Onchocerca raillieti: release from skin snips, maintenance in vitro and periodicity of microfilariae.

Several media were tested for the release of Onchocerca raillieti microfilariae from skin snips and for their subsequent in vitro maintenance. Tyrode's solution containing 20% equine serum and antibiotics was the best medium tested, followed by phosphate buffered saline. Tyrode's solution alone or distilled water were poor media. A temperature 7-12 degrees C lower than the host's body temperature favoured release of the microfilariae from skin snips. The microfilariae were best maintained at 4-10 degrees C, when they remained alive for up to 5 days. O. raillieti microfilariae had an evening periodicity which could be related to a possible vector's peak of feeding activity.