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This image shows a microfilaria of Wucheria bancrofti, a parasitic nematode responsible for lymphatic filariasis. The microfilaria is characterized by its elongated, thread-like structure with a distinct, wavy appearance. It measures approximately 250-300 micrometers in length and 7-10 micrometers in width, with a coiled or serpentine shape visible in the smear. The sheath, a key diagnostic feature, is faintly stained and surrounds the larva, though it may not be prominently visible in all sections due to staining variability. The nucleus extends along the body, appearing as a series of dark-staining granules, though it does not reach the tail end, which is typically pointed and free of  nuclei.

The presence of W. bancrofti microfilariae in peripheral blood, especially at night (nocturnal periodicity), is indicative of an active infection, often associated with symptoms like lymphedema or elephantiasis if chronic.

Various mosquito species, including those from the Aedes, Anopheles, and Culex genera, can transmit the parasite. These mosquitoes often have peak biting activity during the night.