Microfilariae

Function

The Microfilariae test is a microscopic examination of blood to identify the presence of larval stages (microfilariae) of filarial parasites. These parasites are nematodes (roundworms) that inhabit the lymphatic system or subcutaneous tissues of humans, transmitted via the bites of infected mosquitoes or flies.

Why it is Ordered

This test is ordered for patients presenting with symptoms of Lymphatic Filariasis (Elephantiasis), such as severe limb swelling, scrotal swelling (hydrocele), or tropical pulmonary eosinophilia. It is particularly relevant for individuals living in or traveling from endemic regions in Asia, Africa, and South America.

Associated Conditions

• Wuchereria bancrofti: Responsible for the majority of lymphatic filariasis cases.
• Brugia malayi/timori: Other causes of lymphatic swelling.
• Loa loa: Known as the 'African eye worm,' where microfilariae are found in the blood but adults migrate under the skin/eye.

Diagnostic Techniques

Detection often requires specialized techniques like the Knott’s concentration method or membrane filtration to increase sensitivity. Because microfilariae often exhibit 'nocturnal periodicity,' blood must be drawn between 10:00 PM and 2:00 AM for certain species (like W. bancrofti) when the larvae migrate from internal organs into the peripheral bloodstream.