Nematodes And Microfilariae Flashcards
NEMATODES
- Round worms.
- large size and cylindric, unsegmented bodies.
- Primarily live in intestinal tract and ID the eggs in feces.
- Transmitted by mosquitoes or biting flies.
- Most produce larval worms called microfilariae in blood specimens or in subcutaneous tissues and skin snips.
Enterobius vermicularis
(pinworm)
- Crowded conditions
(day-care centers, schools, and mental institutions).
- Most common helminthic infection in North America.
- Eggs are ingested Autoinfection (“retrofection”) can occur.
- Food handlers.
- No known animal reservoir.
- pruritus, loss of sleep, and fatigue.
- characteristic eggs on the anal mucosa. (Scotch tape prep. )
Ascaris lumbricoides
(pink worms)
- Poor sanitation and where human feces is used as fertilizer.
- survive extreme temperatures and persist for months in sewage.
- Most common helminthic infection worldwide.
- No animal reservoir.
- Ingestion of eggs.
- could migrate into the bile duct and liver and perforate the intestine.
- Worms can migrate in response to fever, drugs other than those used to treat ascariasis.
- Heavy infection : Pneumonitis.
- Avoid human feces.
Toxocara and Baylisascaris
- infected dogs/cats/raccoons.
- Especially children.
- exposure to contaminated feces.
- Symptoms of VLM, NLM, and OLM are related to location.
- eosinophilic granulomas, and necrosis. lungs, heart, kidneys, liver, skeletal muscles, eyes, and central nervous system (CNS).
- known exposure to dogs, cats, or raccoons.
Trichuris trichiuria
(whip worm)
[trichuriasis]
- poor sanitation and the use of human feces as fertilizer.
- Exposure to contaminated feces.
- worms penetrate deep into the intestinal mucosa.
- abdominal pain and distention, bloody diarrhea, weakness, and weight loss.
- Appendicitis.
- prolapse of the rectum is seen in children.
- characteristic bile-stained eggs with polar Light infestations, may find few eggs in the stool.
Ancylostoma duodenale AND Necator americanus
(old and new world hook worm)
[hookworm infection]
- feces in deposited good soil like the southern parts of the United States.
- Direct contact with contaminated soil (barefoot).
- Rash at sites of entry, pneumonitis. nausea, vomiting, and diarrhea.
- Severe cases: emaciation, mental and physical retardation.
- Wear shoes!
Ancylostoma Braziliense
(Dog or cat hook worm)
[cutaneous larva migrans]
- naturally parasitic in the intestines of dogs and cats.
- cutaneous larva migrans that also is called ground itch and creeping eruption.
- penetrate intact skin but can develop no further in humans.
- The larvae remain trapped in the skin creating serpentine tunnels.
- Children playing with soil or sandboxes contaminated with animal feces.
- cause erythematous and vesicular reaction.
- Pruritus and scratching.
- half of patients develop transient pulmonary infiltrates with peripheral eosinophilia (Löffler syndrome).
Strongyloides stercoralis
(thread worm)
[Strongyloidiasis]
- Animal reservoirs, such as domestic pets.
- Sexual transmission also occurs.
- Pneumonitis.
- Intestinal infection is usually asymptomatic.
- Heavy burden can affect the biliary and pancreatic ducts, small bowel, and colon, causing inflammation and ulceration leading to epigastric pain and tenderness.
- Mimic peptic ulcer disease + peripheral eosinophilia…think strongyloidiasis.
- three stools, one per day for 3 days larvae may occur in “showers,” with many present one day and few or none the next.
Trichinella spiralis
[trichinosis]
(Pork Worm)
- eating improperly cooked pork .
- Polar bears/walruses can be infected with T. spiralis (T. nativa ) (resistant to freezing).
<10 larvae per gram of tissue; asymptomatic or flu-like, slight fever, diahhrea).
> 100 generally have significant disease
> 1000 to 5000 have a very serious course that occasionally ends in death.
- Persistent fever, gastrointestinal distress,marked eosinophilia, muscle pain, and periorbital edema occur.
- “Splinter” hemorrhages beneath the nails
Microfilariae
identification of microfilarriae is based on the presence of a sheath covering the larvae, as well as the distribution of nuclei in the tail region
Wuchereria Bancrofti
(Bancroft filaria)
[Filariasis]
- tropical and subtropical areas with no known animal reservoir.
-infected mosquito,
- Acute lymphangitis and lymphadenitis with fever/chills.
- Later, enlarged lymph nodes, extremities, the scrotum, and the testes, with occasional abscess, elephantiasis.
Brígida malayi
(Malayan filaria)
[Filariasis]
- n Malaysia, India, Thailand, Vietnam, and parts of China, Korea, Japan, and many Pacific islands.
- Animal reservoirs (cats and monkeys).
- infected mosquito,
- Acute lymphangitis and lymphadenitis with fever/chills.
- Later, enlarged lymph nodes, extremities, the scrotum, and the testes, with occasional abscess, elephantiasis.
Loa Loa
(African Eye worm )
[ Loiasis]
- rain forests of Africa, bite of infected Chrysops (the mango fly).
- Asymptomatic for ~12 months..
- Calabar swellings in extremities (painful and pruritic).
- May also migrate to eyelids, and impaired vision.
- present during the daytime10-AM-2PM.
- induce severe allergic reactions that require treatment with corticosteroids.
Mansonella perstans
[Filariasis]
- no known reservoir.
- Biting midges and black flys.
- Generally asymptomatic.
- rarely, lymphatic obstruction resulting in elephantiasis.
- nonsheathed microfilariae in blood.
- allergic skin reactions, edema, and Calabar swellings.
- Diagnostic: blood smear.
Mansonella streptocerca
[Filariasis]
- Africa, especially in the Congo basin.
- Monkeys serve as reservoir hosts.
- Biting midges and black flys,
- Generally asymptomatic.
- Diagnostic blood smear.
