Parasitology: Ascaris lumbricoides: 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: Ascaris lumbricoides

Sample item

A 5-year-old rural child has cough, wheeze and transient pulmonary infiltrates with 12% eosinophils. Stool microscopy shows no eggs. What is the most likely explanation?

AAscaris never sheds eggs in stoolBLarvae are migrating through the lungs, and adult worms have not yet begun laying eggsCEggs are shed only at night, so the sample missed themDAdult worms inhabit the bronchi and release eggs in sputum

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

The answer and the reasoning

B. Larvae are migrating through the lungs, and adult worms have not yet begun laying eggs

In Loeffler syndrome, ingested Ascaris eggs hatch, larvae penetrate the gut, travel to the lungs through the blood, ascend the airway and are swallowed. This takes 1 to 2 weeks and eosinophilic pneumonitis results. Adult worms mature in the small intestine and eggs appear in stool only after about 2 months.

Option by option

A. Ascaris never sheds eggs in stool
Fertilised eggs are shed daily in stool once females mature, and stool microscopy diagnoses established infection.
B. Larvae are migrating through the lungs, and adult worms have not yet begun laying eggs (correct)
Correct. The lung phase precedes egg production by roughly 2 months.
C. Eggs are shed only at night, so the sample missed them
Nocturnal shedding applies to pinworm perianal egg laying and microfilariae in blood, not Ascaris.
D. Adult worms inhabit the bronchi and release eggs in sputum
Adults live in the small intestine, and only larvae pass through the lung.

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, Larvae are migrating through the lungs, and adult worms have not yet begun laying eggs. In Loeffler syndrome, ingested Ascaris eggs hatch, larvae penetrate the gut, travel to the lungs through the blood, ascend the airway and are swallowed.

Why is "Ascaris never sheds eggs in stool" not the answer?

Fertilised eggs are shed daily in stool once females mature, and stool microscopy diagnoses established infection.

Why is "Eggs are shed only at night, so the sample missed them" not the answer?

Nocturnal shedding applies to pinworm perianal egg laying and microfilariae in blood, not Ascaris.

Why is "Adult worms inhabit the bronchi and release eggs in sputum" not the answer?

Adults live in the small intestine, and only larvae pass through the lung.

What concept does this question test?

It tests Parasitology: Ascaris lumbricoides in Microbiology. This takes 1 to 2 weeks and eosinophilic pneumonitis results. Adult worms mature in the small intestine and eggs appear in stool only after about 2 months.

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: Ascaris lumbricoides?

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.