A 30-year-old woman from Kerala presents with lymphoedema of the right leg, episodic adenolymphangitis and chyluria. Microfilaria are found in a midnight blood sample. Which feature on microscopy would BEST differentiate Wuchereria bancrofti from Brugia malayi microfilariae?

• A Presence of a sheath in W. bancrofti but not B. malayi
• B B. bancrofti has a longer length (>300 µm) compared to B. malayi
• C B. malayi shows nocturnal subperiodicity in India, while W. bancrofti is always aperiodic
• D Absence of nuclei in the tail tip in W. bancrofti; B. malayi has two discrete nuclei in the tail tip ✓

Explanation

Both Wuchereria bancrofti and Brugia malayi microfilariae are sheathed and show nocturnal periodicity in most regions. The definitive distinguishing feature is in the tail: W. bancrofti has no nuclei in the tail tip, while B. malayi has two distinct, separate nuclei at the tail tip — this is a classic NEET PG discriminator. B. malayi microfilariae are also slightly smaller. In India, B. malayi in coastal Kerala shows nocturnal subperiodicity (not diurnal aperiodicity).

Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.