The improvement of maintenance conditions for wild-caught Chrysops silacea and the production of infective larvae of Loa loa.

Previous reports have shown that Chyrsops silacea survive poorly in captivity. Only 5% survive for more than 12 days, which is the time required for Loa loa microfilariae to develop into infective larvae. Improved maintenance conditions for C. silacea for the production of infective larvae were studied. Wild-caught female C. silacea were allowed to feed to repletion on mandrills, (Mandrillus sphinx), which were microfilaremic with human L. loa or on uninfected laboratory rats. Under optimal conditions 30-50% of flies engorged. The survival rates of fed and unfed flies were compared under a variety of conditions. Survival rates varied considerably under the various maintenance conditions. Ingestion of either rat or mandrill blood made no significant difference to fly survival. Optimal conditions were found to be as follows: one to two flies per sterilized jar with damp sand, constant access to sterilized 10% sucrose, a temperature of 23-29 degrees C and 84-98% relative humidity. Under these conditions 42% of the flies survived until day 12, when maximal numbers of infective larvae were present in the head.