Parasitology: Hymenolepis nana: 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: Hymenolepis nana

Sample item

A 6-year-old child in a crowded hostel has recurrent abdominal pain and diarrhoea. Stool shows small round eggs with polar filaments and a hexacanth embryo, and the burden of worms is heavy despite no new exposure. Which feature of the life cycle explains the heavy burden?

AIngestion of encysted larvae in raw fishBInternal autoinfection, because eggs hatch within the same host's intestineCLarval migration through the lungs before maturationDAn obligatory beetle intermediate host in every cycle

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

The answer and the reasoning

B. Internal autoinfection, because eggs hatch within the same host's intestine

Hymenolepis nana, the dwarf tapeworm, can complete its life cycle in a single host because eggs hatch in the small intestine and the larvae develop into adults without leaving the body. Transmission is faecal-oral, and an arthropod host such as a flour beetle is optional. Praziquantel is the drug of choice.

Option by option

A. Ingestion of encysted larvae in raw fish
Raw fish is the source of Diphyllobothrium latum.
B. Internal autoinfection, because eggs hatch within the same host's intestine (correct)
Eggs hatching inside the intestine allow worm numbers to rise without new exposure.
C. Larval migration through the lungs before maturation
Pulmonary migration is a feature of Ascaris and hookworm.
D. An obligatory beetle intermediate host in every cycle
A beetle host is optional and not obligatory for this species.

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.

Questions about this Microbiology question

What is the answer to this Microbiology question?

The best answer is B, Internal autoinfection, because eggs hatch within the same host's intestine. Hymenolepis nana, the dwarf tapeworm, can complete its life cycle in a single host because eggs hatch in the small intestine and the larvae develop into adults without leaving the body.

Why is "Ingestion of encysted larvae in raw fish" not the answer?

Raw fish is the source of Diphyllobothrium latum.

Why is "Larval migration through the lungs before maturation" not the answer?

Pulmonary migration is a feature of Ascaris and hookworm.

Why is "An obligatory beetle intermediate host in every cycle" not the answer?

A beetle host is optional and not obligatory for this species.

What concept does this question test?

It tests Parasitology: Hymenolepis nana in Microbiology. Transmission is faecal-oral, and an arthropod host such as a flour beetle is optional. Praziquantel is the drug of choice.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. 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: Hymenolepis nana?

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.