Microfilariae exhibit a marked periodicity depending on the species involved, therefore the time of specimen collection is critical Please note where the patient has travelled. Loa loa — (10 AM to 2 PM) Brugia or Wuchereria — Pacific region Noon to 8pm, Rest of World 8pm-4am Mansonella and Onchocerca — any time
The filarial worms are arthropod transmitted parasites of the lymphatic, subcutaneous, and cutaneous tissues of humans. All share a unique charact¬eristic: the adult female worm produces a primitive larva called a microfilaria, which is found in the peripheral blood or in the skin and cutaneous tissues. Certain species of microfilariae circulate in the blood with a well defined circadian rhythm or "periodicity" which may be nocturnal or diurnal; other species lack periodicity and circulate in the blood at all hours of the day and night. It is important to find out where the patient has travelled to determine the most likely periodicity.