Parasitology: Schistosoma mansoni acute infection: practice question

A Microbiology question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Microbiology · Parasitology: Schistosoma mansoni acute infection

Sample item

A 24-year-old man returns from a trip to Africa with fever, urticaria, cough and hepatosplenomegaly 4 weeks after swimming in a freshwater lake. Eosinophilia is marked, but three stool samples show no eggs. Why is stool microscopy negative?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

B. The illness precedes the start of egg laying by adult worms

Acute schistosomiasis (Katayama fever) is a systemic hypersensitivity reaction occurring 2 to 8 weeks after infection while schistosomulae mature and before egg production starts. Eggs of S. mansoni are passed in stool once adult worms in the mesenteric venules begin laying. Serology and repeat stool testing later establish the diagnosis, and treatment is with praziquantel, often with steroids for severe disease.

Option by option

  • A. Adult worms live in the vesical plexus, so eggs never reach the gut

    Adult S. mansoni lives in mesenteric venules, whereas S. haematobium inhabits the vesical plexus.

  • B. The illness precedes the start of egg laying by adult worms (correct)

    Katayama fever occurs before the prepatent period ends, so no eggs are present.

  • C. S. mansoni eggs leave the host only in urine

    S. mansoni eggs are excreted in stool with their lateral spine, and urine passage is typical of S. haematobium.

  • D. Egg excretion begins only after hepatic fibrosis develops

    Egg excretion does not depend on fibrosis and starts weeks after exposure.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

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Questions about this Microbiology question

What is the answer to this Microbiology question?

The best answer is B, The illness precedes the start of egg laying by adult worms. Acute schistosomiasis (Katayama fever) is a systemic hypersensitivity reaction occurring 2 to 8 weeks after infection while schistosomulae mature and before egg production starts.

Why is "Adult worms live in the vesical plexus, so eggs never reach the gut" not the answer?

Adult S. mansoni lives in mesenteric venules, whereas S. haematobium inhabits the vesical plexus.

Why is "S. mansoni eggs leave the host only in urine" not the answer?

S. mansoni eggs are excreted in stool with their lateral spine, and urine passage is typical of S. haematobium.

Why is "Egg excretion begins only after hepatic fibrosis develops" not the answer?

Egg excretion does not depend on fibrosis and starts weeks after exposure.

What concept does this question test?

It tests Parasitology: Schistosoma mansoni acute infection in Microbiology. Eggs of S. mansoni are passed in stool once adult worms in the mesenteric venules begin laying. Serology and repeat stool testing later establish the diagnosis, and treatment is with praziquantel, often with steroids for severe disease.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Parasitology: Schistosoma mansoni acute infection?

Make a one-line identity card for each organism: shape and stain, defining test, toxin, disease and drug. Then use the flashcards and the other Microbiology questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.