Moulting and exsheathment of the infective larvae of Onchocerca lienalis (Filarioidea) in vitro.

Fourth-stage larvae (L4) of the cattle filarial parasite Onchocerca lienalis were produced from third stage forms (L3) and maintained in vitro using a variety of culture media and feeder cell layers. Up to 50% of the L3 larvae moulted to the fourth stage in the presence of two jird (Meriones unguiculatus) cell lines, a monkey kidney cell line and also with Vero cells. Moulting took place 2-5 days after of the initiation of the cultures: These L4 parasites could be maintained in a healthy condition for up to 88 days, although no significant increases in size of these larvae were observed during the culture period. The medium giving the most promising results, both in terms of moulting and survival, was 199 supplemented with heat inactivated foetal bovine serum (20%) and glucose (2 mg/ml). The feeder layer cells could be replaced by fresh jird red blood cells. Moulting of parasites occurred in medium alone but the viability was reduced under these conditions.