Parasitology: Diphyllobothrium latum: 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: Diphyllobothrium latum

Sample item

A man who regularly eats raw freshwater fish has macrocytic anaemia and paraesthesiae. Operculated eggs are seen in his stool. Which mechanism explains his anaemia?

AThe tapeworm competes for dietary vitamin B12 in the small intestineBHaemolysis from parasite invasion of red cellsCChronic blood loss from mucosal attachmentDAutoimmune destruction of gastric parietal cells

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

The answer and the reasoning

A. The tapeworm competes for dietary vitamin B12 in the small intestine

Diphyllobothrium latum, the fish tapeworm, can absorb large amounts of vitamin B12 in the jejunum, causing megaloblastic anaemia with neurological features. Praziquantel or niclosamide treats the infection, and B12 is replaced. The second intermediate host is freshwater fish.

Option by option

A. The tapeworm competes for dietary vitamin B12 in the small intestine (correct)
Correct. Parasite uptake of B12 explains the megaloblastic anaemia.
B. Haemolysis from parasite invasion of red cells
Red cell invasion occurs in malaria and babesiosis.
C. Chronic blood loss from mucosal attachment
Blood loss is the mechanism for hookworm and gives microcytic anaemia.
D. Autoimmune destruction of gastric parietal cells
Parietal cell destruction causes pernicious anaemia without worm eggs.

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 A, The tapeworm competes for dietary vitamin B12 in the small intestine. Diphyllobothrium latum, the fish tapeworm, can absorb large amounts of vitamin B12 in the jejunum, causing megaloblastic anaemia with neurological features.

Why is "Haemolysis from parasite invasion of red cells" not the answer?

Red cell invasion occurs in malaria and babesiosis.

Why is "Chronic blood loss from mucosal attachment" not the answer?

Blood loss is the mechanism for hookworm and gives microcytic anaemia.

Why is "Autoimmune destruction of gastric parietal cells" not the answer?

Parietal cell destruction causes pernicious anaemia without worm eggs.

What concept does this question test?

It tests Parasitology: Diphyllobothrium latum in Microbiology. Praziquantel or niclosamide treats the infection, and B12 is replaced. The second intermediate host is freshwater fish.

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: Diphyllobothrium latum?

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.