Advantages of ivermectin at a single dose of 400 μg/kg compared with 100 μg/kg for community treatment of lymphatic filariasis in Polynesia

Abstract

In April and October in 1991–1993, 5 supervised single doses of ivermectin were given to inhabitants aged ⩾3 years in a Polynesian district: the first 3 treatments were with 100 μg/kg and the 2 latter with 400 μg/kg. At each treatment, about 97% of the eligible population (899) were treated and blood samples were collected just before treatment from 96% of the 613 inhabitants aged ⩾15 years. Following the 5 successive treatments, adverse reactions were observed in, respectively, 23·8, 13, 6·2, 13·6 and 7·9% of the microfilariae (mf) carriers, and in less than 1% of amicrofilaraemic subjects. Neither the frequency nor the intensity of adverse reactions was significantly different between single doses of 100 μg/kg and 400 μg/kg. Although the geometric mean microfilaraemia (GMM) was reduced, the mf carrier prevalence remained unchanged before and after 3 mass treatments with 100 μg/kg (21·4 and 20·7% respectively), and the mf recurrence rate 6 months after each dose of 100 μg/kg was roughly stable (respectively, 34·3%, 21·6% and 31·2% of the initial GMM). In contrast, after one dose round of 400 μg/kg, the mf carrier prevalence decreased significantly to 14·9% ( P < 10 −6 ), and the mf recurrence rate dropped to 9·9% ( P < 10 −3 ) of the initial GMM. These results confirm the safety and the effectiveness of 400 μg/kg of ivermectin for lymphatic filariasis control.