Nematodes Flashcards
Describe the morphology of a nematode:
What is it’s common name?
Nematodes are commonly called "roundworms". They are: round when viewed in-cross section unsegmented comprised of both sexes Notable Features (not universal): lips, teeth/hooks rhabditiform & filariform larvae buccal cavity esophagus genital primordium
What is the scientific name of:
Pinworm / Seatworm
Enterobius vermicularis
What is the scientific name of:
Whipworm
Trichuris trichiura
What is the scientific name of:
Large intestinal roundworm
Ascaris lumbricoides
What is the scientific name of:
New World Hookworm
Necator americanus
What is the scientific name of:
Old World Hookworm
Ancylostoma duodenale
What is the scientific name of:
Threadworm
Strongyloides stercoralis
What is the scientific name of:
Trichina worm
Trichinella spiralis
How is this organism diagnosed?
(diagnostic stage/symptoms)
Enterobius vermicularis:
Eggs are diagnostic.
Eggs are located on perianal skin and found by cellophane test.
Adult is also diagnostic but less common and unnecessary.
Symptoms: itching
How is this organism diagnosed?
(diagnostic stage)
Trichuris trichuria:
Eggs are diagnostic and found in feces.
Symptoms: Slight infection asymptomatic Heavy burden- loose stool with blood &/or mucus weight loss/weakness abdominal pain and tenderness/colitis rectal prolapse (esp. in children)
How is this organism diagnosed?
(diagnostic stage)
Ascaris lumbricoides
Can be diagnosed by exit of migrating adult through nose, mouth or anus. (ew)
Eggs are diagnostic when present in feces:
May be fertilized &/or nonfertilized.
Can be asymptomatic.
Many symptoms come from migration of adults (moving):
vomiting, pain, obstructions, tangling & bile duct complications
How is this organism diagnosed?
(diagnostic stage)
Trichinella spiralis
Encysted larvae in striated muscle is diagnostic:
found by biopsy or inspection of suspicious meat (bear, pork, wild boar)
How is this organism diagnosed?
(diagnostic stage)
Necator americanus
Egg in fresh or preserved feces:
NOTE: species cannot be differentiated by egg alone
report as “Hookworm ova”
Possible for appearance of rhabditiform larvae in fresh sample- Differentiate from Strongyloides by longer buccal cavity and lack of prominent genital primordium
How is this organism diagnosed?
(diagnostic stage)
Ancylostoma duodenale
Egg in fresh or preserved feces:
NOTE: species cannot be differentiated by egg alone
report as “Hookworm ova”
Possible for appearance of rhabditiform larvae in fresh sample- Differentiate from Strongyloides by longer buccal cavity and lack of prominent genital primordium
How is this organism diagnosed?
(diagnostic stage)
Strongyloides stercoralis
Rhabditiform larvae passed in feces
(eggs hatch in mucosa of small intestine)
Larvae is diagnostic and may resemble hookworm rhabditiform.
Strongyloides larvae has VERY short buccal canal and prominent genital primordium.
