Where is Wuchereria present during daytime, when microfilaria are not seen in blood capillaries?

INI-CET EXAM -2025

Microbiology

Easy

Appeared in: INI-CET EXAM -2025

Explanation

The parasite Wuchereria bancrofti exhibits a characteristic behavior known as nocturnal periodicity.
This means its larvae, called microfilariae, are mostly absent from the peripheral (surface) blood vessels during the day.
During daytime hours, the microfilariae sequester or accumulate in the capillaries and small blood vessels of deep internal organs.
The primary site for this daytime sequestration is the lungs.
The microfilariae then migrate into the peripheral bloodstream at night, typically peaking between 10 PM and 2 AM.

Option A: While the spleen is a deep visceral organ with a rich blood supply, it is not the primary site where Wuchereria microfilariae sequester during the day. The main reservoir is the pulmonary vasculature.
Option B: Similar to the spleen, the liver's extensive capillary network might harbor some microfilariae, but it is not considered the principal site of daytime sequestration. The lungs are the main location.
Option D: The kidneys are deep organs, and obstruction of retroperitoneal lymphatics in bancroftian filariasis can lead to chyluria (lymph in the urine), but the kidney's blood vessels are not the primary site for the daytime sequestration of microfilariae.

Visual 1: Diagram - Illustrating the concept of nocturnal periodicity. The diagram can show a 24-hour clock with two human figures. The daytime figure shows microfilariae concentrated in the lungs, while the nighttime figure shows them dispersed in the peripheral blood vessels.
Visual 2: Micrograph - A stained blood smear showing the characteristic appearance of a Wuchereria bancrofti microfilaria, highlighting its sheath.

Clinical Relevance

Nursing practice connection: Knowing The concept tested is the nocturnal periodicity of Wuchereria bancrofti microfilariae and their location during the daytime helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
Understanding nocturnal periodicity is crucial for the diagnosis of lymphatic filariasis. Blood samples for microscopic examination must be collected at the correct time, typically at night between 10 PM and 2 AM, to ensure the highest chance of detecting the circulating microfilariae.
A daytime blood sample is likely to produce a false-negative result for microfilaremia in a patient with a nocturnally periodic strain.
What if? If the infection were caused by Loa loa (the African eye worm), the opposite would be true. Loa loa exhibits diurnal periodicity, so blood samples should be collected during the day (around noon) to detect its microfilariae.

How to Approach the Question

First, identify the key organism in the question: Wuchereria.
Recall the major characteristic associated with this parasite's life cycle, specifically the behavior of its larval stage (microfilaria).
The question asks for the location during the 'daytime' when it's 'not seen in blood capillaries'. This is a direct clue to the concept of 'periodicity'.
Wuchereria bancrofti is known for 'nocturnal periodicity', meaning the larvae are in the peripheral blood at night and retreat to deep organs during the day.
Evaluate the options provided, which are all deep organs. The primary and most well-known site for this daytime sequestration is the lungs.
Therefore, select 'Lungs' as the correct answer.

Concept Tested & Keywords

Concept Tested: The concept tested is the nocturnal periodicity of Wuchereria bancrofti microfilariae and their location during the daytime.
Stem keywords: Wuchereria, daytime, microfilaria, blood capillaries
Lead-in keywords: Where is

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