Parasitology: Onchocerca volvulus: 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: Onchocerca volvulus

Sample item

A farmer from West Africa living near a fast-flowing river has itchy dermatitis, subcutaneous nodules and visual loss. A skin snip shows microfilariae. Which drug is the treatment of choice, and why is another filaricide avoided?

ADiethylcarbamazine, because ivermectin worsens ocular diseaseBAlbendazole alone, because it is microfilaricidal in skinCPraziquantel, because it kills adult filarial wormsDIvermectin, because diethylcarbamazine can provoke severe reactions and ocular damage

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

The answer and the reasoning

D. Ivermectin, because diethylcarbamazine can provoke severe reactions and ocular damage

Onchocerciasis (river blindness) is transmitted by Simulium blackflies. Ivermectin kills microfilariae and is given annually in mass programmes. Diethylcarbamazine is avoided because the rapid death of microfilariae triggers the Mazzotti reaction and can harm the eyes, and doxycycline targets Wolbachia to sterilise adult worms.

Option by option

A. Diethylcarbamazine, because ivermectin worsens ocular disease
DEC is avoided in onchocerciasis, and ivermectin does not worsen eye disease.
B. Albendazole alone, because it is microfilaricidal in skin
Albendazole alone has limited microfilaricidal effect in onchocerciasis.
C. Praziquantel, because it kills adult filarial worms
Praziquantel acts on cestodes and trematodes, not filariae.
D. Ivermectin, because diethylcarbamazine can provoke severe reactions and ocular damage (correct)
Correct. Ivermectin is preferred, and DEC risks the Mazzotti reaction.

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 D, Ivermectin, because diethylcarbamazine can provoke severe reactions and ocular damage. Onchocerciasis (river blindness) is transmitted by Simulium blackflies.

Why is "Diethylcarbamazine, because ivermectin worsens ocular disease" not the answer?

DEC is avoided in onchocerciasis, and ivermectin does not worsen eye disease.

Why is "Albendazole alone, because it is microfilaricidal in skin" not the answer?

Albendazole alone has limited microfilaricidal effect in onchocerciasis.

Why is "Praziquantel, because it kills adult filarial worms" not the answer?

Praziquantel acts on cestodes and trematodes, not filariae.

What concept does this question test?

It tests Parasitology: Onchocerca volvulus in Microbiology. Ivermectin kills microfilariae and is given annually in mass programmes. Diethylcarbamazine is avoided because the rapid death of microfilariae triggers the Mazzotti reaction and can harm the eyes, and doxycycline targets Wolbachia to sterilise adult worms.

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: Onchocerca volvulus?

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.