Parasitology: Loa loa: 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: Loa loa

Sample item

A man from Cameroon has transient painless subcutaneous swellings on the forearm and once saw a worm cross his conjunctiva. Blood films show 45,000 microfilariae/mL. Mass ivermectin treatment for onchocerciasis is planned in his village. What is the specific concern for him?

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

The answer and the reasoning

D. Severe encephalopathy from rapid killing of a very heavy Loa loa microfilarial load

Loa loa, spread by Chrysops flies, causes Calabar swellings and eye worm. In patients with more than about 30,000 microfilariae/mL, ivermectin can cause serious adverse events including encephalopathy and coma, so such patients are excluded from mass treatment in co-endemic areas. Management involves albendazole and careful treatment strategies.

Option by option

  • A. Development of resistance in adult worms to ivermectin

    Resistance is a population concern and not an individual hazard at the time of treatment.

  • B. Mazzotti reaction with permanent ocular damage

    The Mazzotti reaction is a reaction to microfilarial death in onchocerciasis, most associated with diethylcarbamazine.

  • C. Severe haemolysis from G6PD deficiency

    Ivermectin is not associated with haemolysis in G6PD deficiency, unlike primaquine.

  • D. Severe encephalopathy from rapid killing of a very heavy Loa loa microfilarial load (correct)

    Heavy microfilaraemia puts him at risk of fatal reactions after ivermectin.

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 D, Severe encephalopathy from rapid killing of a very heavy Loa loa microfilarial load. Loa loa, spread by Chrysops flies, causes Calabar swellings and eye worm.

Why is "Development of resistance in adult worms to ivermectin" not the answer?

Resistance is a population concern and not an individual hazard at the time of treatment.

Why is "Mazzotti reaction with permanent ocular damage" not the answer?

The Mazzotti reaction is a reaction to microfilarial death in onchocerciasis, most associated with diethylcarbamazine.

Why is "Severe haemolysis from G6PD deficiency" not the answer?

Ivermectin is not associated with haemolysis in G6PD deficiency, unlike primaquine.

What concept does this question test?

It tests Parasitology: Loa loa in Microbiology. In patients with more than about 30,000 microfilariae/mL, ivermectin can cause serious adverse events including encephalopathy and coma, so such patients are excluded from mass treatment in co-endemic areas. Management involves albendazole and careful treatment strategies.

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: Loa loa?

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.