ABSENCE OF SPERM FROM THE SEMINAL RECEPTACLE OF FEMALE ONCHOCERCA-VOLVULUS FOLLOWING MULTIPLE DOSES OF INVERMECTIN

It is already known that multiple doses of ivermectin have a profound effect on embryonic development in Onchocerca volvulus and that this a ppears to operate mainly at the single cell stage. To investigate this further, we examined adult female 0. volvulus originating from patien ts treated either with placebo or one, four or five doses of ivermecti n. The reproductive organs were dissected out of the worm and examined for evidence of oogenesis and for the quantity of sperm and oocytes i n the seminal receptacles. A single dose of ivermectin had no measurab le effect on oogenesis or on the amount of sperm and oocytes compared to placebo. However after multiple doses of ivermectin a significantly lower proportion of seminal receptacles contained sperm and there was a significantly higher proportion of ovaries with impaired oogenesis compared to placebo. It is concluded that the reduction in the number of multicellular embryonic stages from worms exposed to multiple doses of ivermectin is due, at least in part, to a major reduction in the e ffective insemination of female worms and to a minor impairment of oog enesis.