ULTRASONOGRAPHIC ASSESSMENT OF THE ADULTICIDAL EFFICACY OF REPEAT HIGH-DOSE IVERMECTIN IN BANCROFTIAN FILARIASIS

Since diethylcarbamazine, the drug recommended for treatment of lympha tic filariasis, seems only partially effective against the adult worm, intense interest persists in identifying a macrofilaricidal drug for this infection. To evaluate directly in vivo the macrofilaricidal acti vity of repeat high-dose ivermectin, 15 men who had living adult Wuche reria bancrofti detected in the scrotal area by ultrasound were treate d with 400 mu g/kg of ivermectin at 2-week intervals for 6 months (tot al dose, 4.8 mg/kg). Serial ultrasound examinations were performed bef ore, during, and for 6 months after treatment. Profound suppression of microfilaraemia followed the first dose of ivermectin, but movements characteristic of the adult worm on ultrasound remained unchanged both in location and pattern. Even when given in total doses of 4.8 mg/kg, ivermectin appears to have no observable activity against adult W. ba ncrofti, although its ability to suppress microfilaraemia makes it pot entially useful for the control of lymphatic filariasis.