite cyst forms, which mature into ciliated trophozoites. The trophozoites travel to the GI tract, boring through the intestinal wall into the submucosa, and live off of the commensal microbiota that live there. Most persons remain asymptomatic, but some develop diarrhea, abscesses, ulcers, or even gangrene.
Structure:
Balantidium coli trophozoites are the largest and only ciliated protozoan parasites found in the intestines and diagnosis is made by finding the cysts or trophozoites on an O & P exam in fecal specimens, as seen in the images below. Their size is about 60 micrometers x 40 micrometers! Their means of locomotion, or movement, is via cilia, hairlike structures found all over their body.
Microscopic Exam Characteristics:
Treatment is typically tetracycline, which tends to be an effective medication for treating this infection. Other treatments may include metronidazole or iodoquinol.
Infection and Symptoms:
Balantidium coli infection causes diarrhea in an infection known as balantidiasis or balantidial dysentery. Infections result from eating or drinking foods or water contaminated with the parasite cyst forms, which mature into ciliated trophozoites. The trophozoites travel to the GI tract, boring through the intestinal wall into the submucosa, and live off of the commensal microbiota that live there. Most persons remain asymptomatic, but some develop diarrhea, abscesses, ulcers, or even gangrene.
Structure:
Balantidium coli trophozoites are the largest and only ciliated protozoan parasites found in the intestines and diagnosis is made by finding the cysts or trophozoites on an O & P exam in fecal specimens, as seen in the images below. Their size is about 60 micrometers x 40 micrometers! Their means of locomotion, or movement, is via cilia, hairlike structures found all over their body.
Microscopic Exam Characteristics:
- Trophozoite: gray-green, ovoid, sac-shaped, 30-150 microns by 25-120 microns
- Cyst: green-yellow, sub spherical or oval, double-walled, macro-nucleus, contractile vacuoles, cilia, ranging 52-55 microns. Both the trophozoite and cyst stages have 2 nuclei: a macronucleus and a micronucleus.
Treatment is typically tetracycline, which tends to be an effective medication for treating this infection. Other treatments may include metronidazole or iodoquinol.
Balantidium coli trophozoite-The only ciliated and largest parasite protozoan trophozoite found in the intestine. It measures 40 x 60 micrometers in size. It is the only ciliate that is pathogenic to humans. The trophozoite has 2 nuclei: a large kidney-bean-shaped macronucleus, and smaller round micronucleus
Cestodes: platyhelminthes: flatworms
Important Terminology and Facts:
Abopercular - terminal end
Anaphylaxis - anaphylactic shock; immune response in which histamine is released in response to allergens or proteins; it may result in death if not treated immediately
Anorexia - loss of appetite
Armed Scolex - scolex armed with a crown of hooks
Brood capsules - Echinococcus granulosus tapeworm daughter cyst structures within containing scolices, each of which can develop into an adult tapeworm within its definitive host
Cestoda - class of cestodes under phylum Platyhelminthes, which includes the tapeworms
Copepod - intermediate host in the fish tapeworm D. latum, which is a freshwater crustacean
Coracidium - the fish tapeworm D. latum eggs develop into this stage from the ciliated hexacanth embryo; this stage can then hatch in fresh water
Cysticercoid - this is the larval stage of some tapeworms; the scolex in enclosed in this structure, which is small and bladder-like, and may or may not contain any fluid
Cysticercus - this cyst is fluid-filled, has a thin wall, is also bladder-like, and surrounds a scolex, and some larvae develop into it
Embryophore - tapeworm eggshell
Hermaphroditic - both male and female simultaneously; contains both reproductive organs within the same structure; tapeworms contain both reproductive organs in each segment, or proglottid
Hexacanth Embryo - tapeworm larvae containing 6 hooklets
Hooks - structures on the scolex of some tapeworms, in addition to suckers, in 1-2 rows, which enhance the ability of the tapeworm to "hook" into and adhere to the mucosal tissues
Hydatid Cyst - larvae of E. granulosus form this structure in the intermediate host; contains a mixture of brood capsules, fluid, daughter cysts, and scolices of potential offspring tapeworms; can get pretty big
Hydatid Sand - granular material consisting of free hooklets, scolices, daughter cysts, found in the fluid of older hydatid cysts
Microvilli - finger-like structures that increase the surface area of small intestines for absorption of vitamins and minerals
Oncosphere - first-stage larvae of various cestodes; motile; contains 6 hooklets
Operculum - lid-like or cap-like structure at the end of some platyhelminthe eggs
Parenchyma - the internal organs of platyhelminthes are embedded in this tissue
Plerocercoid - larvael stage of the fish tapeworm; develops after a freshwater fish ingests the procercoid stage; immature scolex; infective stage to humans
Procercoid - larval stage of the fish tapeworm; develops from the coracidium in the body of a freshwater crustacean
Proglottid - tapeworm segment containing both male and female reproductive organs
Racemose - grape-like clusters consisting of branching, nodular terminations of the pork tapeworm larvae in the brain
Radial Striations - found around the edges of the pork and beef tapeworm eggs
Rostellum - anterior projection of the scolex of some tapeworms containing 1-2 rows of hooks, and may be retractable
Scolex - anterior end of a tapeworm; cephalic region; contains suckers and/or hooks for attachment to the mucosa
Sparganosis - human infection with procercoid stage of a cestode
Strobila - body of the tapeworm
Suckers - suction cups on the anterior cephalic end of a tapeworm for attachment to mucosa; may or may not also contain a row or rows of hooks
Tapeworms - a group of cestodes with bilateral symmetry, exhibiting flat, ribbon-like bodies with segments known as proglottids; they are acoelomates with no central body cavity
Tegument - body surface of the platyhelminthe; area of oxygen and nutrient absorption and waste excretion
Transport Host - vectors such as blood-sucking insects
Viscera - large organs inside any of the body cavities
Abopercular - terminal end
Anaphylaxis - anaphylactic shock; immune response in which histamine is released in response to allergens or proteins; it may result in death if not treated immediately
Anorexia - loss of appetite
Armed Scolex - scolex armed with a crown of hooks
Brood capsules - Echinococcus granulosus tapeworm daughter cyst structures within containing scolices, each of which can develop into an adult tapeworm within its definitive host
Cestoda - class of cestodes under phylum Platyhelminthes, which includes the tapeworms
Copepod - intermediate host in the fish tapeworm D. latum, which is a freshwater crustacean
Coracidium - the fish tapeworm D. latum eggs develop into this stage from the ciliated hexacanth embryo; this stage can then hatch in fresh water
Cysticercoid - this is the larval stage of some tapeworms; the scolex in enclosed in this structure, which is small and bladder-like, and may or may not contain any fluid
Cysticercus - this cyst is fluid-filled, has a thin wall, is also bladder-like, and surrounds a scolex, and some larvae develop into it
Embryophore - tapeworm eggshell
Hermaphroditic - both male and female simultaneously; contains both reproductive organs within the same structure; tapeworms contain both reproductive organs in each segment, or proglottid
Hexacanth Embryo - tapeworm larvae containing 6 hooklets
Hooks - structures on the scolex of some tapeworms, in addition to suckers, in 1-2 rows, which enhance the ability of the tapeworm to "hook" into and adhere to the mucosal tissues
Hydatid Cyst - larvae of E. granulosus form this structure in the intermediate host; contains a mixture of brood capsules, fluid, daughter cysts, and scolices of potential offspring tapeworms; can get pretty big
Hydatid Sand - granular material consisting of free hooklets, scolices, daughter cysts, found in the fluid of older hydatid cysts
Microvilli - finger-like structures that increase the surface area of small intestines for absorption of vitamins and minerals
Oncosphere - first-stage larvae of various cestodes; motile; contains 6 hooklets
Operculum - lid-like or cap-like structure at the end of some platyhelminthe eggs
Parenchyma - the internal organs of platyhelminthes are embedded in this tissue
Plerocercoid - larvael stage of the fish tapeworm; develops after a freshwater fish ingests the procercoid stage; immature scolex; infective stage to humans
Procercoid - larval stage of the fish tapeworm; develops from the coracidium in the body of a freshwater crustacean
Proglottid - tapeworm segment containing both male and female reproductive organs
Racemose - grape-like clusters consisting of branching, nodular terminations of the pork tapeworm larvae in the brain
Radial Striations - found around the edges of the pork and beef tapeworm eggs
Rostellum - anterior projection of the scolex of some tapeworms containing 1-2 rows of hooks, and may be retractable
Scolex - anterior end of a tapeworm; cephalic region; contains suckers and/or hooks for attachment to the mucosa
Sparganosis - human infection with procercoid stage of a cestode
Strobila - body of the tapeworm
Suckers - suction cups on the anterior cephalic end of a tapeworm for attachment to mucosa; may or may not also contain a row or rows of hooks
Tapeworms - a group of cestodes with bilateral symmetry, exhibiting flat, ribbon-like bodies with segments known as proglottids; they are acoelomates with no central body cavity
Tegument - body surface of the platyhelminthe; area of oxygen and nutrient absorption and waste excretion
Transport Host - vectors such as blood-sucking insects
Viscera - large organs inside any of the body cavities
capillaria philippinensis-fish tapeworm
Capillaria philippinensis is found in the Far East and the normal animal host is fish. Ingestion of raw, infected fish may lead to a fish tapeworm infection that can result in malabsorption syndrome, chronic, severe diarrhea, and death due to cardiac failure or other secondary infection. Adult worms may multiply in the intestines and lead to intestinal blockage. Perforation can lead to a deadly peritonitis.
chilomastix mesnili (Flagellated Protozoan)
a) Giardia sp. (cyst),
(b) Entamoeba hartmanni (cyst),
(c) Chilomastix mesnili (cyst),
(d) Entamoeba histolytica/dispar (cyst),
(e) Iodameoba butschlii (cyst),
(f) Endolimax nana (cyst),
(g) Balantidium coli (trophozoites),
(h) Blastocystis sp. (cyst),
(i) Entamoeba coli (cyst).
Scale bars: a–i = 5 μm.
Chilomastix mesnili trophozoites (7 x 20 micrometers) may inhabit the upper large intestine without causing any disease or symptoms and is normally considered non-pathogenic, but if it irritates the intestines, it can result in diarrhea. There is a single, large, prominent nucleus at the anterior, rounded end, whereas the posterior end is tapered with an angled projection. It contains 4 anterior flagella and has a distinct, longitudinal spiral groove. Trophozoites are motile and move in a spiral path. In the image above (c), one of the cysts can be seen.
Microscopic Appearance:
The cyst form is tiny and measures about 5 x 8 micrometers and can be found in the feces. It contains one, large nucleus and is a lemon-shaped cyst.
Trophozoite: pear-shaped, ranging from 10-15 microns by 3-4 microns with 3 anterior flagella and 1 located within the cytostome, a large round nucleus, some food vacuoles, a peripheral spiral groove, and a spiny projection at the posterior end
Cyst: lemon-shaped, 7-9 microns by 4-6 microns with a thickening at the anterior end
Microscopic Appearance:
The cyst form is tiny and measures about 5 x 8 micrometers and can be found in the feces. It contains one, large nucleus and is a lemon-shaped cyst.
Trophozoite: pear-shaped, ranging from 10-15 microns by 3-4 microns with 3 anterior flagella and 1 located within the cytostome, a large round nucleus, some food vacuoles, a peripheral spiral groove, and a spiny projection at the posterior end
Cyst: lemon-shaped, 7-9 microns by 4-6 microns with a thickening at the anterior end
Digenea: trematodes and flukes
Digenea Facts: Platyhelminthes: Flukes
- Digenea: comes from the Greek words "dis" meaning "double", and "Genas" meaning "race", referring to the alternation of generations between sexually-reproducing adult worms and asexually-reproducing larval stages
- This is the largest group of endoparasite metozoans:
- 150 families
- 2,700 genera
- >18,000 species, only 12 of which are infectious to humans
- Afflict >2 million individuals worldwide
- 150 families
- Digenea have multiple host life cycles
- Definitive host: a vertebrate
- First intermediate host: often a mollusc (snail)
- Additional hosts (2, 3, or even 4)
- Definitive host: a vertebrate
- Adults:
- Female lays an egg
- The miracidium develops inside the egg, hatches, swims out, and penetrates a mollusc or it eats it, then it hatches
- It forms a sporocyst
- It matures into a redia
- It matures into a cercaria larvae form, which is free-swimming
- The cercaria encysts on fish, crayfish, crab or vegetation, or directly penetrates the skin of humans
- It becomes a schistosomule
- It becomes a metacercariae
- It matures into an adult worm
- Worms are separate sexes, male and female, however, in the blood flukes, once they mate, they stay connected to each other
- The miracidium develops inside the egg, hatches, swims out, and penetrates a mollusc or it eats it, then it hatches
- Female lays an egg
- Live in fresh water and marine water and in estuaries
- The Japanese red algae Digenea simplex has been used as a natural, potent antihelminth for more than 1,000 years because it produces domoic and kainic acids
- Worm Structure:
- Tegument: body
- 2 Suckers: oral and ventral (acetabulum)
- Vermiform: unsegmented body
- Parenchyma: solid coelem; no body cavity
- Most, other than blood flukes, are hermaphroditic
- Internal fertilization
- Sperm is transferred via the cirrus to the Laurer's canal or genital aperture
- There are 2 to >100 testes, vasa efferontia, vas deferens, seminal vesicle, ejaculatory duct, cirrus, sac
- Ovary, oviduct, seminal receptacle, vitelline glands, yolk/eggshell production, ducts, ootype chamber, gland cells, Mehlis' gland, genital atrium, metraterm, sphincter, and spines
- Sperm is transferred via the cirrus to the Laurer's canal or genital aperture
- The body has a mouth, pharynx, a forked/blind/incomplete digestive tract with 2 tubular sacs (caeca) and some form a ring-shaped cyclocoel, an anus, uroproct, but it can also absorb/excrete through its tegument directly
- Paired ganglia serve as a rudimentary "brain" (cephalization), along with nerves, sensory receptors, and chemoreceptors
- Tegument: body
- Diet:
- Graze on lumen, food, bile, mucous, submucosa, blood
- Graze on lumen, food, bile, mucous, submucosa, blood
Important Terminology:
- Acetabulum: cup-shaped muscular suckers; located on the oral or ventral side of the fluke
- Cercariae: fluke life cycle stage that develops in a sporocyst or redia
- Final developmental stage in the intermediate snail host
- Body and a forked tail
- Free-swimming/living stage; motile
- Hundreds are produced from the asexual reproduction of each miracidium
- Blood Flukes: this stage is infectious to humans by penetrating the skin directly (Schistosomiasis)
- Final developmental stage in the intermediate snail host
- Class Digenea: Phylum Platyhelminthes; Subclass: Trematoda; Order: Flukes with dorsoventrally flattened, leaf-shaped bodies, nonsegmented, with two muscular suckers (oral and ventral) for attachment to mucosa; most are hermaphroditic
- Intestinal flukes
- Liver flukes
- Lung flukes
- Blood flukes
- Intestinal flukes
- Granulomas: cellular growth around a foreign body to wall it in and protect it from immune destruction, which often calcifies and hardens over time
- Metacercariae: fluke life cycle stage that develops when a cercariae has shed its tail and then secreted a protective wall around itself and encysts into a resting stage on a second intermediate host or on a water plant
- Infective stage to humans
- Infective stage to humans
- Microtriches: finger-like projections on the surface of the tegument of the trematode that aid in increasing the surface area for absorption of minerals and nutrients and excretion of waste products of metabolism
- Miracidium: The first-stage, ciliated form and free-swimming larvae of a trematode; hatches from the egg; penetrates a snail next to continue its life cycle
- Larval stage emerges from the egg in freshwater
- Enters the snail host
- Larvae goes through a few cycles of asexual multiplication
- Larval stage emerges from the egg in freshwater
- Operculum: lid-like structure at the terminal end of some trematode and other types of eggs that opens when the larvae hatches out; aids in identification of the egg
- Redia: The second-stage or third-stage of the larvae of a trematode; develops within a sporocyst in the snail host
- Elongated
- Sac-like
- Has a mouth and a gut
- Many develop in a single sporocyst
- Each one turns into many cercariae
- Elongated
- Schistosoma: blood fluke
- Elongated shape
- Separate sexes
- Found in mating pairs in the blood vessels of their definitive host
- Body of the male curves up along the lateral edges to form a long channel (gynecophoral canal) and wraps around the larger female worm, lying inside the channel
- Coexist as pairs during their adult lifespan in the blood vessels
- Body of the male curves up along the lateral edges to form a long channel (gynecophoral canal) and wraps around the larger female worm, lying inside the channel
- Elongated shape
- Schistosomule: immature schistosome in human tissues
- The next stage after the cercariae has lost its tail when it penetrates the skin
- The next stage after the cercariae has lost its tail when it penetrates the skin
- Spine: knob-like, lateral or terminal ends of Schistosoma eggs, which is a differentiating feature between them
- Sporocyst: Larval stage of a trematode that develops from a miracidium in the snail intermediate host
- Simple
- Saclike structure
- Contains germinal cells that bud off internally
- Germinal cells continue multiplying
- Many redia are produced in each sporocyst
- Simple
- Tegument: body skin
- Trematoda: Class: Trematodes
- Class of flatworms
- Phylum Platyhelminthes
- Subclass: Digenea
- Vary in length from several mm to several cm
- Simple digestive tract
- Oral cavity (opens in the center of the oral sucker)
- Intestinal tract (opens blindly in 1-2 sacs)
- No anal opening
- Waste products are regurgiated or excreted through the tegument directly via the microtriches
- Nutrients are ingested or absorbed directly through the tegument
- Oral cavity (opens in the center of the oral sucker)
- Class of flatworms
Clonorchis sinensis-oriental liver fluke
Phylum: platyhelminth
class: digenea
C. sinensis, Oriental or Chinese liver fluke, was discovered by Dr. James McConnell in 1874 at the Medical College Hospital in Calcutta, India. Chinese liver fluke is endemic to Asia, Russia, Korea, Vietnam and China.
Infection:
Humans become infected with C. sinensis by eating raw, undercooked, infected fish, which contain encysted metacercariae. Cats and dogs also serve as intermediate animal hosts or reservoirs, but the main intermediate hosts are snails.
Symptoms:
In the small intestine, the larvae excyst and travel to the bile ducts, maturing into adult worms in about 3-4 weeks. It causes obstructive liver damage, jaundice, extensive biliary fibrosis, and symptoms result in itching, irritation, and systemic toxemia, along with loss of appetite, diarrhea, abdominal pain, and eosinophilia (in about 5-40% of cases). In severe cases, pancreatitis, bile duct stones, cholangitis, and even liver cancer can occur. The disease caused by this worm is called clonorchiasis.
Adult worms are flat and spatulate and measure 10-25 mm x 3-5 mm. The worms are hemaphrodites, meaning they have both a single round ovary and two branched testes. Adult worms can survive 20-25 years!
Diagnosis:
Diagnosis is made by finding eggs in the feces or in biliary drainage aspirates. The small eggs are ovoid with a moderately thick shell and a seated operculum. Around the operculum is a thickened rim called "shoulders". The miracidium is developed. They are yellowish-brown in color. Eggs measure approximately 27-35 microns by 12-19 microns. At the abopercular end lies a small knob as seen in the images above. The knob is often difficult to see, however, and may even be absent. When passed in the stool, the eggs contain a miracidium. Embryonated eggs pass in the stool into water and are then ingested by an intermediate host, such as a snail or fish. Because eggs are passed intermittently, several stool samples should be examined.
Distribution:
Most infections outside the Orient occur in tropical areas such as in Hawaii and the West Coast. Infections may occur via ingestion of pickled fish that still have viable metacercariae.
Treatment:
Treatment consists of either praziquantel, albendazole, or biltricide, which affects the worm's sucker so that it can't attach. These are very strong medications with side effects. They pass through the liver and are excreted in the urine. Effects may affect the central nervous system, abdominal pain, diarrhea, nausea, vomiting, elevated liver enzymes, rash, itching, pain, fever, sweating, hypotension, and even cardiac arrhythmias, so treatments must be monitored closely.
Infection:
Humans become infected with C. sinensis by eating raw, undercooked, infected fish, which contain encysted metacercariae. Cats and dogs also serve as intermediate animal hosts or reservoirs, but the main intermediate hosts are snails.
Symptoms:
In the small intestine, the larvae excyst and travel to the bile ducts, maturing into adult worms in about 3-4 weeks. It causes obstructive liver damage, jaundice, extensive biliary fibrosis, and symptoms result in itching, irritation, and systemic toxemia, along with loss of appetite, diarrhea, abdominal pain, and eosinophilia (in about 5-40% of cases). In severe cases, pancreatitis, bile duct stones, cholangitis, and even liver cancer can occur. The disease caused by this worm is called clonorchiasis.
Adult worms are flat and spatulate and measure 10-25 mm x 3-5 mm. The worms are hemaphrodites, meaning they have both a single round ovary and two branched testes. Adult worms can survive 20-25 years!
Diagnosis:
Diagnosis is made by finding eggs in the feces or in biliary drainage aspirates. The small eggs are ovoid with a moderately thick shell and a seated operculum. Around the operculum is a thickened rim called "shoulders". The miracidium is developed. They are yellowish-brown in color. Eggs measure approximately 27-35 microns by 12-19 microns. At the abopercular end lies a small knob as seen in the images above. The knob is often difficult to see, however, and may even be absent. When passed in the stool, the eggs contain a miracidium. Embryonated eggs pass in the stool into water and are then ingested by an intermediate host, such as a snail or fish. Because eggs are passed intermittently, several stool samples should be examined.
Distribution:
Most infections outside the Orient occur in tropical areas such as in Hawaii and the West Coast. Infections may occur via ingestion of pickled fish that still have viable metacercariae.
Treatment:
Treatment consists of either praziquantel, albendazole, or biltricide, which affects the worm's sucker so that it can't attach. These are very strong medications with side effects. They pass through the liver and are excreted in the urine. Effects may affect the central nervous system, abdominal pain, diarrhea, nausea, vomiting, elevated liver enzymes, rash, itching, pain, fever, sweating, hypotension, and even cardiac arrhythmias, so treatments must be monitored closely.
opisthorchis veverrini and felineus
An egg of Opisthorchis viverrini, virtually identical to the egg of Clonorchis sinensis. These eggs tend to be a bit broader and the shoulders slightly less prominent. The knob at the opercular end may either be prominent, as seen in the image above, inconspicuous or even absent. Opisthorchis viverrini are also liver flukes that parasitize humans in Southeast Asia and Northern Europe.
This liver fluke causes the same symptoms as C. sinensis.
Dicrocoelium dendriticum-liver fluke
Dicrocoelium dendriticum is also another liver fluke that may infect sheep, cattle, herbivorous mammals, and even humans. It has a worldwide distribution, but most human cases occur in Asia, Europe and Africa. Intermediate hosts include snails and ants.
Diphyllobothrium latum-broad fish tapeworm
Infections with D. latum occur when humans ingest raw or undercooked fish that are parasitized with the infective larval stage (pleurocercoid) and are referred to as diphyllobothriasis. The scolex of this worm does not have hooks or cup-shaped suckers. The scolex is characterized by 2 grooved suckers (1 on each side of the scolex). The worm uses these suckers to attach itself to the small intestine mucosa. It can grow to 20 meters in length as seen in the image above! The mature segment is wider than the tail. It houses a rosette-shaped uterus with a pore through which eggs are excreted. It is the longest tapeworm of humans!
This parasite is found across the globe in fresh water. In the USA specifically, it has been found in FL, Alaska, and the Great Lakes region. Symptoms are usually vague, digestive disturbances, including abdominal pain, weight loss, weakness, malnutrition, anemia, hunger pains, epigastric fullness, nausea, and vomiting. Some patients are asymptomatic. Others may develop a macrocytic anemia (pernicious anemia) since the worm is competing for the same nutrients as its human host, including vitamin B12 and absorbs it quicker than its human host.
Cysts: yellow-brown, ranging from 45-65 microns with an inconspicuous operculum at one end and a small knob-like thickening at the other end.
This parasite is found across the globe in fresh water. In the USA specifically, it has been found in FL, Alaska, and the Great Lakes region. Symptoms are usually vague, digestive disturbances, including abdominal pain, weight loss, weakness, malnutrition, anemia, hunger pains, epigastric fullness, nausea, and vomiting. Some patients are asymptomatic. Others may develop a macrocytic anemia (pernicious anemia) since the worm is competing for the same nutrients as its human host, including vitamin B12 and absorbs it quicker than its human host.
Cysts: yellow-brown, ranging from 45-65 microns with an inconspicuous operculum at one end and a small knob-like thickening at the other end.
Dioctophyma renale-giant kidney worm
physaloptera spp
gongylonema spp
dipylidium caninum: the flea tapeworm
The flea tapeworm infects dogs, cats, and humans sometimes (mostly children) via affected fleas (intermediate hosts). Accidental ingestion of fleas or flea larvae of infected fleas results in infection with the flea tapeworm, represented by cucumber seed-like proglottids that also resemble grains of rice. The adult worm is able to reach 46 cm in length. Like a variety of other tapeworms, this tapeworm also has 4 suckers and 4 sets of hooks. Infected cats or dogs excrete about 3-4 segments a day.
Ecchinococcus granulosus-Hydatid cyst
This parasite causes Hydatid Disease, which is an extra-intestinal tapeworm infection. The main reservoir and host include dogs and sheep. Humans are accidental hosts, or end hosts in the life-cycle of E. granulosis and E. multilocularis. Infection occurs via ingestion of the eggs, which then hatch in the intestine and mature into larvae, penetrating through the intestinal wall. The larvae travel throughout the body, migrating to the liver, where the majority of them stay, though some may travel to the brain, kidneys, and lungs and infect them as well. The larvae each form a round, fluid-filled cyst called a "hydatid cyst". Hydatid cysts, as seen in the image above on the right, replicate via asexual budding. As a result, daughter cysts are formed inside the original cyst, where they grow up to 5-10 cm in size.
Symptoms result from the compression of the cyst on the organ surrounding it, whether that be the liver, brain, kidney(s) or lung(s), and the fluid inside the cysts may cause an allergic reaction in the host (in about 10%), which may be fatal. Treatment consists of surgical removal of the cysts or administration of albendazole for months to kill the cysts.
Symptoms result from the compression of the cyst on the organ surrounding it, whether that be the liver, brain, kidney(s) or lung(s), and the fluid inside the cysts may cause an allergic reaction in the host (in about 10%), which may be fatal. Treatment consists of surgical removal of the cysts or administration of albendazole for months to kill the cysts.
enterobius vermicularis-pinworms (nematode/roundworm)
Infection with this parasite occurs via ingestion of the eggs, and is referred to as enterobiasis. Once the eggs are ingested, pinworms mature in the ascending large intestine and in the cecum. The female worm travels to the perianal area during the night and lays eggs. About 4-6 hours later, they become infectious and cause severe perianal itching. If an infected person scratches the perianal area, they reinfect themselves or others and the disease is spread hand-to-mouth because the hands are now contaminated with microscopic eggs.
Diagnosis is made by placing Scotch tape or a pinworm paddle (Swube) firmly over the perianal area and viewing it microscopically. The sticky tape or paddle picks up the eggs, which can then be viewed under the microscope as seen in the images above. Sometimes at night, if a flashlight is briefly flashed on the perianal area, the female worm may be visibly seen with the unaided eye, crawling across the perianal area. The Swube sometimes captures the female worm along with her eggs.There is no tissue invasion, so eosinophilia will not be observed with this condition. Treatment includes avoidance of scratching, changing the bed linens each day and disinfecting them with hot water, and administration of mebendazole or pyrantel pamoate.
Worms:
The worms mature in the anterior area of the colon. Female worms measure 8-13 mm. Male worms measure 2-5 mm. Inside, they have a bulbar esophagus and projections that resemble fins (cephalic alae) on their anterior end. The male has a sharply curved tail (caudal curve) and a little posterior copulatory spicule. The female tail is long, straight and sharply pointed. When the female uterus is gravid (pregnant with eggs), it leaves the colon during the nocturnal hours and travels to the perianal area or to the appendix and she deposits her eggs and then dies. Pinworm disease is the result of an allergic reaction to those deposits of eggs along with the secreted chemicals from the gravid female. This results in severe rectal pruritis (itching).
Eggs:
The eggs resemble jelly beans, being flattened on one side of the shell. The eggs can be recovered from the perianal folds with scotch tape or a pinworm paddle by applying the paddle or tape sticky-side-down onto the skin surfaces, then placing the tape or pinworm paddle on a microscope slide for viewing under low-power and low-light since the eggs are transparent. The eggs measure 55 micrometers x 25 micrometers. The shell is thick and hyaline or transparent, without color, and the folded larva can be seen inside. Inside the host, these eggs are infective for a few hours after they've been released, resulting in an immune reaction and itching. If the perianal region is scrached, the eggs can then be transferred by hand-to-mouth transmission, where they hatch shortly after ingestion, growing into mature worms in about 2 weeks. Fomites that may carry the eggs include bedding, PJ's, mattresses, and dust. Ingestion or even inhalation of eggs that have become airborne can result in infection. It is common in the USA and it is easily spread. Families can become infected.
Symptoms:
Many cases are actually asymptomatic, but sometimes, severe symptoms can occur if there is heavy worm infestation and an intestinal blockage. In this case, intestinal lesions may form (little ulcers), resulting in inflammation. About 50% of patients infected complain of abdominal pain.
When the gravid female migrates out of the intestines at night to come out of the anus and lay her eggs on the perianal region, this causes intense itching and irritation. This results from the hypersensitivity reaction of the immune system. Eggs get on the fingers and underneath the nails during scratching, are ingested by hand-to-mouth transmission, resulting in autoreinfection. Some people also experience mild nausea and even vomiting, loss of appetite, loss of sleep due to pruritis and enuresia (teeth-grinding), irritability, and females can also experience vulvar itching and irritation if migrating worms enter the vaginal area. This causes peritoneal or pelvic granulomas and can cause secondary bacterial infection or superinfection.
If the eggs hatch on the perianal and rectal area, they can quickly mature into larvae and travel back into the intestines. The female worm has a long, pointed tail, and is larger than the male. She also has fins on the sides of her mouth known as cephalic alae. She establishes herself in the colon (cecum and ileum). From the time of ingestion to the time of oviposition is about 1-2 months. Her lifespan is about 2 months and she grows to about 8-13 mm in length. The larvae that hatch from the eggs are infections in just 4-6 hours and may be ingested or inhaled if they become airborne.
Treatment:
Symptomatic infections are treated with 100 mg of mebendazole or pyrantel pamoate 1x per day, or 400 mg of albendazole, which is 1 pill, but it is repeated again in 2 weeks. The whole household should be treated.
Distrubution:
This nematode is found worldwide, but it is the most common helminth infection in the USA. It is most common among children and humans are the only known host, though eggs are frequently found in the soil. The gravid female can lay up to 15,000 eggs, which become infective within just a short 4 hours of release. They remain infective for a few days, which is why it is so important to treat the host, their household, pets, and the environment, in order to break this cycle.
Diagnosis is made by placing Scotch tape or a pinworm paddle (Swube) firmly over the perianal area and viewing it microscopically. The sticky tape or paddle picks up the eggs, which can then be viewed under the microscope as seen in the images above. Sometimes at night, if a flashlight is briefly flashed on the perianal area, the female worm may be visibly seen with the unaided eye, crawling across the perianal area. The Swube sometimes captures the female worm along with her eggs.There is no tissue invasion, so eosinophilia will not be observed with this condition. Treatment includes avoidance of scratching, changing the bed linens each day and disinfecting them with hot water, and administration of mebendazole or pyrantel pamoate.
Worms:
The worms mature in the anterior area of the colon. Female worms measure 8-13 mm. Male worms measure 2-5 mm. Inside, they have a bulbar esophagus and projections that resemble fins (cephalic alae) on their anterior end. The male has a sharply curved tail (caudal curve) and a little posterior copulatory spicule. The female tail is long, straight and sharply pointed. When the female uterus is gravid (pregnant with eggs), it leaves the colon during the nocturnal hours and travels to the perianal area or to the appendix and she deposits her eggs and then dies. Pinworm disease is the result of an allergic reaction to those deposits of eggs along with the secreted chemicals from the gravid female. This results in severe rectal pruritis (itching).
Eggs:
The eggs resemble jelly beans, being flattened on one side of the shell. The eggs can be recovered from the perianal folds with scotch tape or a pinworm paddle by applying the paddle or tape sticky-side-down onto the skin surfaces, then placing the tape or pinworm paddle on a microscope slide for viewing under low-power and low-light since the eggs are transparent. The eggs measure 55 micrometers x 25 micrometers. The shell is thick and hyaline or transparent, without color, and the folded larva can be seen inside. Inside the host, these eggs are infective for a few hours after they've been released, resulting in an immune reaction and itching. If the perianal region is scrached, the eggs can then be transferred by hand-to-mouth transmission, where they hatch shortly after ingestion, growing into mature worms in about 2 weeks. Fomites that may carry the eggs include bedding, PJ's, mattresses, and dust. Ingestion or even inhalation of eggs that have become airborne can result in infection. It is common in the USA and it is easily spread. Families can become infected.
Symptoms:
Many cases are actually asymptomatic, but sometimes, severe symptoms can occur if there is heavy worm infestation and an intestinal blockage. In this case, intestinal lesions may form (little ulcers), resulting in inflammation. About 50% of patients infected complain of abdominal pain.
When the gravid female migrates out of the intestines at night to come out of the anus and lay her eggs on the perianal region, this causes intense itching and irritation. This results from the hypersensitivity reaction of the immune system. Eggs get on the fingers and underneath the nails during scratching, are ingested by hand-to-mouth transmission, resulting in autoreinfection. Some people also experience mild nausea and even vomiting, loss of appetite, loss of sleep due to pruritis and enuresia (teeth-grinding), irritability, and females can also experience vulvar itching and irritation if migrating worms enter the vaginal area. This causes peritoneal or pelvic granulomas and can cause secondary bacterial infection or superinfection.
If the eggs hatch on the perianal and rectal area, they can quickly mature into larvae and travel back into the intestines. The female worm has a long, pointed tail, and is larger than the male. She also has fins on the sides of her mouth known as cephalic alae. She establishes herself in the colon (cecum and ileum). From the time of ingestion to the time of oviposition is about 1-2 months. Her lifespan is about 2 months and she grows to about 8-13 mm in length. The larvae that hatch from the eggs are infections in just 4-6 hours and may be ingested or inhaled if they become airborne.
Treatment:
Symptomatic infections are treated with 100 mg of mebendazole or pyrantel pamoate 1x per day, or 400 mg of albendazole, which is 1 pill, but it is repeated again in 2 weeks. The whole household should be treated.
Distrubution:
This nematode is found worldwide, but it is the most common helminth infection in the USA. It is most common among children and humans are the only known host, though eggs are frequently found in the soil. The gravid female can lay up to 15,000 eggs, which become infective within just a short 4 hours of release. They remain infective for a few days, which is why it is so important to treat the host, their household, pets, and the environment, in order to break this cycle.
fasciolopsis buski-intestinal fluke (fascioliasis)
Fasciolopsis buski is a large intestinal fluke. In fact, it is the largest intestinal fluke of humans. It is found in the Far East, including China, Vietnam, Thailand, Indonesida, Malaysia, India, the Philippines, and Asia. The adult worms hatch (excyst) from eggs in the duodenum, where they live in the small intestine and attach to the intestinal wall. It takes about 3 months for the larval stage to develop into an adult. Their lifespan is about a year. The infective stage to humans is the metacercariae, which have encysted on raw aquatic vegetation.
This organism has a sheep or pig as a definitive host. Humans are accidental hosts, so infection in humans is zoonotic disease.
Symptoms and Infection:
Symptoms include fever, diarrhea, edema, ascites fluid, pain, nausea, eosinophilia, and malabsorption with anemia. Heavy infection can be deadly. Complications may include ulceration of the bowel mucosa, hypersecretion and hemorrhage. Disease is called fasciolopsiasis.
Diagnosis:
Diagnosis consists of finding the large eggs in the feces.
Treatment:
Treatment includes the prescription of niclosamide or praziquantel.
This organism has a sheep or pig as a definitive host. Humans are accidental hosts, so infection in humans is zoonotic disease.
Symptoms and Infection:
Symptoms include fever, diarrhea, edema, ascites fluid, pain, nausea, eosinophilia, and malabsorption with anemia. Heavy infection can be deadly. Complications may include ulceration of the bowel mucosa, hypersecretion and hemorrhage. Disease is called fasciolopsiasis.
Diagnosis:
Diagnosis consists of finding the large eggs in the feces.
Treatment:
Treatment includes the prescription of niclosamide or praziquantel.
Fasciola hepatica-liver fluke
Fasciola hepatica is known as the sheep liver fluke or common liver fluke. The intermediate hosts for this organism are sheep and cattle. Humans are accidental hosts, resulting in zoonotic disease.
Distribution:
It is found in all continents, across more than 70 countries. In the USA, the cases are rare, and have typically only occurred in immigrants.
Symptoms:
Humans become infected by ingesting encysted metacercariae on raw aquatic vegetation. The adult worm migrates through the peritoneal cavity and liver parynchema, where it lives in the biliary ducts. This blockage can result in hepatic liver disease, jaundice, gallstones, and is even linked to liver cancer. Symptoms result from the mechanical irritation due to the larval migration and production of toxic worm metabolites. As the larvae migrate, they cause local irritation, fever, enlarged liver, tenderness and pain, and eosinophilia. Worms blocking the bile ducts also cause portal cirrhosis, diarrhea and anemia. Itching, hives, and a cough may also occur due to the immune system allergic response and release of histamines.
Treatment:
Treatment for infection may either be Triclabendazole (preferred) or bithionol.
Distribution:
It is found in all continents, across more than 70 countries. In the USA, the cases are rare, and have typically only occurred in immigrants.
Symptoms:
Humans become infected by ingesting encysted metacercariae on raw aquatic vegetation. The adult worm migrates through the peritoneal cavity and liver parynchema, where it lives in the biliary ducts. This blockage can result in hepatic liver disease, jaundice, gallstones, and is even linked to liver cancer. Symptoms result from the mechanical irritation due to the larval migration and production of toxic worm metabolites. As the larvae migrate, they cause local irritation, fever, enlarged liver, tenderness and pain, and eosinophilia. Worms blocking the bile ducts also cause portal cirrhosis, diarrhea and anemia. Itching, hives, and a cough may also occur due to the immune system allergic response and release of histamines.
Treatment:
Treatment for infection may either be Triclabendazole (preferred) or bithionol.
The life cycles of f. buski and f. hepatica:
- Adult Fluke
- F. buski: in small intestine
- F. hepatic: in biliary ducts of liver
- F. buski: in small intestine
- Diagnostic Stage:
- Eggs in feces
- Eggs in feces
- Miracidia hatch from eggs in water and develop
- Miracidia enter snail intermediate host
- Miracidia enter snail intermediate host
- Sporocyst
- Redia I
- Redia II
- Cercariae leave snail as free-swimmers
- Infective Stage:
- Cercariae encyst on water plants as metacercariae (resting stage)
- Human ingests the metacercariae from raw aquatic plants
- Metacercariaea excyst in the small intestinal tract (duodenum)
- Cercariae encyst on water plants as metacercariae (resting stage)
- F. hepatic migrates to liver parynchema into biliary ducts
heterophyes heterophyes-Heterophyiasis; intestinal fluke
Heterophyes heterophyes is the causative agent of heterophyiasis. It was discovered by Max Bilharz in 1851 during an autopsy of an Egyptian mummy.
It occurs in the Far East, Near East, and areas of Africa. These are primarily parasites of cats and dogs and fish-eating mammals. Human infection is accidental and zoonotic.
Infection:
Infection occurs if humans ingest the metacercariae on raw or undercooked contaminated fish (freshwater or brackish water). Metacercariae excyst in the mucosa of the small intestine where the larvae mature into adult worms and reside in the small intestine, latching on with their 3 suckers (oral, ventral, genital).
Diagnosis:
Diagnosis is made through the recovery and identification of embryonated eggs in the feces with fully developed miracidium, or in the duodenal drainage aspirate. The egg looks very similar to C. sinensis. There is a tiny operculum at one end, a small terminal knob at the other end, developing miracidium, and shoulders under the operculum that are less-developed than that of C. sinensis. The egg is about 30 x 16 micrometers. Eggs may migrate into tissues, resulting in protective granulomas and tissue diseases. The worm is unique because it has an extra sucker near the genital pore.
Symptoms:
Infections may be asymptomatic unless there is a heavy infection. Heavy infections may cause chronic mucoid diarrhea with abdominal pain. Heavy worm burden may cause migration of worms to the heart or brain, granuloma formation, and myocarditis with possible valve damage.
Treatment:
Treatment is praziquantel, which has some severe side effects (see C. sinensis).
Life Cycle:
It occurs in the Far East, Near East, and areas of Africa. These are primarily parasites of cats and dogs and fish-eating mammals. Human infection is accidental and zoonotic.
Infection:
Infection occurs if humans ingest the metacercariae on raw or undercooked contaminated fish (freshwater or brackish water). Metacercariae excyst in the mucosa of the small intestine where the larvae mature into adult worms and reside in the small intestine, latching on with their 3 suckers (oral, ventral, genital).
Diagnosis:
Diagnosis is made through the recovery and identification of embryonated eggs in the feces with fully developed miracidium, or in the duodenal drainage aspirate. The egg looks very similar to C. sinensis. There is a tiny operculum at one end, a small terminal knob at the other end, developing miracidium, and shoulders under the operculum that are less-developed than that of C. sinensis. The egg is about 30 x 16 micrometers. Eggs may migrate into tissues, resulting in protective granulomas and tissue diseases. The worm is unique because it has an extra sucker near the genital pore.
Symptoms:
Infections may be asymptomatic unless there is a heavy infection. Heavy infections may cause chronic mucoid diarrhea with abdominal pain. Heavy worm burden may cause migration of worms to the heart or brain, granuloma formation, and myocarditis with possible valve damage.
Treatment:
Treatment is praziquantel, which has some severe side effects (see C. sinensis).
Life Cycle:
- In fresh or brackish water, miracidia hatch and enter a snail (Cerithidia pironella), the first intermediate host.
- Miracidia develop into sporocysts
- Sporocysts develop into redia I
- Redia II
- Redia II develop into cercariae, leaving the snail as free-swimming/living
- Cercariae encyst on the outside of fish as metacercariae, the infective stage for mammals
hymenolepsis diminuta: Rat tapeworm
necator americanus-new world hookworm
The adult worm of the new world hookworm is identified by its unique buccal capsule containing a pair of semilunar cutting plates in its upper mouth and another pair of smaller plates on the lower mouth.
Hookworm eggs have a thin, hyaline shell and a clear area around the embryo. Eggs are recovered in feces, where they mature in 1-2 days. Once they hatch, the rhabditiform larvae are freed and mature in the soil into infective filariform larvae. The embryo is underdeveloped and contain 4-8 blastomeres in immature eggs. In mature eggs, however, developing rhabdiform larvae may be observed internally. Eggs measure 30 micrometers by 50 micrometers.
Human infection occurs when the filariform larvae (infective stage) in the soil penetrate the skin of the feet, especially between the toes. The larvae are carried via the lymphatic system and bloodstream throughout the body to the lungs and esophagus, where they are then swallowed and carried to the intestine, where they mature within about 2 weeks.
Hookworm eggs have a thin, hyaline shell and a clear area around the embryo. Eggs are recovered in feces, where they mature in 1-2 days. Once they hatch, the rhabditiform larvae are freed and mature in the soil into infective filariform larvae. The embryo is underdeveloped and contain 4-8 blastomeres in immature eggs. In mature eggs, however, developing rhabdiform larvae may be observed internally. Eggs measure 30 micrometers by 50 micrometers.
Human infection occurs when the filariform larvae (infective stage) in the soil penetrate the skin of the feet, especially between the toes. The larvae are carried via the lymphatic system and bloodstream throughout the body to the lungs and esophagus, where they are then swallowed and carried to the intestine, where they mature within about 2 weeks.
paragonimus westermani-paragonimiasis; lung fluke
Paragonimus westermani, oriental lung fluke, was discovered in 1878 by Coenraad Kerbert. It was named after Pieter Westerman, who was a zookeeper who noted it in a Bengal tiger in a zoo in Amsterdam. The disease it causes is known as paragonimiasis.
Infection:
There are at least 8 different species of Paragonimus that are infectious to humans. P. kellicotti is found in the USA (Midwest and Southern USA). P. mexicanus is found in Central and South America. The method of infection to humans is when humans accidentally ingest metacercariae from undercooked crabs or crayfish, the second intermediate hosts. In Tawaiin fresh markets, rows of raw crabs are strung together and pickled in wine or vinegar with salt, but this does not destroy the metacercariae.
Adult worms encyst in the lungs, often in pairs, after 6-10 weeks. From there, the eggs leave in sputum or feces, where they can be identified in fecal or sputum samples.
Diagnosis:
The diagnosis involves the recovery and identification of eggs in bloody sputum, often called rusty filings, due to the iron in blood, or in the feces, which can occur if the eggs are coughed up and then swallowed. In addition to laboratory tests, a chest X-ray will often point to patchy infiltrates with modular cystic shadows (calcifications). It can resemble tuberculosis at first.
The eggs are large (85 x 55 micrometers) with undeveloped miracidium. There is a large operculum with an opercular rim (shoulders) underneath. The shell is smooth, thin, and dark golden-brown, with a terminal shell thickening.
Symptoms:
Symptoms may include chronic chest pain, a cough with blood-tinged sputum (rust-colored), lung infiltration, nodules, and even abscesses. Inside the fibrous cysts, adult worms are found. Female adult worms lay eggs, which pass through the cysts, rupture, enter the bronchioles, and cause asthma-like symptoms with a cough. Chronic bronchitis and lung fibrosis may also occur. Sometimes the scarring from lung fibrosis is irreversible. Symptoms begin about 2-15 days after the worm is in the lung.
In rare cases, immature flukes may migrate to other tissues, including the brain, liver and skin, reasulting in symptoms related to infection, including meningitis (cerebral paraogonimiasis).
Distribution:
This parasite is most commonly found in the Far East. Other places it has been found are in Africa and South America.
Treatment:
Treatment consists of one of the following: praziquantel, bithionol, triclabendazole.
Life Cycle:
Infection:
There are at least 8 different species of Paragonimus that are infectious to humans. P. kellicotti is found in the USA (Midwest and Southern USA). P. mexicanus is found in Central and South America. The method of infection to humans is when humans accidentally ingest metacercariae from undercooked crabs or crayfish, the second intermediate hosts. In Tawaiin fresh markets, rows of raw crabs are strung together and pickled in wine or vinegar with salt, but this does not destroy the metacercariae.
Adult worms encyst in the lungs, often in pairs, after 6-10 weeks. From there, the eggs leave in sputum or feces, where they can be identified in fecal or sputum samples.
Diagnosis:
The diagnosis involves the recovery and identification of eggs in bloody sputum, often called rusty filings, due to the iron in blood, or in the feces, which can occur if the eggs are coughed up and then swallowed. In addition to laboratory tests, a chest X-ray will often point to patchy infiltrates with modular cystic shadows (calcifications). It can resemble tuberculosis at first.
The eggs are large (85 x 55 micrometers) with undeveloped miracidium. There is a large operculum with an opercular rim (shoulders) underneath. The shell is smooth, thin, and dark golden-brown, with a terminal shell thickening.
Symptoms:
Symptoms may include chronic chest pain, a cough with blood-tinged sputum (rust-colored), lung infiltration, nodules, and even abscesses. Inside the fibrous cysts, adult worms are found. Female adult worms lay eggs, which pass through the cysts, rupture, enter the bronchioles, and cause asthma-like symptoms with a cough. Chronic bronchitis and lung fibrosis may also occur. Sometimes the scarring from lung fibrosis is irreversible. Symptoms begin about 2-15 days after the worm is in the lung.
In rare cases, immature flukes may migrate to other tissues, including the brain, liver and skin, reasulting in symptoms related to infection, including meningitis (cerebral paraogonimiasis).
Distribution:
This parasite is most commonly found in the Far East. Other places it has been found are in Africa and South America.
Treatment:
Treatment consists of one of the following: praziquantel, bithionol, triclabendazole.
Life Cycle:
- In freshwater, miracidia hatch
- Miracidia enter the snail, the first intermediate host
- The miracidia becomes sporocysts
- Sporocysts become redia I
- Redia I become redia II
- After about 3-5 months, redia II become cercariae, and leave the snail as free-swimmers
- Cercariae penetrate freshwater crabs or crayfish after about 2 months, encysting as metacercariae
- Mammals inadvertently ingest the metacercariae from undercooked contaminated crabs or crayfish
schistosoma-schistosomiasis (blood fluke and bladder worm)
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Next to malaria, Schistosomiasis ranks second as a cause of major worldwide morbidity and mortality and is common in snail breeding areas. In fact, more than 2 million people worldwide are infected annually over 77 countries, and there are about 800,000 reported deaths each year. It is spreading.
S. haematobium has a clinical link to bladder carcinoma (cancer). Infections with free-living forked cercariae may result in allergic dermatitis called "swimmer's itch" in freshwater swimming areas.
Infection:
Infection occurs when free-swimming fork-tailed cercariae penetrate the skin, shedding the tail, and becoming schistosomules. It takes about 10 minutes to 30 minutes for the 0.2 x 1.0 mm cercariae to penetrate the skin and get into the bloodstream. Schistosomiasis may be acute or chronic and affect children and adults alike in endemic areas.
The initial reaction is an allergic dermatitis from cercariae penetration of the skin, known as "swimmer's itch", and produces a widespread itchy rash. The acute phase begins with typhoid fever-like symptoms, fever, cough, muscle pain, fatigue, and abdominal pain due to enlarged liver and spleen.
This can progress to cirrhosis of the liver, jaundice, blood diarrhea, bowel obstruction, high blood pressure, and toxic reactions of the body and skin due to the granulomas produced around the eggs. Eosinophilia is very common.
Chronic cases may be asymptomatic in endemic areas. Schistosomes feast on red blood cells, producing a brown hematin pigment, which may be present in phagocytic cells and even in the urine if the bladder is infected. Nephrotic syndrome with kidney failure may occur with S. haematobium and S. mansoni. This results in kidney damage, proteinuria, decreased albumin levels, increased lipids, edema, weight gain, fatigue, foamy urine, and bladder pain.
Treatment:
The treatment is praziquantel and/or niclosamide ointment on the skin.
Diagnosis:
Diagnosis is made by recovery and identification of eggs in feces or rectal biopsies or urine. It is important to find out the recent travel history and the clinical signs and symptoms.
Other Facts:
Types:
S. haematobium has a clinical link to bladder carcinoma (cancer). Infections with free-living forked cercariae may result in allergic dermatitis called "swimmer's itch" in freshwater swimming areas.
Infection:
Infection occurs when free-swimming fork-tailed cercariae penetrate the skin, shedding the tail, and becoming schistosomules. It takes about 10 minutes to 30 minutes for the 0.2 x 1.0 mm cercariae to penetrate the skin and get into the bloodstream. Schistosomiasis may be acute or chronic and affect children and adults alike in endemic areas.
The initial reaction is an allergic dermatitis from cercariae penetration of the skin, known as "swimmer's itch", and produces a widespread itchy rash. The acute phase begins with typhoid fever-like symptoms, fever, cough, muscle pain, fatigue, and abdominal pain due to enlarged liver and spleen.
This can progress to cirrhosis of the liver, jaundice, blood diarrhea, bowel obstruction, high blood pressure, and toxic reactions of the body and skin due to the granulomas produced around the eggs. Eosinophilia is very common.
Chronic cases may be asymptomatic in endemic areas. Schistosomes feast on red blood cells, producing a brown hematin pigment, which may be present in phagocytic cells and even in the urine if the bladder is infected. Nephrotic syndrome with kidney failure may occur with S. haematobium and S. mansoni. This results in kidney damage, proteinuria, decreased albumin levels, increased lipids, edema, weight gain, fatigue, foamy urine, and bladder pain.
Treatment:
The treatment is praziquantel and/or niclosamide ointment on the skin.
Diagnosis:
Diagnosis is made by recovery and identification of eggs in feces or rectal biopsies or urine. It is important to find out the recent travel history and the clinical signs and symptoms.
Other Facts:
- Adult males are shorter and thicker than females, with a long groove on one side they clasp around the female, where they remain as mating pairs for their 3-5 year average lifespan. Rarely, worms have been known to live up to 40 years!
- They may have originated as parasites of hippos
- They likely evolved in Gondwana
- They are similar to elephant schistosomes
- They were named by Theodor Max Bilharz, German pathologist, in Egypt in 1851, who first discovered the eggs when studying an Egyptian mummy.
- The disease was nicknamed "bilharziasis" or "swamp fever".
- The disease was nicknamed "bilharziasis" or "swamp fever".
Types:
- Schistosoma mansoni
- Eggs in feces or rectal biopsy
- Eggs 180 x 80 micrometers with a large, lateral spine and developed miracidium
- Adult female lays up to 300 eggs per day
- Adult pairs in blood vessels in liver sinuses and veins around the intestinal tract
- Found in Africa and South and Central America and parts of the Caribbean and large urban areas, including New York and Chicago in the USA due to immigration
- Coinfection with Salmonella spp is common
- Eggs in feces or rectal biopsy
- Schistosoma japonicum
- Eggs in feces or rectal biopsy
- Eggs 80 x 60 micrometers with a tiny lateral spine that is often difficult to see and developed miracidium
- Adult female lays up to 3,000 eggs per day
- Adult pairs in blood vessels in liver sinuses and veins around the intestinal tract
- Found in the Far East
- Coinfection with Salmonella spp is common
- Infects many different types of mammals
- This one is pretty much eradicated
- Eggs in feces or rectal biopsy
- Schistosoma intercalatum
- Found in Africa
- Found in Africa
- Schistosoma mekongi
- Found in the Mekong Basin
- Found in the Mekong Basin
- Schistosoma haematobium
- Eggs in concentrated urine
- Eggs are 160 x 80 micrometers with a large terminal spine (middle/end) and developed miracidium
- Adults paired in veins around the urinary bladder or the venules of the pelvis or mesentery
- Found in Africa and the Middle East
- Linked to bladder carcinoma
- Eggs in concentrated urine
- Avian Cercariae:
- Allergic dermatitis (swimmer's itch) in freshwater at swimming resorts in the USA
- Allergic dermatitis (swimmer's itch) in freshwater at swimming resorts in the USA
Strongyloides stercoralis-threadworm
taenia saginatum and taenia solium-beef tapeworm; pork tapeworm
trichinella spiralis-trichinosis
trichuris trichiura-whipworm
Trichuris trichiura (whipworm) can be identified by its unique "football-shaped" eggs and/or the adult worm with its whip-like tail. The adult female worm measures 35-50 mm. The anterior end is so thin and slender like a thread or "whip", and the posterior end is wider. The female and male worms can be differentiated by the female's club-shaped, straight posterior body and the male's 360 degree coiled posterior body consisting of 2 copulatory spicules. Since they each contain a spearlike projection, they use this to attach to the intestinal mucosa in the cecum and proximal colon. It thrives in moist, warm habitats and is found in the USA and across the globe. If the infection is light, there may be no symptoms at all, but if the parasitemia is heavy, it may result in diarrhea, enteritis, and rectal prolapse in severe cases.
Diganosis is made by recovery of eggs in the feces. Eggs measure 20 micrometers by 50 micrometers. There are hyaline "plugs" at each end of the egg. The shell is thick, and the embryo is underdeveloped. The complete cycle from ingestion of the egg until the egg is excreted in the feces is about 90 days!
Diganosis is made by recovery of eggs in the feces. Eggs measure 20 micrometers by 50 micrometers. There are hyaline "plugs" at each end of the egg. The shell is thick, and the embryo is underdeveloped. The complete cycle from ingestion of the egg until the egg is excreted in the feces is about 90 days!
trichostrongylus
the amoebae
Important Terminology:
- Acanthaemoeba keratitis: serious eye infection of the cornea by contamined contact lens solution or tap water containing Acanthamoeba spp.; rarely progresses to CNS infection of the brain (see Granulomatous Amebic Encephalitis)
- Amebiasis: disease caused by pathogenic amoebae
- Amoebida: order of ameboid protozoa
- Mitochondria - energy powerhouse (produces ATP)
- Lacks a flagellate phase
- Most are free-living
- Some are parasites of animals or humans
- Vary in size
- Vary in speed of motility
- Vary in cytoplasmic inclusions
- Vary in the size and structure of the nucleus
- Most are nonpathogenic but need to be correctly identified for proper treatment or to avoid unnecessary treatment
- Arthropod: insect carrier or vector
- Hard, segmented exoskeleton made of chitin
- Paired, jointed legs
- Binary Fission: asexual reproduction by dividing
- Chromatin:basophilic nuclear DNA
- Chromatoid Bars/Bodies: rod-shaped or cigar-shaped structures of condensed RNA inside the cytoplasm of some amoeba cysts that aid in their identification
- Cilia: hairlike structures all over the surface of some protozoans that serve as sensory functions or aid in locomotion and motility through fluids
- Cutaneous: skin
- Cyst: resting state, nonfeeding, nonmotile, protected by a resistant cyst wall that is thick and protective; very infective and transmissible to another host
- Infective stage for humans
- Found in fecally contaminated food or water
- Excyst in the lower intestine when swallowed and begin to multiply as feeding, active, motile trophozoites (trophs)
- Dysentery: bloody diarrhea that may or may not also have mucous; often called "amebic dysentery"
- E. histolytica is the main cause of this and the major pathogen in the group of intestinal amoebae in humans
- It can also occur in dogs, cats, rates, other primates
- Eccentric: off-centered (not centrally located), as in the nucleus, and/or the karyosome/endosome
- Ectoplasm: gel-like cytoplasm inside the cell in which organelles are suspended
- Encyst: to form a resting cyst stage
- Endoplasm: fluid inner cytoplasmic material in the cell
- Endosome: small mass of chromatin inside the nucleus, which is like the nucleolus of animal cells; it is also called the karyosome
- Excystation: cyst transforms into a motile, active, feeding trophozoite form after the cyst form is ingested by the host
- Fomites: inanimate objects that transmit disease and can harbor organisms (towels, bedding, linens, clothing, combs/brushes, toothbrushes, utensils, keyboards, phones, doorknobs, pens/pencils, surfaces, etc...)
- Granulomatous Amebic Encphalitis: infection of those who are immunocompromised, whose onset is slow, resulting in chronic granulomatous lesions in brain tissue, which may contain cysts and trophozoites, after entry through respiratory tract, broken skin or mucous membranes, or through direct invasion of the eye
- Karyosome: small mass of chromatin inside the nucleus, which is equivalent to the nucleolus of animal cells; it is also called the endosome
- Nucleus: central region of the cell surrounded by nuclear chromatin and membrane, which houses the DNA
- Structure is different for each species of amoeba, which aid in identification and differentiation
- Each type has varying numbers of nuclei
- Iodine wet mount and a permanent Trichrome stain are useful in identifying the cysts
- Primary Amebic Meningoencephalitis: fatal form of meningoencephalitis caused by the amoeba Naegleria fowleri infecting brain and spinal tissue
- Protozoa: Subkingdom that consists of unicellular eukaryotes
- Pseudopod: "false feet"; protoplasmic extensions of the trophozoite cell membranes that enables them to move and engulf food by phagocytosis
- Sarcodina: Subphylum containing amoebae that move by pseudopodia or "false feet"
- Trophozoite: the active, motile, feeding stage of protozoa in which they multiply and feed within the host
- Only live in liquid stool for about 30 minutes after evacuation
- Most commonly lives in the lower GI tract
- Vacuole: storage vesicle for glycogen, iron, pigments, and other foods
acanthamoeba-meningoencephalitis; eye damage; blindness
Acanthamoeba spp is a free-living amoeba that is able to cause eye infections (keratitis) and even blindness. It is crucial for contact-wearers to properly wash and disinfect their contact lenses using proper sterile lens solutions rather than using tap water to clean lenses, as tap water is often contaminated with the amoeba.
CSF, brain tissue, or corneal scrapings are the specimen of choice for recovery of this organism. Calcofluor white may be used to stain the cysts present in corneal scrapings. The amoeba is able to invade the CNS from the lower respiratory tract or the skin, particularly in immunocompromised patients. Infections include granulomatous amoebic encephalitis or acanthamoeba keratitis.
CSF, brain tissue, or corneal scrapings are the specimen of choice for recovery of this organism. Calcofluor white may be used to stain the cysts present in corneal scrapings. The amoeba is able to invade the CNS from the lower respiratory tract or the skin, particularly in immunocompromised patients. Infections include granulomatous amoebic encephalitis or acanthamoeba keratitis.
Acanthamoeba trophozoites like this one measure 12-45 microns in size and exhibit a sluggish motility with nonprogression. This amoeba has spinelike pseudopodia called acanthopodia, which project outward from the base of the amoeba, and consist of one nucleus witha large karyosome. Cytoplasm is highly vacuolated and granular.
entamoeba histolytica-amoebic dysentery
Structure and Diagnostic Stages:
In addition to performing a wet mount and trichrome stain for diagnosis on suspected stool specimens, material from a sigmoidoscopy or hepatic abscess material may be sent to examine in the same manner to look for E. histolytica. Once an individual ingests an infective cyst, excystation takes place in the small intestine.
One single cyst produces eight motile trophozoites, which settle in the large intestinal lumen, replicating via binary fission and feeding off of living host cells. Sometimes trophozoites migrate to other areas of the body, including the liver, which may result in abscess formation. Infective cysts are passed into the stool and are resistant to many harsh physical conditions. They are able to survive a feces-contaminated environment for up to a month!
Infection and Distribution:
Infection occurs in as much of 10% of the worldwide population, and prevalence is so high in the tropics and subtropics that it is estimated to be at >50%! It is a leading cause of parasitic death only after malaria and schistosomiasis. Many, however, are asymptomatic carriers.
Infection occurs in tropic, subtropic climates, and even colder climates such as Alaska, Canada and Russia. Day-care centers, prisons, hospitals, areas of poor sanitation, and places where feces are used as fertilizer are at higher risk for infection. There are focal epidemics and outbreaks that can pretty much occur anywhere.
Transmission:
Transmission occurs via hand-to-mouth contamination, the fecal-oral route, food or water contamination, and unprotected sex. Flies and cockroaches may also act as vectors (carriers) of the parasite by depositing infective cysts on unprotected food.
Symptoms:
Symptoms include the following: an asymptomatic state, carrier state, amebic colitis (diarrhea, abdominal pain, cramping, chronic weight loss, anorexia, chronic fatigue, flatulence, secondary bacterial infections, ulcers in the colon, cecum, appendix, rectosigmoid area of the intestines, amebic dysentery with bloody diarrhea and pus and mucus), or symptomatic extraintestinal amebiasis (right lobe liver abscess, amebic pneumonitis, liver infection with a cough, upper right abdominal pain, fever, weakness, weight loss, sweating, nausea, vomiting, constipation alternating with diarrhea).
Occasional lung infection, pericardial infection ,splenic infection, skin or brain infection may occur with trophozoite migration. Venereal amebiasis may also occur (penile and/or vaginal).
Pathology caused by this amoeba results in flask-shaped ulcerations of the bowel mucosa, which is what causes the bloody diarrhea. If the amoebae penetrate the intestinal wall and spread through the bloodstream, this is what causes the ulcerations in other tissues of the body, including the liver, lungs, brain, or other, but liver abscesses are the most common, and any of these can be fatal.
Treatment:
Treatment may consist of Chloroquine plus iodoquinol or Flagyl for patients with amebic colitis or liver abscess. Dehydroemetine dihydrochloride is usually administered to patients with amebic dysentery. Asymptomatic patients respond well to uramide, iodoquinol or metronidazole (Flagyl).
Prevention:
Prevention includes making sure water is uncontaminated. Cysts are resistant to routine chlorination, so filtered water with chemically-treated water is important. Proper washing of food products, good personal hygiene and sanitation, protection of food from flies and cockroaches, and avoiding unprotected sex is important for prevention. Of all cases worldwide, only about 10% progress to an invasive stage.
Microscopic Characteristics:
In addition to performing a wet mount and trichrome stain for diagnosis on suspected stool specimens, material from a sigmoidoscopy or hepatic abscess material may be sent to examine in the same manner to look for E. histolytica. Once an individual ingests an infective cyst, excystation takes place in the small intestine.
One single cyst produces eight motile trophozoites, which settle in the large intestinal lumen, replicating via binary fission and feeding off of living host cells. Sometimes trophozoites migrate to other areas of the body, including the liver, which may result in abscess formation. Infective cysts are passed into the stool and are resistant to many harsh physical conditions. They are able to survive a feces-contaminated environment for up to a month!
Infection and Distribution:
Infection occurs in as much of 10% of the worldwide population, and prevalence is so high in the tropics and subtropics that it is estimated to be at >50%! It is a leading cause of parasitic death only after malaria and schistosomiasis. Many, however, are asymptomatic carriers.
Infection occurs in tropic, subtropic climates, and even colder climates such as Alaska, Canada and Russia. Day-care centers, prisons, hospitals, areas of poor sanitation, and places where feces are used as fertilizer are at higher risk for infection. There are focal epidemics and outbreaks that can pretty much occur anywhere.
Transmission:
Transmission occurs via hand-to-mouth contamination, the fecal-oral route, food or water contamination, and unprotected sex. Flies and cockroaches may also act as vectors (carriers) of the parasite by depositing infective cysts on unprotected food.
Symptoms:
Symptoms include the following: an asymptomatic state, carrier state, amebic colitis (diarrhea, abdominal pain, cramping, chronic weight loss, anorexia, chronic fatigue, flatulence, secondary bacterial infections, ulcers in the colon, cecum, appendix, rectosigmoid area of the intestines, amebic dysentery with bloody diarrhea and pus and mucus), or symptomatic extraintestinal amebiasis (right lobe liver abscess, amebic pneumonitis, liver infection with a cough, upper right abdominal pain, fever, weakness, weight loss, sweating, nausea, vomiting, constipation alternating with diarrhea).
Occasional lung infection, pericardial infection ,splenic infection, skin or brain infection may occur with trophozoite migration. Venereal amebiasis may also occur (penile and/or vaginal).
Pathology caused by this amoeba results in flask-shaped ulcerations of the bowel mucosa, which is what causes the bloody diarrhea. If the amoebae penetrate the intestinal wall and spread through the bloodstream, this is what causes the ulcerations in other tissues of the body, including the liver, lungs, brain, or other, but liver abscesses are the most common, and any of these can be fatal.
Treatment:
Treatment may consist of Chloroquine plus iodoquinol or Flagyl for patients with amebic colitis or liver abscess. Dehydroemetine dihydrochloride is usually administered to patients with amebic dysentery. Asymptomatic patients respond well to uramide, iodoquinol or metronidazole (Flagyl).
Prevention:
Prevention includes making sure water is uncontaminated. Cysts are resistant to routine chlorination, so filtered water with chemically-treated water is important. Proper washing of food products, good personal hygiene and sanitation, protection of food from flies and cockroaches, and avoiding unprotected sex is important for prevention. Of all cases worldwide, only about 10% progress to an invasive stage.
Microscopic Characteristics:
- Trophozoites (found in fresh, loose feces)
- May ingest red blood cells (differential diagnosis)
- Only one that ingests RBC's!
- 8-65 microns (average 12-25 microns)
- Move via pseudopods (thin, pointed)
- Active, progressive motility in saline wet mount
- Single, large nucleus
- Evenly distributed fine, granular peripheral nuclear chromatin like ground glass and a small, central karyosome/endosome
- The chromatin may resemble bicycle spokes, radiating outward from the karyosome to the nuclear membrane
- May contain vacuoles
- May ingest red blood cells (differential diagnosis)
- Cysts (can be found outside the host in water, soil and food)
- Killed by heat and freezing
- Survive a few months outside of host
- Cause infection in the host by excysting in the host's digestive tract, releasing the trophozoite stage
- Have up to a maximum of 4 nuclei (1-4)
- May contain chromatoid bodies (look like bars or cigars) (diagnostic)
- E. histolytica/dispar
- May contain ingested red blood cells
- Perfectly round, 10-20 micrometers
entamoeba coli-non-pathogen
E. coli cyst with 8 nuclei is seen here. The cysts vary in size from 8-35 microns, with an average of 12-25 microns. A thick cell wall surrounds the round cyst and the nuclei are highly apparent and visible. Large cysts may contain as many as 16 or more nuclei (supercysts). The granular cytoplasm may contain thin, splinter-like chromatoid bars with pointed ends. A glycogen mass may be present.
E. coli trophozoite. Trophozoites are large and measure from 18-27 microns, but may be as small as 12 microns or as large as 55 microns. The trophozoite moves by blunt pseudopods which exhibit a sluggish, nonprogressive motility. The single nucleus is recognizable and the karyosome and peripheral chromatin appear as refractile. The large nucleus contains an irregular-shaped karyosome surrounded by unevenly distributed peripheral chromatin. This trophozoite may contain vacuoles with ingested bacteria, but not RBCs.
Examination of stool wet mount and trichrome stain is the method of choice for recovery of E. coli cysts and trophozoites. They are not pathogenic, but their presence suggests ingestion of contaminated water or food, and the parasitologist should carefully examine the slide for the presence of pathogenic parasites as well.
E. coli is found worldwide in both warm and cold climates.
Microscopic Appearance:
E. coli is found worldwide in both warm and cold climates.
Microscopic Appearance:
- Trophozoites:
- One large nucleus surrounded by a thick membrane
- Granular cytoplasm
- Irregular karyosome that is large and eccentric
- Chromatin is clumped and uneven
- Wide, tapered pseudopods that are blunt at the ends
- Ingest bacteria
- Sluggish motility
- One large nucleus surrounded by a thick membrane
- Cysts:
- Immature form
- May have 4 nuclei like the cyst of E. histolytica, but it is larger and has more granular chromatin
- May have 4 nuclei like the cyst of E. histolytica, but it is larger and has more granular chromatin
- Mature form
- 8 nuclei
- May have chromatid bars, but they are thin and splintered with pointed rather than blunt ends
- 8 nuclei
- 10-35 micrometers
- Not perfectly round and may even be oval
- Survive longer than the cysts of E. histolytica (survive outside the host 3-4 months)
- Infective stage
- Immature form
entamoeba hartmanni-nonpathogen
- Nonpathogen
- Cysts are <10 micrometers
- Trophozoites are <12 micrometers
E. hartmannii trophozoite. The typical trophozoite measures just 8-12 microns, with a range of 5-15 microns, smaller than that of E. histolytica. Finger-like pseudopods exhibit a progressive motility. Trophozoites like this one house one nucleus that is visible only in stained slides. The peripheral chromatin is evenly distributed and granulytic with a beaded appearance. The karyosome is central or eccentric. Nuclear material is similar to that of E. histolytica. The trophozoite may ingest bacteria, but not RBCs.
E. hartmannii trophozoite. E. hartmanni is nonpathogenic, but it is important to recognize it to be able to differentiate it from E. histolytica and its presence may indicate exposure to contaminated water, therefore, the parasitologist must carefully examine the slide for the presence of pathogenic organisms as well. Individuals infected with this organism are typically asymptomatic.
E. hartmannii cyst in iodine wet mount. E. hartmanni cysts range from 5-12 microns with an average size of 7-9 microns. The round cysts may contain 1, 2, 3 or 4 nuclei, similar to E. histolytica. The chromatoid material is unorganized and young cysts contain a diffuse glyogen mass. The cytoplasm is finely granular. Mature cysts usually have round-ended chromatoid bars similar to those of E. histolytica.
entamoeba polecki-nonpathogen
- Nonpathogen
- Trophozoites:
- The average E. polecki trophozoite measures 12-20 microns but may vary in size ranging from 8-25 microns.
- The trophozoites exhibit a sluggish, nonprogressive motility in stools of normal consistency. In diarrheal stools, however, trophozoites may exhibit progressive, undirectional motility.
- There is a single nucleus similar to E. histolytica and E. coli.
- Vacuoles may be present that contain ingested yeast, bacteria or other food particles, but not RBCs.
- The average E. polecki trophozoite measures 12-20 microns but may vary in size ranging from 8-25 microns.
- Cysts:
- Range from 10-20 microns and are spherical to oval in shape.
- Cysts contain just one nucleus with a small, central karyosome surrounded by fine, evenly distributed peripheral chromatin.
- There may be thin chromatoid bars with pointed or angular ends.
- A diffuse glycogen mass may be present.
- Range from 10-20 microns and are spherical to oval in shape.
Human infections are quite rare and only found in select areas of the world. Most cases are asymptomatic.
naegleria fowleri-meningitis; primary amoebic encephalitis; death
N. fowleri is the only amoeba with THREE morphological forms: amoeboid trophozoite, flagellate trophozoite and cyst. Microscopic examination of CSF is the method of choice for recovery of ameboid trophozoites. Saline and iodine wet mounts are recommended. Samples of tissue, brain material and nasal discharge may also be examined. When cultured, this amoeba may show a characteristic trailing effect when placed on agar plates that have been prepared with GN bacilli. The ameboid trophozoites are the only form known to exist in human beings and they replicate via binary fission. Humans contract the amoeba by swimming in contaminated water, where the trophozoites enter through the nasal passages and travel to the brain, rapidly causing tissue destruction and often, death. This is called naegleriasis or primary amoebic meningoencephalitis. This parasite is found in warm bodies of water, such as lakes, ponds, streams, swimming pools and the ocean. Cases have also occurred via inhalation of contaminated dust particles. This parasite infection results in primary amebic meningoencephalitis when invasion of the brain occurs with rapid tissue destruction. Symptoms include fever, headache, back pain, sore throat, nausea, vomiting, hallucinations, confusion, meningitis with stiff neck, and seizures. Smell and taste alterations, confusion, stuffy nose, and a positive Kernig's sign also occur. Death occurs in 3-6 days after onset of symptoms if infection goes untreated, and often with treatment as well. Amoebic drugs are not very effective against this amoeba. The mortality rate is 98.5%.
Lakes and rivers and ponds and even hot springs have contributed to infection and death, especially during warm months and algae blooms. It is found in freshwater, untreated, unchlorinated or under-chlorinated water. Please be careful when swimming in this type of water. It is best not to swim underwater without nose, ear and eye protection. Never drink or swallow this type of water.
Lakes and rivers and ponds and even hot springs have contributed to infection and death, especially during warm months and algae blooms. It is found in freshwater, untreated, unchlorinated or under-chlorinated water. Please be careful when swimming in this type of water. It is best not to swim underwater without nose, ear and eye protection. Never drink or swallow this type of water.
iodamoeba buetschlii-non-pathogen
I. butschlii is found worldwide, mostly in tropical areas. Transmission is ingestion of contaminated food or water. It is considered to be a nonpathogen that produces no symptoms. It contains a large, eccentric karyosome and nucleus, and a large central glycogen vacuole.
endolimax nana-non-pathogen
E. nana is usually found in warm, moist, tropic regions of the world and areas where poor hygiene and sanitation occur. Contaminated food or water serves as the main source of transmission of this parasite, and infections are typically asymptomatic. It is considered a nonpathogen. Protection of food from flies and cockroaches is essential.
the flagellates
dientamoeba fragilis-amebiasis
Dientamoeba fragilis is a motile organism that moves via pseudopods alone, though it does exhibit internal flagellate characteristics (it has no external flagella). It does show progressive motility. The typical trophozoite measures about 8-12 microns, though it ranges from 5-18 microns, and is irregular in shape, round-to-oval. It contains 2 nuclei, each nuclei containing 4-8 centrally located massed chromatin granules. There is no peripheral chromatin. Mononucleated forms also exist (one nucleus). Some trophozoites contain vacuoles with ingested bacteria, but no RBCs.
Once ingested, it thrives in the large intestine in the mucosal crypts. It is estimated that most people infected with D. fragilis are asymptomatic. Those who suffer from symptoms typically present with abdominal pain and diarrhea, occasional bloody or mucoid stools, diarrhea alternating with constipation, flatulence, nausea, weakness, vomiting, weight loss, and/or fatigue and some patients also experience itching and low-grade eosinophilia.
Once ingested, it thrives in the large intestine in the mucosal crypts. It is estimated that most people infected with D. fragilis are asymptomatic. Those who suffer from symptoms typically present with abdominal pain and diarrhea, occasional bloody or mucoid stools, diarrhea alternating with constipation, flatulence, nausea, weakness, vomiting, weight loss, and/or fatigue and some patients also experience itching and low-grade eosinophilia.
giardia lamblia-giardiasis
Motility: Tumbling motility (like a falling leaf)
The specimen of choice for recovery of trophozoites and cysts is stool, but it is usually shed in "showers", meaning that many organisms may be passed at one time and recovered one day, and then none the next, therefore, it is best to collect multiple samples from a patient for the best collection. Other specimens for analyzation may be collected, including duodenal contents (aspirate), and upper small intestinal biopsies.
Infection occurs via ingestion of contaminated food or water containing cysts. After ingestion, the cysts enter the stomach, where the gastric acid and digestive juices promote the cysts to excyst in the duodenum. Trophozoites become established there and multiply every 8 hours via binary fission, where they feed by attaching their sucking disks to the intestinal mucosa of the duodenum. They may travel to the gallbladder and common bile duct as well, as well as to the large bowel, where they are excreted into the feces, where they may remain viable in fecal material for up to 3 months in a watery environment.
G. lamblia is found worldwide in lakes, streams, ponds, and other sources of water. It's considered to be one of the most common intestinal parasites there is, particularly amongst kids, and ingestion of contaminated water is the major cause of infection. It can cause outbreaks of diarrhea. Cysts are resistant to typical chlorination processes that most swimming pools and water treatment plants perform so filtration of water in addition to chemical treatment is key to elimination of the parasite. Consumption of contaminated fruit or vegetables is also a source of transmission, as well as person-to-person contact through oral-anal sexual practices or via the fecal-oral route also serving as routes of transmission.
Individuals at higher risk of infection include children at daycare centers, those living in poor sanitary conditions, travel to endemic areas, unprotected sex, the immunocompromised, and those in close contact with infected domestic sheep, cattle or dogs.
Symptoms of infection include the following: asymptomatic state, giardiasis or "traveler's diarrhea", mild diarrhea, abdominal cramps, anorexia, flatulence, tender epigastric region, steatorrhea, malabsorption syndrome, and possible production of light-colored stools with a high fat content, along with fat-soluble vitamin deficiencies, folic acid deficiencies, pernicious anemia, hypoproteinemia, hypogammaglobulinemia, and changes in the intestinal villi. There is rarely ever bloody stools in infected patients, however.
The incubation period ranges from 10-36 days. Symptoms begin with watery, foul-smelling diarrhea with steatorrhea, flatulence, and terrible abdominal cramps. The infection is typically self-limiting in about 10-14 days, but chronic cases have been known to occur, particularly in patients with diverticuli or those with IgA deficiency.
The specimen of choice for recovery of trophozoites and cysts is stool, but it is usually shed in "showers", meaning that many organisms may be passed at one time and recovered one day, and then none the next, therefore, it is best to collect multiple samples from a patient for the best collection. Other specimens for analyzation may be collected, including duodenal contents (aspirate), and upper small intestinal biopsies.
Infection occurs via ingestion of contaminated food or water containing cysts. After ingestion, the cysts enter the stomach, where the gastric acid and digestive juices promote the cysts to excyst in the duodenum. Trophozoites become established there and multiply every 8 hours via binary fission, where they feed by attaching their sucking disks to the intestinal mucosa of the duodenum. They may travel to the gallbladder and common bile duct as well, as well as to the large bowel, where they are excreted into the feces, where they may remain viable in fecal material for up to 3 months in a watery environment.
G. lamblia is found worldwide in lakes, streams, ponds, and other sources of water. It's considered to be one of the most common intestinal parasites there is, particularly amongst kids, and ingestion of contaminated water is the major cause of infection. It can cause outbreaks of diarrhea. Cysts are resistant to typical chlorination processes that most swimming pools and water treatment plants perform so filtration of water in addition to chemical treatment is key to elimination of the parasite. Consumption of contaminated fruit or vegetables is also a source of transmission, as well as person-to-person contact through oral-anal sexual practices or via the fecal-oral route also serving as routes of transmission.
Individuals at higher risk of infection include children at daycare centers, those living in poor sanitary conditions, travel to endemic areas, unprotected sex, the immunocompromised, and those in close contact with infected domestic sheep, cattle or dogs.
Symptoms of infection include the following: asymptomatic state, giardiasis or "traveler's diarrhea", mild diarrhea, abdominal cramps, anorexia, flatulence, tender epigastric region, steatorrhea, malabsorption syndrome, and possible production of light-colored stools with a high fat content, along with fat-soluble vitamin deficiencies, folic acid deficiencies, pernicious anemia, hypoproteinemia, hypogammaglobulinemia, and changes in the intestinal villi. There is rarely ever bloody stools in infected patients, however.
The incubation period ranges from 10-36 days. Symptoms begin with watery, foul-smelling diarrhea with steatorrhea, flatulence, and terrible abdominal cramps. The infection is typically self-limiting in about 10-14 days, but chronic cases have been known to occur, particularly in patients with diverticuli or those with IgA deficiency.
yeast cells in o & p wet mount versus giardia lamblia cysts:
Sometimes it can be difficult for the inexperienced tech to differentiate between Giardia lamblia cysts and yeast cells in iodine wet mount preparations. The Giardia lamblia cyst is oval to ellipsoid in shape, and it measures approximately 8-19 micrometers (average 10-14 micrometers). Immature cysts have 2 nuclei, and mature cysts have 4 nuclei. Nuclei and fibrils are visible in wet mount and iodine wet mount preparations and in Trichrome stains. It almost looks as if there is a face within the Giardia lamblia cyst. Yeast cells measure 10-12 micrometers.
chilomastix mesnili-non-pathogen
Motility: Rotary
Chilomastix mesnili is a pear-shaped trophozoite measuring from 5-25 microns in length by 5-10 microns in width with an average of 8-15 microns long. The motility is a stiff, rotary motion in a directional pattern. Trophozoites contain a single nucleus with a small karyosome found in the center or eccentrically located. Chromatin granules form plaques against the nuclear membrane. There is no peripheral chromatin. Trophozoites typically exhibit 4 flagella, 3 of which extend from the anterior end of the parasite. The 4th flagella is short and extends from the cytostome posteriorly. There is a spiral groove present in a curved posture at the posterior end of the trophozoite, an indentation that extends down the center of the body at the posterior (back) end.
The cysts are oval and lemon-shaped, and have an anterior knob. The cysts average about 7-10 microns in length by 3-7 microns in width, and contain a large, single nucleus with a large, central karyosome. Again, there is no peripheral chromatin.
Infections with this organism are typically asymptomatic and transmission is primarily through hand-to-mouth contamination or by ingesting contaminated food or water. This organism is considered to be a nonpathogen.
Chilomastix mesnili is a pear-shaped trophozoite measuring from 5-25 microns in length by 5-10 microns in width with an average of 8-15 microns long. The motility is a stiff, rotary motion in a directional pattern. Trophozoites contain a single nucleus with a small karyosome found in the center or eccentrically located. Chromatin granules form plaques against the nuclear membrane. There is no peripheral chromatin. Trophozoites typically exhibit 4 flagella, 3 of which extend from the anterior end of the parasite. The 4th flagella is short and extends from the cytostome posteriorly. There is a spiral groove present in a curved posture at the posterior end of the trophozoite, an indentation that extends down the center of the body at the posterior (back) end.
The cysts are oval and lemon-shaped, and have an anterior knob. The cysts average about 7-10 microns in length by 3-7 microns in width, and contain a large, single nucleus with a large, central karyosome. Again, there is no peripheral chromatin.
Infections with this organism are typically asymptomatic and transmission is primarily through hand-to-mouth contamination or by ingesting contaminated food or water. This organism is considered to be a nonpathogen.
trichomonas vaginalis-vaginitis-
Motility: Rotary, Spinning, Zig-zag
Trichomonas vaginalis exists only in trophozoite form, and is not found in a cyst form or stage. Trophozoites may grow up to 30 microns in length and are pear-shaped to oval, exhibiting a rapid, jerky, rotary, spinning, or zig-zag-like motility aided by their 4-6 flagella, all originating from the anterior (front) end, with the exception of one, extending from the posterior end (posterior axostyle). There is a characteristic undulating membrane (short), that extends only one half the length of the body, and it has a single nucleus that is oval in shape.
Trophozoites may be recovered in spun urine, vaginal and urethral discharges, and prostatic secretions. Trichomonas vaginalis trophozoites live on the mucosa of the vagina in infected women and they multiply by binary fission. They eat and live on local commensal flora (bacteria) and leukocytes (white blood cells). They thrive in a slightly alkaline environment or slightly acidic environment. In males, the trohpozoites infect the prostate gland region and the urethral epithelium. Infections occur worldwide and the major mode of transmission is unprotected sexual intercourse. They can also infect an unborn child if the mother is infected during pregnancy or during the birthing process. Additionally, if conditions are just right, transmission can occur via contaminated toilet articles or underclothes, wet sponges, damp towels, and can survive in water for up to 40 minutes. Asymptomatic/carrier states exist, but most frequently occur in men.
Chronic urethritis or recurring urethritis may produce symptoms in men, and may involve the seminal vesicles, urogenital tract, and prostate. An enlarged and tender prostate, dysuria, nocturia, and epididymitis are conditions that infected men may experience, and patients often release a white, thin, urethral discharge containing the trophozoites.
In women, symptoms include persistent, chronic vaginitis with a foul-smelling, greenish-yellow, frothy discharge. The incubation period is 4-28 days. Symptoms may include burning, itching, chafing, red punctate lesions, dysuria, and increased frequency of urination.
Infants infected may suffer from respiratory infections and conjunctivitis and are most likely contracted as a result of migration of the trophozoites through the birth canal before or during birth.
Trichomonas vaginalis exists only in trophozoite form, and is not found in a cyst form or stage. Trophozoites may grow up to 30 microns in length and are pear-shaped to oval, exhibiting a rapid, jerky, rotary, spinning, or zig-zag-like motility aided by their 4-6 flagella, all originating from the anterior (front) end, with the exception of one, extending from the posterior end (posterior axostyle). There is a characteristic undulating membrane (short), that extends only one half the length of the body, and it has a single nucleus that is oval in shape.
Trophozoites may be recovered in spun urine, vaginal and urethral discharges, and prostatic secretions. Trichomonas vaginalis trophozoites live on the mucosa of the vagina in infected women and they multiply by binary fission. They eat and live on local commensal flora (bacteria) and leukocytes (white blood cells). They thrive in a slightly alkaline environment or slightly acidic environment. In males, the trohpozoites infect the prostate gland region and the urethral epithelium. Infections occur worldwide and the major mode of transmission is unprotected sexual intercourse. They can also infect an unborn child if the mother is infected during pregnancy or during the birthing process. Additionally, if conditions are just right, transmission can occur via contaminated toilet articles or underclothes, wet sponges, damp towels, and can survive in water for up to 40 minutes. Asymptomatic/carrier states exist, but most frequently occur in men.
Chronic urethritis or recurring urethritis may produce symptoms in men, and may involve the seminal vesicles, urogenital tract, and prostate. An enlarged and tender prostate, dysuria, nocturia, and epididymitis are conditions that infected men may experience, and patients often release a white, thin, urethral discharge containing the trophozoites.
In women, symptoms include persistent, chronic vaginitis with a foul-smelling, greenish-yellow, frothy discharge. The incubation period is 4-28 days. Symptoms may include burning, itching, chafing, red punctate lesions, dysuria, and increased frequency of urination.
Infants infected may suffer from respiratory infections and conjunctivitis and are most likely contracted as a result of migration of the trophozoites through the birth canal before or during birth.
This parasite is found in Africa, Asia, South America, and exhibits no periodicity. It is carried by the Cyclops fly. Adult worms live in the subcutaneous tissues. Females migrate throughout the body and larvae are released from an ulcer in the skin. Ingestion of water containing crustaceans infected with larvae causes infection. A major allergic reaction throughout the body results in symptoms and local ulcer formation.
Protozoa: The hemoflagellates: leishmania spp; trypanosoma spp
Important Terminology:
Types of Leishmania Species:
Types of Trypanosoma Species:
Examine multiple thick and thin blood smears stained with Wright and Giemsa stains.
- Amastigote: nonflagellated, small, oval-shaped form in the life cycle of Trypanosoma spp
- Mitochondrial kinetoplastid
- Large nucleus
- L.D. body (Leishmanial form)
- Multiply rapidly in macrophages of the reticuloendothelial system in tissues such as the heart, liver, or spleen, and can be deadly
- Mitochondrial kinetoplastid
- Arthropod: insect vector or carrier
- Blepharoplast: basal body where the flagella originates
- Supports the undulating membrane (kinetoplastid flagellates)
- Supports the undulating membrane (kinetoplastid flagellates)
- Cutaneous: skin
- Diffuse Disseminated Cutaneous Leishmaniasis: chronic form of Leishmaniasis
- Ethiopia and Kenya
- Central and South America
- Non-ulcerating, non-necrotizing skin lesions all over the body
- Ethiopia and Kenya
- Epimastigote: flagellated, flat, spindle-shaped form
- Found primarily in the gut of the reduviid bug or salivary glands of the tsetse fly carriers of trypanosomes
- Undulating membrane extending from the flagellum
- Small kinetoplastid just anterior to the larger nucleus in the middle
- Found primarily in the gut of the reduviid bug or salivary glands of the tsetse fly carriers of trypanosomes
- Kinetoplast: accessory body in many protozoans
- Large mitochondrion next to the basal granule of the undulating membrane flagellum
- Contains mitochondrial DNA
- Large mitochondrion next to the basal granule of the undulating membrane flagellum
- Leishman-Donovan (L.D.) Body: another term for the amastigote forms found in tissue macrophages of the liver and spleen with infection caused by Leishmania donovani
- Promastigote: flagellated form of Trypanosoma
- Kinetoplast is found at the anterior end
- no undulating membrane
- Found in the midgut and pharynx of the sandfly vectors of leishmania spp
- Kinetoplast is found at the anterior end
- Pseudocyst: in the heart muscle, contains amastigote stages
- Romana's Sign: periorbital edema resulting from the bite of a reduviid bug, a sign of Chagas disease, when the bite occurs near the eye or on the conjunctiva
- Trypomastigote: flagellated form
- Kinetoplast is found at the posterior end
- Undulating membrane extends along the entire body from the flagellum (anterior end)
- Seen in the blood of infected humans, or in plasma, tissues, lymph nodes, or the CNS
- Infective stage
- C-shaped in T. cruzi
- Kinetoplast is found at the posterior end
- Subpatent: subclinical; no symptoms; asymptomatic
- Winterbottom's Sign: swelling of the cervical lymph nodes along the back of the neck due to infection with trypanosomes, which occurs early during infection, and causes inflammation
- Associated with T. brucei gambiense, T. brucei rhodiense
- Associated with T. brucei gambiense, T. brucei rhodiense
- Xenodiagnosis: an interesting test in which T. cruzi infection is diagnosed by placing an uninfected reduviid bug on an infected individual, allowing it to feed, then examining the insect's feces for trypomastigote forms
Types of Leishmania Species:
- All are transmitted by the sandfly.
- The most common form is cutaneous leishmaniasis.
- It creates a lesion that self-heals or an ulcer that may last up to a year.
- Amastigote forms are found multiplying inside macrophages of the lesion.
- Leishmania tropica complex
- Oriental Boil
- Baghdad Boil
- Delhi Boil
- Old World Leishmaniasis
- Cutaneous, spontaneous healing ulcers
- Dx: amastigotes in macrophages of the skin lesion
- Oriental Boil
- Leishmania mexicana
- New World Leishmaniasis
- Diffuse Cutaneous Leishmaniasis
- 1.5 million cases
- Cutaneous, spontaneous healing ulcers
- Dx: amastigotes in macrophages of the skin lesion
- Some rare cases in the USA have been reported in TX and OK due to the woodrat reservoir and the bite of the sandfly
- New World Leishmaniasis
- Leishmania braziliensis
- New World Leishmaniasis
- Affects the mucosa of the nasopharynx and mouth
- Mucocutaneous Leishmaniasis
- May be subpatent, but flare up years later, eroding the nasal and ear cartilage
- Dx: amastigotes at the periphery of the skin lesion or L.D. bodies in the reticuloendothelial system, spleen, lymph nodes, bone marrow, liver, nasal discharges, feces, urine
- Signs: elevated gamma globulin
- New World Leishmaniasis
- Leishmania donovani
- Kala-azar
- Dum-dum fever
- Widespread and not localized like the other types
- Spread to the viscera (Visceral Leishmaniasis)
- Multiply in macrophages of ALL internal organs and tissues
- Can be deadly
- Amastigote forms are seen as L.D. bodies
- Kala-azar
Types of Trypanosoma Species:
Examine multiple thick and thin blood smears stained with Wright and Giemsa stains.
- Trypanosoma brucei rhodesiense
- East African Sleeping Sickness
- 50,000 cases annually
- Transmitted by the tsetse fly (Glossina spp)
- Trypomastigotes enter the blood when the infected fly takes a blood meal
- Symptoms: fever, headache, muscle and joint pain, night sweats, CNS impairment in approximately 1 month with motor changes and lethargy
- Complications: coma, cardiac failure, death
- Dx: trypomastigotes in peripheral blood, lymph nodes or CNS (examine fluid or buffy coat)
- Winterbottom's Sign (enlarged cervical lymph nodes)
- Signs: autoagglutination of red blood cells; elevated levels of IgM in CSF; ELISA antigen test is positive
- East African Sleeping Sickness
- Trypanosoma brucei gambiense
- West African Sleeping Sickness
- 50,000 cases annually
- Transmitted by the tsetse fly
- Trypomastigotes enter the blood when the infected fly takes a blood meal
- Symptoms: fever, headache, muscle and joint pain, night sweats, CNS impairment in approximately 6 months to 1 year with motor changes and lethargy
- Complications: coma, death
- Dx: trypomastigotes in peripheral blood, lymph nodes or CNS (examine fluid or buffy coat)
- Winterbottom's Sign (enlarged cervical lymph nodes)
- Signs: autoagglutination of red blood cells; elevated levels of IgM in CSF; ELISA antigen test is positive
- Has been known to be acquired via a blood transfusion or organ transplant
- This organism can cross the placenta of pregnant women and cause disease to the neonate
- West African Sleeping Sickness
- Trypanosoma cruzi
- Chagas Disease
- American trypanosomiasis
- 200,000 cases annually, primarily in Central and South America, Southern USA, Mexico
- Transmitted by the reduviid (Triatoma) or "kissing" bug when the infected bug bites a human, then deposits its feces on the skin, where it is rubbed into the wound
- Tend to feed at night on warm-blooded host mammals
- Often feed on the conjunctiva of the eye
- Tend to feed at night on warm-blooded host mammals
- Multiply in macrophages of the reticuloendothelial system as the amastigote form in tissues such as the heart
- Dx: C-shaped trypomastigote forms are found in the bloodstream or amastigotes are found in the stained tissue scrapings of the chagoma lesion at the site of the bite or in heart muscle tissue postmortem
- Can cause an enlarged heart, esophagus, and colon
- Can cause death if left untreated
- Acute, fatal disease in children and may cause periorbital edema if bitten near the eye (Romana's sign), cardiac ganglia destruction, megacolon, rapid death
- Chagas Disease
leishmania-leishmaniasis; mucocutaneous, visceral
tissue nematodes: filariae
Adult filariae: live in various human tissues
Fertilized adult female filariae: live in tissues and produce living embryos
Microfilariae: living embryos in tissues produced by fertilized adult female filariae, which migrate into the lymphatic system or bloodstream or skin. They exhibit periodicity (found more often in the peripheral bloodstream at certain times of the day or night), which correlates with the feeding times and patterns of the intermediate arthropod host. This is the infective stage and the diagnostic stage.
They require an intermediate host to complete their life cycle and transmit infection
Differentiation of microfilariae on a stained blood smear is examined for the following:
No Nuclei in Tip of Tail: Nuclei in Tail:
W. bancrofti (also, sheath present) Loa loa (also, sheath present; continuous row of posterior nuclei)
Mansonella ozzardi (no sheath) Brugia malayi (sheath present) (nuclei not continuous, but there are 2 at the tip of the tail)
Onchocerca volvulus (no sheath) Mansonella perstans (no sheath) (nuclei in tip of tail to the very end)
Fertilized adult female filariae: live in tissues and produce living embryos
Microfilariae: living embryos in tissues produced by fertilized adult female filariae, which migrate into the lymphatic system or bloodstream or skin. They exhibit periodicity (found more often in the peripheral bloodstream at certain times of the day or night), which correlates with the feeding times and patterns of the intermediate arthropod host. This is the infective stage and the diagnostic stage.
They require an intermediate host to complete their life cycle and transmit infection
- Arthropod intermediate host ingests microfilariae when taking a blood meal
- Larvae molt 2x inside the arthropod host
- Larvae molt into the infective stage: filariform larvae
- Filariform larvae are released from the insect and enter a human definitive host during the next blood meal
- Filariform larvae migrate to tissue site and mature into adults, which can take up to a year
Differentiation of microfilariae on a stained blood smear is examined for the following:
- Presence or absence of a sheath
- Examination of the tail area for cells that exhibit a characteristic pattern of the nuclei (whether they are in the tail tip or not and how many)
- Observation of the presence and size of the cephalic space, nerve ring, excretory pore, and anal pore
- Whether the tail is straight and pointed or bent like a fish hook
No Nuclei in Tip of Tail: Nuclei in Tail:
W. bancrofti (also, sheath present) Loa loa (also, sheath present; continuous row of posterior nuclei)
Mansonella ozzardi (no sheath) Brugia malayi (sheath present) (nuclei not continuous, but there are 2 at the tip of the tail)
Onchocerca volvulus (no sheath) Mansonella perstans (no sheath) (nuclei in tip of tail to the very end)
loa loa-filariasis; eyeworm
- Sheathed
- Nuclei in tail (continuous row of posterior nuclei)
- Microfilariae found in blood
- Found in Africa (endemic)
- Exhibits diurnal periodicity
- Carried by the Chrysops fly
- Adults migrate to the subcutaneous tissues
- Chronic or benign disease
- Calabar swellings
- Eyeworm
Loa loa is found in Africa and exhibits diurnal periodicity. It is carried by the Chrysops fly (deer fly), which is larger than the typical house fly and is found in Africa and in rainforest areas. Adult worms bore their way through the subcutaneous tissues. Microfilariae live in the blood. The vector is a blood-sucking fly that transmits the parasite to the human host.
onchocerca volvulus-filariasis; river blindness
This parasite is found in Central America and in Africa and does not exhibit any periodicity. It is carried by the Simulium fly (black fly), also a blood-sucking fly. Adults reside in fibrotic nodules and microfilariae migrate subcutaneously. Disease is chronic and nonfatal, however, allergy to the microfilariae results in a host of local symptoms and may result in blindness.
trypanosoma - Chagas' Disease; west african sleeping sickness; hemolymphatic disease; cns disease; east african sleeping sickness
Trypanosoma brucei gambiense and T. b. rhodesiense are endemic in Central Africa and south of the Sahara from West Africa, and cause African trypanosomiasis, or African Sleeping Sickness.
Trypanosoma cruzi causes Chagas' Disease and occurs only in the Western hemisphere, in the southern USA and California southward to Argentina.
Trypanosoma rangeli occurs in Central and South America and causes non-pathogenic trypanosomiasis.
Trypanosoma cruzi causes Chagas' Disease and occurs only in the Western hemisphere, in the southern USA and California southward to Argentina.
Trypanosoma rangeli occurs in Central and South America and causes non-pathogenic trypanosomiasis.
brugia malayi-filariasis
This parasite is found in the Far East, exhibits nocturnal periodicity and is carried by the Anopheles spp and Mansonia spp mosquitoes. The Brugia spp human filariae are found in the Lesser Sunda Islands of Indonesia and Zaire in Central Africa. B. timori adult worms are recovered in lymphatic vessels, whereas the microfilariae are found in the blood. There is no prominent constriction near the end of the tail. Between the subterminal and terminal nuclei is a gap.
mansonella spp-filariasis
Mansonella species microfilaria are found in West and central Africa, parts of east Africa, many parts of South America, and areas of the Caribbean Islands. Adult worms make their home in body cavities, mesenteries and perirenal tissues of humans. The microfilariae circulate throughout the bloodstream.
Mansonella perstans adult males measure 45 mm by 60 microns and females measure 70-80 mm by 120 microns. The microfilariae are unsheathed. They measure 190-200 microns with a tail that tapers with a bluntly rounded end. The nuclei extend to the end of the tail. The microfilariae that circulate in the blood are picked up by biting midges (Culicoides spp). It takes about 7-10 days for the microfilariae to develop to the infective stage.
Mansonella ozzardi causes mansonellosis. It is found in South and Central America, Mexico and the West Indies. Adult worms live in the subcutaneous tissues and microfilariae circulate in the blood. The adult worms are long and skinny and thread-like, males measuring 24-28 mm by 0.07-0.08 mm, and females measure 32-62 mm by 0.13-0.16 mm. The microfilariae are unsheathed and small, measuring 163-204 microns by 3-4 microns with a long, slender tail and a nuclear column that ends short of the end of the tail. The tail ends in a bent, "button hook-like" formation. Biting midges serve as vectors and black flies also serve as vectors. It takes 5-9 days for the microfilariae to develop to the infective stage.
Mansonella perstans adult males measure 45 mm by 60 microns and females measure 70-80 mm by 120 microns. The microfilariae are unsheathed. They measure 190-200 microns with a tail that tapers with a bluntly rounded end. The nuclei extend to the end of the tail. The microfilariae that circulate in the blood are picked up by biting midges (Culicoides spp). It takes about 7-10 days for the microfilariae to develop to the infective stage.
Mansonella ozzardi causes mansonellosis. It is found in South and Central America, Mexico and the West Indies. Adult worms live in the subcutaneous tissues and microfilariae circulate in the blood. The adult worms are long and skinny and thread-like, males measuring 24-28 mm by 0.07-0.08 mm, and females measure 32-62 mm by 0.13-0.16 mm. The microfilariae are unsheathed and small, measuring 163-204 microns by 3-4 microns with a long, slender tail and a nuclear column that ends short of the end of the tail. The tail ends in a bent, "button hook-like" formation. Biting midges serve as vectors and black flies also serve as vectors. It takes 5-9 days for the microfilariae to develop to the infective stage.
wuchereria bancrofti-filariasis; elephantitis; bancroft's filaria
This parasite is found in the tropics, exhibits nocturnal periodicity and is carried by the Culex, Aedes, and Anopheles mosquitoes. Adult worms live in the lymphatic system, whereas the microfilariae live in the blood. It results in granulomatous lesions, fever and chills, eosinophilia and elephantitis.
Trypanosoma cruzi and chagas disease:
According to the CDC, in 1909, the Brazilian physician Carlos Chagas, discovered Chagas Disease, caused by the blood parasite Trypanosoma cruzi. Insect vectors, particularly the reduviid bug, or kissing bug, also known as the triatomine bug, carry the parasite. This vector can transmit the disease to humans and animals with its feces and bite, and it is found only in the Americas. The disease is known as American trypanosomiasis, or Chagas Disease.
The insect thrives in homes made of mud, adobe, thatch and straw. But it can also be found in modern American homes and in the outdoors. During the day, they tend to hide out in crevices and in roofs. At night, the bugs emerge, and tend to bite humans while they are sleeping. Since the bugs tend to bite the face, they are referred to as "kissing bugs".
The CDC estimates that around 8 million people become infected with this disease each year across Mexico, Central, South and North America. In many cases, infections are asymptomatic, so people are unaware they are infected. Left untreated, however, the infection can remain lifelong and can even become life-threatening.
Transmission occurs several ways:
The trypomastigote, as seen in the blood slide below, is the diagnostic and infectious stage. A CBC is collected and the hematology laboratory and pathologists observe for the trypomastigotes, which are diagnostic for this disease.
The insect thrives in homes made of mud, adobe, thatch and straw. But it can also be found in modern American homes and in the outdoors. During the day, they tend to hide out in crevices and in roofs. At night, the bugs emerge, and tend to bite humans while they are sleeping. Since the bugs tend to bite the face, they are referred to as "kissing bugs".
The CDC estimates that around 8 million people become infected with this disease each year across Mexico, Central, South and North America. In many cases, infections are asymptomatic, so people are unaware they are infected. Left untreated, however, the infection can remain lifelong and can even become life-threatening.
Transmission occurs several ways:
- The bug passes the parasite in its feces, bites the animal or human, takes a blood meal, then when the animal or human goes to rub or scratch it, the feces gets inside the wound, spreading the disease
- Congenital transmission (pregnant mother to fetus via the placenta)
- Blood transfusion
- Organ transplant
- Consumption of uncooked food that has been contaminated with the insect's feces
- Accidental laboratory exposure
- Romana's sign (swelling of the eyelid)
- Lasts a few weeks to a few months
- Asymptomatic or mild symptoms
- Fever
- Fatigue
- Body aches
- Headache
- Rash
- Loss of appetite
- Diarrhea
- Vomiting
- Mild hepatosplenomegaly
- Swollen glands
- Chagoma (swelling)
- Rare: myocarditis or meningoencephalitis
- Cardiac complications, including enlarged heart, heart palpitations, failure, or cardiac arrest
- GI complications, including esophageal enlargement, megacolon, difficulty eating or drinking
The trypomastigote, as seen in the blood slide below, is the diagnostic and infectious stage. A CBC is collected and the hematology laboratory and pathologists observe for the trypomastigotes, which are diagnostic for this disease.
plasmodium spp-malaria
Sporozoa Key Terminology:
- Accole': around the outer edges or rim
- Agglutination: clumping of red blood cells, leading to infarcts
- Apicomplexa: phylum containing protozoans with a life cycle consisting of trophozoites, schizogony, gametogony, and sporogony
- Blackwater Fever: malarial complication that occurs when red blood cells rapidly hemolyse and burst, blocking capillaries, releasing hemoglobin, and resulting in the blockage of organs, leading to hematuria and kidney failure
- Bradyzoites: T. gondii trophozoites that slowly multiply inside tissue cysts in immune hosts; also found in sarcocysts
- Cryptozoite: the exoerythrocytic or tissue stage of malaria in which the Plasmodium spp develop in liver cells from sporozoites
- Reproduce intracellularly via asexual reproduction
- Produce many merozoites
- Exoerythrocytic cycle
- Completes in 1-2 weeks
- Gametes: the sex cells (male and female sperm and ova)
- Microgametocytes: male
- Macrogametocytes: female
- Develop from some of the merozoites to begin the sexual cycle in the definitive host mosquito
- Unite in the mosquito's stomach, where they form a motile zygote
- Gametocyte: sex cell that produces gametes
- Gametogony: phase in the life cycle of Plasmodium spp in which the male and female gametocytes are formed
- Hemolysis: rupture of red blood cells
- Hepatosplenomegaly: enlarged liver and spleen
- Hypnozoites: long-lasting schizonts of P. vivax and P. ovale that become modified and cause relapses of malaria
- Hemozoin: malarial pigment that contains iron, which builds up and accumulates in cells as cytoplasmic granules when the malaria parasites break down the hemoglobin
- Malaria: illness caused by the Plasmodium spp
- Macrogametocytes: Later in the infection, some merozoites develop into these female sex cells
- Maurer's Dots: 3 or more groups of protein antigens found on the surface of red blood cells infected with Plasmodium spp; when stained by Giemsa or Wright stain, they are dark blue, comma-shaped dots
- Merogony: this cycle occurs in the intestinal epithelium, and results in asexual multiplication of coccidians
- Merozoites: These are the mature trophozoites released from the red blood cells when they burst open at maturity during the asexual life cycle of malaria
- Exit the liver cells
- Invade nearby circulating red blood cells and become trophozoites (ring forms)
- Microgametocytes: some merozoites, later in the infection, develop into these male sex cells
- Necrosis: tissue death
- Nosocomial: hospital-acquired infection
- Oocyst: ookinete that encysts in the stomach wall of the mosquito infected with malaria
- Contains many infective sporozoites
- Sporozoites are released and migrate to the salivary glands, where they are transmitted during the bite for a blood meal
- Ookinete: motile zygote that is formed by the microgamete (male) and macrogamete (female) during fertilization; it encysts into an ookinete
- Parasitemia: % of parasites in the blood
- Paroxysm: malaria fever-chills syndrome
- Fever spikes when rbc's burst and release merozoites, releasing toxins (high fever lasting 2-6 hours)
- Shaking chills occurs when schizonts form (lasts 10-15 min.)
- Occurs every 36-72 hours
- Begins suddenly
- Followed by profuse sweating as the temperature lowers and comes back down to normal
- Immune resposne to parasitic antigens
- Patent: clinical signs and symptoms are evident
- Plasmodium species: the parasite carried by the definitive host (mosquito) that is infective to humans. There are at least 5 types infective to humans:
- P. falciparum
- Most deadly
- Cycles every 36-48 hours
- Cause changes to the surface membrane of the host red blood cells, causing agglutination (clumping) and hemolysis (bursting)
- Blocks the capillaries of the bloodstream, brain, liver, kidneys, heart, visceral organs, placenta, leading to infarction and tissue death (necrosis)
- Malignant tertian malaria
- Able to infect ALL stages of red blood cells
- Causes blackwater fever due to capillary blockage of ruptured red blood cells, hematozoin malarial pigment, hematuria, nephrotic syndrome and kidney failure
- Causes hepatosplenomegaly
- Can cause coma and death
- P. malariae
- Least deadly form
- Mildest form or benign disease
- Lowest parasitemia
- Cycles every 72 hours
- Merozoites only infect older, more mature red blood cells
- Quartan malaria
- P. vivax
- Benign tertian malaria
- Infects young, immature, large reticulocytes
- Cycles every 48 hours
- Can cause relapses
- Most widespread type of malaria
- Most prevalent type of malaria
- Forms some hypnozoites in the liver
- P. ovale
- Ovale malaria
- Infects young, immature, large reticulocytes
- Cycles every 48 hours
- Disease is less severe than P. vivax
- Can cause relapses due to formation of hypnozoites in the liver
- P. knowlesi
- Emerging type in Asia (Malaysia)
- Transmitted from long-tailed and pig-tailed macaques to humans by mosquitoes
- Can result in very high parasitemia because it divides rapidly during 24 hour cycles, leading to hepatorenal syndromes
- P. falciparum
- Pseudocysts: cystlike structures with membranes; formed by the host following acute infection with T. gondii; granulomas formed to hide from the immune system
- Filled with bradyzoites
- May occur in the GI tract, brain or other tissues
- Infection may be latent and may flare-up later on
- Recrudescence: condition caused by malarial infection in which infected red blood cells and symptoms reappear again after a period of feeling better, meaning that there was an insufficient immune response by the host or else they didn't respond well to treatment
- Relapse: reoccurance of malarial symptoms or a reactivation of the parasites from liver merozoites that start up a new cycle in red blood cells
- P. vivax
- P. ovale
- Reticulocytes: large, immature red blood cells
- P. vivax
- P. ovale
- P. falciparum (infects ALL stages)
- Sarcocyst: infective; contains banana-shaped bradyzoites
- P. falciparum
- Schizogony: merogony; asexual multiplication of apicomplexa; nuclear division occuring multiple times inside the cells prior to cytoplasmic division
- This is the process of the invasion of merozoites of red blood cells from ruptured schizonts, which continuously repeats
- This process causes the symptoms (fever-chills syndrome)
- This is known as the erythrocytic cycle
- Schizont: in the human red blood cell, this stage is developed and occurs from asexual multiplication of sporozoa
- Matures from merozoites in 36-72 hours
- Each one produces 6-24 NEW merozoites
- When mature, the RBC ruptures, releasing the merozoites, which invade new RBC's
- Schuffner's Dots: Named for Wilhelm Schuffner, who discovered them in 1904, these are red-staining dots in the reticulocytes infected with P. vivax or P. ovale, due to iron pigments, stained with Giemsa or Wright's stain, indicative of the changes caused to the infected RBC by the parasite
- Spore: infective for the definitive host once it is ingested or injected by an arthropod vector
- Sporocyst: fertilized oocyst; sporozoites have developed (Plasmodium spp)
- Sporogony: sexual reproduction of Apicomplexa; spores and sporozoites are produced here
- The sexual cycle
- Begins when the mosquito (definitive host) takes a blood meal and ingests gametocytes from an infected individual
- Sporoplasm: protoplasm that is infective; gel-like cytoplasm containing dissolved ions, lipids, amino acids, proteins, nucleic acids, monosaccharides
- Sporozoans: obligate endoparasitic protozoans; nonmotile other than gliding
- Most have a 2-host life cycle
- Sexual production
- Asexual reproduction
- Sporozoites: these develop inside the salivary glands of the mosquito, and are the stage that is transmitted to humans during the blood meal; develop inside a sporocyst
- Enter the cutaneous blood vessels, where they are carried to the liver cells and become cryptozoites
- This is the infective stage
- Tachyzoites: trophozoites quickly growing inside the cells infected with T. gondii
- Toxoplasmosis: infection caused by Toxoplasma spp
- Trophozoites: In Plasmodium spp, this is the "ring form", which mature into schizonts
- Zygote: fertilized cell formed by the union of the male and female gametes in the stomach of the definitive host mosquito
- Motile
- Also called the ookinete
- Moves through the mosquito's stomach wall and encysts as an oocyst
Schuffner's Dots:
Malaria Life cycle:
plasmodium vivax-most common malaria; tertian malaria
Plasmodium vivax is the causative agent of vivax or benign tertian malaria. It has worldwide distribution but is mainly found in temperate climates and in the tropics, especially in West Africa and north and south of the equator. Because there is an exoerythrocytic cycle as well as erythrocytic cycle, and because some hemozoites are formed in liver cells, relapses are common over a period of many years. The erythrocytic cycle is 44-48 hours. Merozoites show a preference for the invasion of immature red blood cells (reticulocytes).
The incubation period ranges from 10-17 days but there may be a prolonged initial incubation period of up to nearly a year! It is difficult to differentiate this species from P. ovale. Both species may exhibit Schuffner's dots or stippling. They stain red and are visibl between 15-20 hours after infection. The trophozite is amoeboid and the ring forms of this species may not form a complete circle, rather they may make a "comma" form, "exclamation point" form or simply look like interrupted signet rings. The trophozoites have a large, single ring, taking up about 1/3rd of the diameter of the RBC.
The incubation period ranges from 10-17 days but there may be a prolonged initial incubation period of up to nearly a year! It is difficult to differentiate this species from P. ovale. Both species may exhibit Schuffner's dots or stippling. They stain red and are visibl between 15-20 hours after infection. The trophozite is amoeboid and the ring forms of this species may not form a complete circle, rather they may make a "comma" form, "exclamation point" form or simply look like interrupted signet rings. The trophozoites have a large, single ring, taking up about 1/3rd of the diameter of the RBC.
plasmodium ovale-ovale malaria
Plasmodium ovale merozoites prefer to infect immature red blood cells (reticulocytes), therefore, infected RBCs are bigger and larger than the surrounding RBCs. This type causes ovale malaria and occurs primarily in tropical Africa, New Guinea and the Philippines, and a few sparse cases in Southeast Asia. In West Africa, it is way more prevalent than P. vivax. The incubation period is 10-16 days but longer periods of latency may occur prior to the primary attack. With this type, there is a persistence of exoerythrocytic bodies, therefore, relapses may occur over several years. The erythrocytic cycle is 48 hours.
Of all the malarias, this is most difficult type to diagnose. Its morphology is similar to P. vivax and has some similarities to P. malariae. Infected RBCs are enlarged and contain large, red-staining granules called Schuffner's dots or stippling. Oval, frequently fimbriated cells are common in this type, up to 60-70% of infected RBCs. Trophozoites form "basket-shaped" ring forms, and this type has band forms as well. These take up about 1/3rd the diameter of the RBC. The schizont contains 12-24 merozoites. The gametocyte is round.
Of all the malarias, this is most difficult type to diagnose. Its morphology is similar to P. vivax and has some similarities to P. malariae. Infected RBCs are enlarged and contain large, red-staining granules called Schuffner's dots or stippling. Oval, frequently fimbriated cells are common in this type, up to 60-70% of infected RBCs. Trophozoites form "basket-shaped" ring forms, and this type has band forms as well. These take up about 1/3rd the diameter of the RBC. The schizont contains 12-24 merozoites. The gametocyte is round.
plasmodium malariae-quartan malaria
Plasmodium malariae merozoites prefer to infect mature RBCs (erythrocytes) and causes a quartan malaria. This type is found in the tropics and subtropics of Africa, India, Burma, Sri Lanka, Malaysia, and Indonesia. It has a much lower prevalence than P. vivax or P. falciparum.
The incubation period ranges from 28-69 days and studies indicate that there is no persistence of exoerythrocytic bodies in the liver, therefore, no relapses with this type, however, this type may persist for many years, even up to 30 years. Because infection may be chronic, it may result in nephrotic syndrome, associated with damage to the kidneys. The erythrocytic cycle is 72 hours. Parasitemias in this type of infection are typically lower than the other types.
The trophozoite form as a single, distinct ring form resembling a signet ring. During early schizogony, there are also band forms. The schizont stage as about 6-12 merozoites. Gametocytes are oval-shaped.
The incubation period ranges from 28-69 days and studies indicate that there is no persistence of exoerythrocytic bodies in the liver, therefore, no relapses with this type, however, this type may persist for many years, even up to 30 years. Because infection may be chronic, it may result in nephrotic syndrome, associated with damage to the kidneys. The erythrocytic cycle is 72 hours. Parasitemias in this type of infection are typically lower than the other types.
The trophozoite form as a single, distinct ring form resembling a signet ring. During early schizogony, there are also band forms. The schizont stage as about 6-12 merozoites. Gametocytes are oval-shaped.
plasmodium falciparum-most severe, most deadly; malignant malaria
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Plasmodium falciparum is a sporozoan parasite that causes the most severe, most deadly, pathogenic form of malaria. It causes malignant tertian malaria and may cause an acute, fulminating course of infection. Death may occur very quickly if immediate treatment is not given. It invades ALL stages of red blood cells (merozoites). The ring stages and gametocytes are usually only found in the RBCs of the peripheral circulation, whereas the growing trophozoites and schizonts may be found in the visceral bloodstream but not in the peripheral circulation unless the parasitemia is high. For this reason, it ruptures the RBC's, causing hemolysis, hematuria, and kidney failure, known as "blackwater fever". The ruptured RBC's can clog up blood vessels, mainly capillaries, resulting in kidney failure. This can result in coma and death.
The incubation period for infection ranges from 8-20 days. Because there is no persistence of exoerythrocytic bodies in the liver, relapses typically do not occur. Quick and accurate diagnosis of infection is of utmost importance.
The trophozoite ring forms are small and look like signet rings. There are often multiple rings in one RBC. RBC's often have vacuoles. The gametocytes are unique because they are crescent or banana-shaped. The mature trophozoites and schizonts often have Maurer's dots.
The incubation period for infection ranges from 8-20 days. Because there is no persistence of exoerythrocytic bodies in the liver, relapses typically do not occur. Quick and accurate diagnosis of infection is of utmost importance.
The trophozoite ring forms are small and look like signet rings. There are often multiple rings in one RBC. RBC's often have vacuoles. The gametocytes are unique because they are crescent or banana-shaped. The mature trophozoites and schizonts often have Maurer's dots.
babesia microti-babesiosis
Babesia microti is a parasite carried by ticks. Infection occurs via tick bites. Symptoms include fever, shaking, chills, fatigue and resemble malaria. Diagnosis is made by the presence of trophozoites in the peripheral blood smear, and should not be confused with malarial parasites, which look very similar.
Recently, in the USA, in SC, Asian longhorned ticks, an invasive species, have been discovered, and are being tracked by DHEC as of July, 2022. They were found infesting a cattle farm in York county, and were first spotted in 2010. In addition to SC, they have been spotted in 16 other states. In 2020, they were found on shelter dogs in 2 other SC counties. Though rare and uncommon, their bites can cause babesiosis in humans and animals, including livestock. These ticks, as well as Ixodes dammiti, also carry the parasites that cause Lyme Disease, Rocky Mountain Spotted Tick Fever & Anaplasmosis. A person can be coinfected with one or more of these diseases simultaneously.
A single female tick has the ability to lay up to 2,000 eggs! This means that just one tick has the ability to create thousands of other ticks that could potentially carry disease. The tick is small and brown. They are most often found on livestock, including cattle and sheep, however, they can also feed on dogs and humans as well.
The parasite mainly carried by these ticks is known as Theileria. Illnesses are zoonotic and are vector-borne. The ticks known as Ixodes scapularis, or deer ticks (also known as bear ticks or black-legged ticks), are typically the types of ticks that carry Borrelia burgdorferi, which causes Lyme Disease, Babesia microti, which causes babesiosis, Anaplasma, which causes anaplasmosis, Rickettsia rickettsii, which causes Rocky Mountain Spotted Fever, and Flavivirus, which causes Powassan virus disease.
These are hard-bodied ticks that are known to parasitize the white-tailed deer, mice, lizards, migratory birds, especially when in the larval and nymph stages, and are found from the midwestern USA to the southeastern USA. They can be as tiny as a pinhead when in the larval or nymph stages. The life cycle of this tick is 2-years, during which time it passes through a larval stage, takes a blood meal, matures into a nymph stage, takes a blood meal, and then matures into an adult. It cannot mature to the next stage without taking a blood meal. The female latches onto its host and feeds for 4-5 days. It takes about 36 hours for the bacteria or virus it is carrying to spread.The primary and preferred host is the white-tailed deer. Secondary hosts include mice and other rodents.
Once the female tick has finished her meal, she drops off and hibernates in leaf litter until the winter season is over. In the Spring, the deer tick lays anywhere from a few hundred to a few thousand eggs. Between the tick stages is when parasitization of the tick with the bacteria Borrelia burgdorferi, a spirochete that can cause Lyme Disease in humans, occurs. The tick is hardy, active after a frost, and can survive extremes. If she transmits the bacteria to humans, the incubation period is 1-2 weeks prior to the onset of symptoms.
The Ixodes scapularis tick is the main vector of Lyme Disease in North America. The CDC states that there are approximately 300,000 cases each year in the USA, and about 65,000 each year in Europe. Most cases occur during the late spring and early summer months, when people are traveling, hiking and fishing outdoors, and spending time in areas where the ticks may be endemic or hiding out. The nymph stage is the most common to infect humans, and they are very difficult to spot because of their minute size.
Humans infected with Lyme Disease can also simultaneously be coinfected with the bacteria causing babesiosis and anaplasmosis. In studies done on the ticks, more than half of them were found to carry at least one or more of the pathogens that cause these diseases. Diagnosis is based on blood tests, blood smears, and finding antibodies in the host's blood to the antigen of the bacteria, virus or parasite transmitted by the tick.
Lyme Disease was named for where it was first discovered, Lyme, Connecticut, in 1975. In 1981, the bacteria linked to the disease, Borrelia burgdorferi, was first described by Willy Burgdorfer, whom it was named after.
Prevention includes awareness, wearing hats, long sleeves and long pants when spending time outdoors, especially when hiking or fishing or hunting, wearing insect repellant containing DEET or picaridin, removing a tick carefully with sterilized tweezers. Treatment is typically a regime of doxycycline, amoxicillin, and/or cefuroxime for 2-3 weeks.
Symptoms:(*NOTE: These ticks can carry multiple pathogens and result in coinfections. Symptoms are similar.)
Lyme Disease:
- erythema migrans (spreading bull's eye rash or a rash that looks like a target)-about a week after a bite occurs in about 70-80% of cases
- fever
- headaches
- fatigue
- if uintreated, can lead to paralysis of the face
- joint pain
- severe headaches
- neck stiffness
- heart palpitations
- repeated episodes of joint pain and swelling months to years later, in about 10-20% of cases
- shooting pains
- tingling in arms or legs
- memory problems
- chronic fatigue syndrome
- fever
- headache
- rash a few days later (maculopapular, then petechial)
- small spots of bleeding (petechiae) that starts on the wrists and ankles and spreads
- muscle pain (myalgia)
- malaise
- nausea and vomiting
- chills
- abdominal pain
- joint pain
- conjunctivitis
- forgetfulness
- complications may include hearing loss or blindness
- complications may include sepsis, resulting in necrosis and limb loss or death (0.5%)
- carried by the bacteria Rickettsia rickettsii
- vector: American Dog Ticks, Rocky Mountain Wood Ticks, Brown Dog Ticks
- transmission: rarely, blood transfusion
- treatment: doxycycline
- annual cases: <5,000 in the USA (June, July)
Babesiosis:
- malaria-like parasite disease caused by Babesia microti or other Babesia spp, or Theileria spp
- may be asymptomatic
- fever
- hemolytic anemia
- malaria-like symptoms
- chills
- sweats
- fever
- joint pain
- malaise
- nausea
- vomiting
- muscle pain
- thrombocytopenia
- 1-4 weeks after bite
- loss of appetite
- sore throat
- cough
- conjunctivitis
- photophobia
- weight loss
- emotional lability
- depression
- hyperesthesia
- enlarged liver, spleen
- jaundice
- retinopathy
- retinal infarcts
- neutropenia
- sepsis
- organ failure
Anaplasmosis:
- tickborne disease caused by the bacteria Anaplasma, which cause anaplasmosis, and infect red blood cells
- jaundice
- weight loss
- loss of appetite
- diarrhea
- pale skin
- high fever
- aggressive behavior
- leukopenia
- thrombocytopenia
- elevated liver enzymes
- erythema migrans rash
- severe anemia
- heart palpitations
- blood in the urine
- diarrhea
Ehrlichiosis:
- tickborne disease caused by the bacteria Ehrlichia spp, a type of Rickettsial bacteria, transmitted by the same ticks that carry the other tickborne diseases
- infects white blood cells
- zoonotic
- ehrlichiosis
- headache or severe headache
- muscle aches
- chills
- shaking
- nausea
- vomiting
- weight loss
- loss of appetite
- abdominal pain
- diarrhea
- cough
- joint pain
- photophobia
- weakness
- fatigue
- problems with memory
- confusion
- temporary loss of basic motor skills
- possible rash (10% of cases)
- complications can cause respiratory failure, organ failure
- secondary infections
other types of parasites:
toxocara spp-visceral larval migrans
Toxocara is a nematode that causes visceral larva migrans. It is found worldwide, but is most common in warm, moist regions of the world. The larval stage occurs in human tissues, particularly in the liver, eye and central nervous system. Adult worms in animal hosts live in the small intestine. Adult male worms measure 4-6 cm in length, and females measure 6.5-10.0 cm in length.
Humans, particularly toddler-aged children, become infected via the ingestion of infective eggs, which can occur on contaminated toys, litter boxes, pet food and water. The larvae become encapsulated in the organs and tissues of the body. They are able to live for a long period of time. Rarely, the parasite may infect adult humans as well.
Canine or feline infection is diagnosed by finding eggs in stool samples. Human infections are diagnosed by clinical symptoms and the findings of larvae in tissue and organs.
Humans, particularly toddler-aged children, become infected via the ingestion of infective eggs, which can occur on contaminated toys, litter boxes, pet food and water. The larvae become encapsulated in the organs and tissues of the body. They are able to live for a long period of time. Rarely, the parasite may infect adult humans as well.
Canine or feline infection is diagnosed by finding eggs in stool samples. Human infections are diagnosed by clinical symptoms and the findings of larvae in tissue and organs.
toxoplasma spp-toxoplasmosis
Infection occurs via ingestion of oocysts, trophozoites or pseudocysts in undercooked meat or through fecal-oral route
isospora belli-diarrhea
Coccidiosis, or isosporiasis, occurs in the intestinal tract of humans. The eggs measure 20-33 microns by 10-19 microns, and are unsporulated when they pass in the stool. The oocysts are ovoid in shape, slightly taper at the ends, and have a double-layered, smooth, hyaline wall. Unsporulated cysts develop in the soil and contain 2 sporulated sporocysts in the infective stage. In the intestinal mucosa, sexual reproduction occurs and oocysts are produced and then passed in the stool. Because the passage of oocysts is short and sporadic, they may be easily overlooked in fecal examinations. The best chances of recovery are to examine multiple stool specimens.
cryptosporidium-
Cryptosporidium oocysts in a fecal wet mount are observed here. Oocysts are spherical to slightly oval and measure 4-5 microns in width. Oocysts are very refractile and contain several fine-to-prominent dark granules. They are infective, sporulated, and contain 4 sporozoites upon passage in the stool. Phase-contrast microscopy aids in the visualization of these oocysts in wet mount preparations.
Cryptosporidium spp coccidioides are able to infect birds, reptiles, mammals, and humans. Though infections mostly affect immunologically compromised or impaired individuals, infections can also occur among healthy individuals as well. It is a zoonosis, and reservoirs may include cows, pigs, sheep, rodents, chickens, pigeons, other mammals, and other birds. Cryptosporidiosis infections are characterized by chronic, profuse, watery diarrhea, dehydration, and even death, particularly in immunocompromised individuals.
cyclospora-cyclosporidasis
artifacts:
Yeast
Pollen
Diatoms
plant fiber/plant hair/plant cell/plant material:
Charcot-Leyden Crystals
Charcot-Leyden crystals are observed here in a wet mount for microscopic O & P evaluation. CL crystals are breakdown products of eosinophils. They may be seen in feces or in sputum, and are 6-sided crystals that may occur in individuals who are either parasitized or experiencing other infections or allergies eliciting and immune response.
Eosinophilia
Giant platelets
Specific laboratory testing for parasitology:
Biofire (filmarray) gi panel pcr:
This multiplex PCR panel tests for bacteria, viruses and parasites in the stool. The stool tested must be in Cary-Blair preservative. It takes about 1 and 1/2 hours to complete. The FILMARRAY is an FDA-cleared multiplex PCR system that integrates sample preparation, amplification, detection and analysis. It requires just a few minutes of hands-on-time (about 2 minutes of prep time). The four parasites the panel tests for include:
https://www.biofiredx.com/products/solutions/for-labs/
- Cyclospora cayatenensis
- Cryptosporidium
- Giardia lamblia
- Entamoeba histolytica
https://www.biofiredx.com/products/solutions/for-labs/
glcs rapid assay (eia) for giardia-cryptosporidium testing:
"Crypto Giardia Rapid Test is a rapid immunoassay for the qualitative detection of Cryptosporidium parvum and Giardia lamblia specific antigens in aqueous extracts of human fecal specimens.
* 95% confidence interval
** According to the American Society for Microbiology at asm.org."
How to perform the test:
- Simplified procedure, results in less than 30 minutes
- Less than 10 minutes of hands-on-time required
- Sensitivity is 100% for both Giardia and Crypto (as compared to microscopy)*
- Eligible for dual reimbursement**
* 95% confidence interval
** According to the American Society for Microbiology at asm.org."
How to perform the test:
- Take out the reagents and kit and let them come to room temp.
- Place one of the falcon tubes that comes with the kit into the stand that comes with the kit.
- Label the tube and 1 cartridge and match up the patient sample.
- Place 2 drops of diluent (white top) into the tube.
- Add 60 microliters of patient stool in Cary-Blair with the provided pipette (to 2nd line) into the tube.
- Add 2 drops Conjugate A (red top)
- Add 2 drops Conjugate B (gray top)
- Mix
- Pour the entire tube contents into the sample test well in the provided cartridge.
- Set the timer for 10 minutes and read and record your results.
- Results are invalid after 15 minutes.
modified-acid fast stain for cryptosporidium and for cyclospora cayatenensis:
correlation tests: fecal lactoferrin (leukocytes) and stool occult blood
The fecal lactoferrin (fecal leukocytes) test is a rapid immunoassay that identifies if white blood cells are present in the stool, which can indicate inflammation or infection. Inflammatory diarrhea can be due to bacterial, viral, or parasite infection, rarely yeast overgrowth, or to a sensitivity, such as gluten intolerance. It can also be linked to irritable bowel syndrome, malabsorption syndrome, food allergy, ulcerative colitis or Crohn's disease flareups.
Fecal leukocytes are commonly seen in active infections caused by bacteria, including Shigella, Salmonella, E. coli 0157:H7, Campylobacter, Clostridiodes difficile, or others.
This test is typically ordered when a patient has many loose stools or watery stools, blood or mucous in the stools, severe abdominal cramping and pain, and fever. Other tests ordered typically include lactoferrin, calprotectin, GI panel, ova and parasites, toxin tests to look for C. difficile and Shiga toxins, stool culture, and hemoccult testing. Sometimes others, including H. pylori, and/or fecal fats to look for steatorrhea, or malabsorption, are also ordered.
Hidden blood in the stool, or that which isn't visible, is called "hemoccult" or "occult" blood. It can indicate infection, hemerrhoids, polyps, or something more serious, such as colorectal cancer. Certain foods and medications can interfere with this test, so at least 3 days prior to testing, it is recommended that individuals avoid taking vitamin C, iron, drinking tea, having a barium X-ray performed, avoid pain relievers (aspirin, Ibuprofin, Advil, Motrin, etc...), and avoid eating broccoli and turnips and red meat.
The immunochemical test on the bottom left image is more sensitive than the older, more traditional guaiac test (right side). It doesn't require the same dietary restrictions, and can often be used on a random stool sample. The guaiac test requires a set of 3 stool samples taken at random times, from multiple samples. The cards are then either mailed back into or taken back to the laboratory, whereas the immunochemical test requires that the stool sample be taken and sent to the lab for the lab to test.
If the occult blood test is positive, further testing is needed to investigate where the blood is coming from and the cause. This may include a colonoscopy, sigmoidoscopy, EGD, barium test, or other tests.
Fecal leukocytes are commonly seen in active infections caused by bacteria, including Shigella, Salmonella, E. coli 0157:H7, Campylobacter, Clostridiodes difficile, or others.
This test is typically ordered when a patient has many loose stools or watery stools, blood or mucous in the stools, severe abdominal cramping and pain, and fever. Other tests ordered typically include lactoferrin, calprotectin, GI panel, ova and parasites, toxin tests to look for C. difficile and Shiga toxins, stool culture, and hemoccult testing. Sometimes others, including H. pylori, and/or fecal fats to look for steatorrhea, or malabsorption, are also ordered.
Hidden blood in the stool, or that which isn't visible, is called "hemoccult" or "occult" blood. It can indicate infection, hemerrhoids, polyps, or something more serious, such as colorectal cancer. Certain foods and medications can interfere with this test, so at least 3 days prior to testing, it is recommended that individuals avoid taking vitamin C, iron, drinking tea, having a barium X-ray performed, avoid pain relievers (aspirin, Ibuprofin, Advil, Motrin, etc...), and avoid eating broccoli and turnips and red meat.
The immunochemical test on the bottom left image is more sensitive than the older, more traditional guaiac test (right side). It doesn't require the same dietary restrictions, and can often be used on a random stool sample. The guaiac test requires a set of 3 stool samples taken at random times, from multiple samples. The cards are then either mailed back into or taken back to the laboratory, whereas the immunochemical test requires that the stool sample be taken and sent to the lab for the lab to test.
If the occult blood test is positive, further testing is needed to investigate where the blood is coming from and the cause. This may include a colonoscopy, sigmoidoscopy, EGD, barium test, or other tests.
arthropods:
Important Terminology:
Disease Transmission:
- Arachnida: Class in the phylum Arthropoda
- Ticks
- Mites
- Spiders
- Scorpions
- Life cycle:
- Egg to adult via metamorphosis
- Incomplete (hemimetabolous)
- Egg
- Nymph (instar)
- Similar to the adult
- Molts a few times prior to adulthood via ecdysis
- Similar to the adult
- Imago (adult)
- Lice
- Bugs
- Arachnids
- Lice
- Egg
- Complete (holometabolous)
- Egg
- Larva (segmented, wormlike structure)
- Larval instars (several)
- Pupa
- Imago (adult)
- Flies
- Mosquitoes
- Fleas
- Most crustaceans
- Eggs
- Free-swimming nauplius larvae (several molts)
- Cypris larva
- Imago (adult)
- Eggs
- Flies
- Egg
- Incomplete (hemimetabolous)
- Egg to adult via metamorphosis
- Acarina: Order of Arachnida that includes mites and ticks
- Arthropoda: Phylum of arthropods
- Have a hard exoskeleton made of chitin
- Have paired, jointed legs
- Head is adapted for sensory functions and chewing or piercing
- Eyes: single lens or compound
- Systems: digestive, respiratory, nervous, excretory
- Body cavity (coelom) is present
- Filled with a fluid similar to blood
- Filled with a fluid similar to blood
- Largest Phylum, consisting of >80% of all animal life
- Directly transmit or cause >80% of all diseases
- Both beneficial and destructive
- Includes the invertebrates
- Five classes, 3 of which contain many of the medically significant arthropods:
- Insecta
- Arachnida
- Crustacea
- Insecta
- Have a hard exoskeleton made of chitin
- Capitulum: the mouth (oral) parts of ticks and mites
- Chitin: hard, supportive polysaccharide sugar that makes up the exoskeleton of arachnids
- Crustacea: Class in the phylum Arthropoda
- Crabs
- Lobsters
- Crayfish
- Crawfish
- Shrimp
- Water fleas
- Wood Lice
- Barnacles
- Crabs
- Ctenidia: on the head of fleas; comblike structures that aid in classification
- Genal Ctenidia: found above the mouth parts
- Pronotal Combs: behind the head
- Genal Ctenidia: found above the mouth parts
- Cypris: Larval resting stage
- Some crustaceans
- Metamorphosis occurs
- Similar to a pupa
- Some crustaceans
- Ecdysis: shedding or molting of an outer layer, followed by the development of a new one
- Entomology: Branch of zoology focusing on the study of insects
- Exoskeleton: hard shell made of chitin on the outside of the body
- Supportive
- Protective
- Supportive
- Imago: adult insect or arachnid
- Insecta: Class in the phylum Arthropoda containing insects
- Head
- Thorax
- Abdomen
- Head
- Instar: one of the nymph or larva stages in between molting/sheeding
- Invertebrates: animals without a spinal column
- Metamorphosis: transformation of shape or structure
- Transitional stage from one developmental stage to another
- Incomplete: nymphs look like adults
- Complete: larvae and pupae are distinct and different from adults
- Transitional stage from one developmental stage to another
- Myiasis: infestation of the body with fly larvae
- Nauplius: in the life cycle of the crustacean, this is the earliest larval stage
- Nymph: in the life cycle of various arthropods, this is a developmental stage that resembles an adult
- Pediculosis: lice infestation
- Pupa: resting stage between larva and impago
- A cocoon
- Encased
- A cocoon
- Scutum: a plate or shield made of chitin that covers part or all of the dorsal surface of hard ticks
- Temporary Host: an arthropod temporarily lives and feeds on the blood or tissue of this host
Disease Transmission:
- Mechanical Transfer:
- Passive
- Feces
- Contamined soil
- Contamine food
- Utensils
- Insect is not required as part of the parasite's life cycle
- Passive
- Biological Transfer:
- Insect is a vector/carrier
- Required for part of the parasite's life cycle
- Insects serve as intermediate or definitive hosts
- Inject the parasite into their new host or deposit them on the skin
- Some pass from the adult insect to its offspring in utero (transovarial transmission)
- Vertical transmission
- Bite or sting
- Insect is a vector/carrier
- Ectoparasites: affect the outside layers and feed on blood)
- Endoparasites: affect the inside organs
References:
- The Centers for Disease Control and Prevention: <https://www.cdc.gov/dpdx/az.html>
- Some Images: Courtesty of The Centers for Disease Control and Prevention, DPDX, Diagnostics, https://www.cdc.gov/dpdx/diagnosticprocedures/stool/morphcomp.html
- Many Images Courtesy of The Public Health Image Library, CDC, <https://phil.cdc.gov/>
- Wikimedia Commons, Public Domain Images
- Leventhal, R. Cheadle, R. Medical Parasitology: A Self-Instructional Text, 6th and 7th Editions, F.A. Davis Publishing, 2020.
- Reynolds, Jeanette (MS-Biology, M-ASCP, MT, AMT). Personal Clinical Lab, Teaching and Writing Experience: Landstuhl Regional Medical Center, Germany, 2007-2010; Penrose Hosp, 2010-2012; NAU 2010-2012; MAMC, Fort Carson, Colorado Springs, CO 2010-2012; Brook Army Medical Center in Association With Medical Education and Training Center, Fort Sam Houston, San Antonio, TX 2013-2014; Joint Base Lewis-McChord, Tacoma, WA 2015-2016; Pierce College, Tacoma, WA 2015-2016; El Paso Community College and DaVinci School for Science and the Arts, TX, 2016-2017; Prisma Health 2017-2019; Lexington Medical Center 2014 and 2019-Present/Current; On Course Learning (CE Modules) 2016-Present; APass Education Writing (CE Modules/Test Questions) 2016-Present; Lexington Medical Center Microbiology, 2020-present, Southwestern Community College, 2022-present
- Cooper, Nancy (MLS-ASCP), Madigan Army Medical Center, Joint Base Lewis-McChord, Tacoma, WA (Parasitology).