ICL 3.3: Nematodes Flashcards
what’s the common name for nematodes?
roundworms
what are the two groups of nematodes?
- intestinal nematodes
2. tissue nematodes
what are intestinal nematodes?
adults live in GI tract, maturing usually in small intestine or colon
some species get to intestine after larval migration via internal organs (e.g. lung)
usually direct infection by eggs or larvae
almost all have direct life cycle needing humans
what are tissue nematodes?
adults live in lymphatics or in subcutaneous tissues – release larvae
arthropod vectors needed for transmission of infection (i.e. indirect life cycle with human as definitive host)
which nematodes are transmitted by ingestion and cause intestinal infection?
- A. lumbriocoides
- E. vermicularis
- T. trichiura
which nematodes are transmitted by ingestion and cause tissue infection?
- T. spiralis
2. D. medinensis
which nematodes are transmitted by contact and cause intestinal infection?
- S. stercoralis
- A. duodenale
- N. americanus
which nematodes are transmitted by bite and cause tissue infection?
- O. volvulus
2. W. bancrofti
which nematodes are transmitted by ingestion and cause tissue infection in the wrong host?
- toxocara cani
- toxocara cati
- anisakis simplex
which nematodes are transmitted by contact and cause tissue infection in the wrong host?
- A. caninum
2. A. braziliensis
what’s the common name for enterobius vermicularis?
pinworm
transmitted by ingestion –? intestinal infection
what is the life cycle of enterobius vermicularis?
- direct life cycle
1. eggs on perianal folds; larvae inside the eggs mature within 4-6 hours
2. embryonated eggs are ingested by humans
3. larvae hatch in small intestine
4. adults in lumen of colon
5. gravid female migrates to perianal region at night to lay eggs
what age group is often infected with enterobius vermicularis?
children
it’s found
infections more frequent in school- or preschool-children and in crowded conditions
where in the world are enterobius vermicularis infections more common?
worldwide
enterobiasis appears to be more common in temperate than tropical countries
what is the most common helminthic infection in the united states?
enterobius vermicularis
what are the symptoms of enterobius vermicularis infection?
enterobiasis is frequently asymptomatic
perianal pruritus (itch), especially at night
this may lead to excoriations and bacterial superinfection
includes anorexia, irritability, and abdominal pain
occasionally, there’s invasion of the female genital tract with vulvovaginitis
how do diagnose enterobius vermicularis infection?
eggs on anal skin
you can detect them using clear sticky tape = scotch tape test
sometimes the worms are also seen in feces –> look like a grain of rice with a clear outer membrane and then speckled inside
how do you treat enterobius vermicularis infection?
pyrantel pamoate
what’s the common name for trichuris trichiura?
whipworm
they literally look like a whip
transmitted by ingestion –> intestinal infection
where are trichuris trichiura found in the body?
they live in the cecum and ascending colon
the adult worms are FIXED in that location
how long does it take for trichuris trichiura to become infectious?
eggs take ~3-4 weeks to become infectious (embryonate)
best in warm conditions and sandy soils
females survive 1-2 years
how do you get a trichuris trichiura infection?
by ingesting embryonated eggs
it takes eggs 3-4 weeks to become infectious/embryonate
you also often be co-infected with hookworm and Ascaris
what’s the life cycle of trichuris trichiura?
- unembryonated eggs passed in feces
- 2-cell stage
- advanced cleavage
- embryonated eggs are ingested by humans
- larvae hatch in small intestine
- adults in cecum
where in the world are trichuris trichiura found?
worldwide
infections more frequent in areas with tropical weather and poor sanitation practices, and among children
trichuriasis occurs in the southern United States.