Effect of two single doses of ivermectin in treatment of asymptomatic bancroftian filariasis in two villages in the Nile Delta, Egypt.

To evaluate the efficacy and longitudinal effect of two single (100 micrograms/kg) doses of ivermectin, 3 months apart, 240 asymptomatic male subjects from 2 endemic Egyptian villages were enrolled in a one-year double-blind study. Subjects aged 15-55 years were randomly assigned placebo (40) or ivermectin (200). Microfilaria (MF) density in 1 ml blood was measured by membrane filtration before and every 3 months after treatment. Initial mean MF density was 462 (range 14-2869/ml). Clinical examination performed daily for 3 days after each treatment revealed brief, mild side effects: fever, headache, weakness, nausea, and epigastric pain, with no adverse physical or laboratory findings. Three months after initial dose, 31% of MF counts had completely cleared; in the remainder, mean MF density was 11.0 (2.4% of pretreatment level). At 3, 6 and 9 months after the second dose there was complete MF clearance in 60%, 45% and 47%; in those still infected, MF densities were 1.7, 4.6 and 6.1% of the pretreatment level. Therefore, treatment with two doses of ivermectin reduced microfilaremia, without inducing severe side effects. Prolonged suppression of microfilaremia may indicate an effect of ivermectin on the adult worms and may reduce the potential for MF acquisition by mosquitoes, reducing transmission of lymphatic filariasis. It was concluded that ivermectin is a useful drug for public health measure, including asymptomatic filariasis patients.