Virology: rabies diagnosis: 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 · Virology: rabies diagnosis

Sample item

A man with a dog bite 6 weeks ago has hydrophobia, aerophobia and agitation. Which ante-mortem specimen has the highest diagnostic yield?

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

The answer and the reasoning

B. Skin biopsy from the nape of the neck for rabies antigen or RNA

Rabies virus spreads centrifugally from the brain along nerves, reaching hair follicles. A nuchal skin biopsy shows viral antigen in cutaneous nerves by direct fluorescent antibody, and RNA by RT-PCR, and saliva RT-PCR can be added. Serum antibody usually appears late in unvaccinated patients, and the virus does not grow on blood agar.

Option by option

  • A. Serum rabies antibody in the first week of illness

    Serum antibodies are usually absent in the first week of illness.

  • B. Skin biopsy from the nape of the neck for rabies antigen or RNA (correct)

    Correct. Nuchal skin biopsy detects antigen around hair follicle nerves.

  • C. Stool PCR

    Rabies is not a gut infection and stool testing has no value.

  • D. Blood culture on blood agar

    Rabies virus is not a bacterium and cannot be cultured on blood agar.

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 B, Skin biopsy from the nape of the neck for rabies antigen or RNA. Rabies virus spreads centrifugally from the brain along nerves, reaching hair follicles.

Why is "Serum rabies antibody in the first week of illness" not the answer?

Serum antibodies are usually absent in the first week of illness.

Why is "Stool PCR" not the answer?

Rabies is not a gut infection and stool testing has no value.

Why is "Blood culture on blood agar" not the answer?

Rabies virus is not a bacterium and cannot be cultured on blood agar.

What concept does this question test?

It tests Virology: rabies diagnosis in Microbiology. A nuchal skin biopsy shows viral antigen in cutaneous nerves by direct fluorescent antibody, and RNA by RT-PCR, and saliva RT-PCR can be added. Serum antibody usually appears late in unvaccinated patients, and the virus does not grow on blood agar.

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 Virology: rabies diagnosis?

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.