MLT GlobeParasitology: Nematodes (roundworms)
66 Parasitology MCQs on Nematodes (roundworms) with answers and explanations.
Which intestinal nematode usually does NOT release its eggs into the bowel lumen, so eggs are rarely found in routine stool examination?
Gravid Enterobius females migrate out of the anus and lay eggs on perianal skin, so stool tests are poor. Ascaris and hookworm eggs are shed in faeces, and T. saginata is a cestode, not a nematode.
A 4-year-old wakes at night scratching his perianal area. Which laboratory approach will best confirm the suspected infection?
Enterobius eggs are laid on perianal skin, so a morning cellophane-tape (Graham) test before washing is the method of choice. Stool tests miss most cases and serology is not used.
Chronic heavy hookworm infection in a child most typically leads to which laboratory finding?
Adult hookworms suck blood from the intestinal mucosa, causing chronic iron loss and microcytic anaemia. B12-deficiency macrocytosis is linked to Diphyllobothrium, not hookworm.
In which specimen are rhabditiform larvae of Strongyloides stercoralis usually detected?
Strongyloides eggs hatch in the intestinal mucosa, so rhabditiform larvae (not eggs) are passed in faeces; agar plate culture or Baermann improves detection. Larvae appear in sputum only in hyperinfection.
Microscopy of stool shows brown, barrel-shaped eggs with a clear plug at each pole. Which infection is diagnosed?
Whipworm eggs are barrel (lemon)-shaped with bipolar mucoid plugs. Ascaris eggs are mammillated, Enterobius eggs are flattened on one side, and hookworm eggs are thin-shelled with a segmented embryo.
Which public health measure best interrupts transmission of Trichuris trichiura?
Whipworm eggs embryonate in soil contaminated by human faeces and are then swallowed, so sanitation breaks the cycle. Mosquito, pork and snail control target other parasites.
An itchy papulovesicular rash on the feet of a barefoot farmer ('ground itch') is caused by skin penetration of:
Ground itch is the local reaction to hookworm L3 larvae entering the skin. Avian schistosome cercariae cause swimmer's itch after water exposure, not soil contact.
Which of these parasites is a roundworm rather than a fluke?
Ascaris is a nematode. Fasciolopsis and both Schistosoma species are trematodes (flukes).
Enterobius vermicularis is transmitted when a person swallows which stage?
Pinworm eggs become infective within hours on perianal skin and are swallowed via fingers, fomites or dust. Enterobius has no cyst or larval skin-penetrating stage.
Adult females reaching 20–35 cm make which worm the largest nematode found in the human intestine?
Ascaris lumbricoides is the largest intestinal roundworm. Hookworms and pinworms are about 1 cm, and whipworms about 3–5 cm.
Which statement about Ascaris lumbricoides is FALSE?
Ascaris has a direct life cycle with no intermediate host; eggs mature in soil. Larval lung migration and its large size are true features.
A night-time blood sample from a patient with lymphoedema is examined for Wuchereria bancrofti. Which stage is sought?
Adult W. bancrofti live in lymphatics and release sheathed microfilariae that circulate with nocturnal periodicity. Filariae produce no eggs, trophozoites or oocysts in blood.
Which statement about hookworm infection is FALSE?
Hookworms are nematodes and are diagnosed by thin-shelled eggs in stool; trophozoites are protozoan stages. The other statements are correct.
In nematode life cycles, the filariform (third-stage) larva is best described as the:
Filariform L3 larvae (e.g. hookworm, Strongyloides) are non-feeding infective larvae that penetrate skin. Rhabditiform larvae are the feeding, non-infective form.
Which infection does not typically cause splenomegaly?
Ascaris lives in the intestinal lumen and does not enlarge the spleen. Kala-azar and malaria cause marked splenomegaly, and S. mansoni causes it through portal hypertension.
Enterobiasis is the medical term for infection with which worm?
Enterobius vermicularis, the pinworm, causes enterobiasis. Hookworm infection is ancylostomiasis, roundworm is ascariasis and whipworm is trichuriasis.
Infection with the large intestinal roundworm Ascaris lumbricoides is called:
Ascariasis is caused by A. lumbricoides. The other names refer to hookworm, pinworm and whipworm infections.
The lymphedema of elephantiasis in lymphatic filariasis is due mainly to:
Adult worms and inflammatory reactions damage and block lymphatics, causing lymph stasis, fibrosis and swelling. Circulating microfilariae alone cause little disease.
Ancylostomiasis refers to infection with:
Ancylostoma duodenale (with Necator americanus) is a hookworm; the disease is ancylostomiasis. Ascariasis, enterobiasis and trichuriasis are the other worms.
Adult Wuchereria bancrofti worms reside in the:
Adults live in lymphatics and release microfilariae into the blood. Subcutaneous tissue and eye are sites for Onchocerca and Loa loa.