A series of compounds that apparently disrupt hormonally regulated processes in insects have been examined for effects on the viability and microfilarial production of adult Brugia pahangi cultured in vitro. The azasteroids, 25-azacoprostane and 25-azacholestane, inhibited the production of microfilariae at 5 ppm, the former also exhibiting macrofilaricidal activity at this concentration. The brassinosteroids examined inhibited microfilarial production at 5 ppm but did not affect worm viability. Azadirachtin also proved to be a significant inhibitor of microfilarial release without effect on worm motility or viability. Of all the compounds tested, the non-steroidal amines appeared to be the most promising as potential filaricides, several of them proving to be macrofilaricidal at 1 ppm and affecting microfilarial production at even lower concentrations.
