Single doses of ivermectin 400 micrograms/kg-1: the most effective dosage in bancroftian filariasis.

Forty-three Wuchereria bancrofti carriers were given four successive semi-annual single doses of ivermectin 100 micrograms.kg-1 (IVER 100). The geometric mean microfilaremia (mf) recurrence percentage as compared to the pre-initial treatment mf level was 35%, 21%, 17% and 17% at 6, 12, 18 and 24 months, respectively. However, the recurrence of mf 6 months after the fourth treatment remained high in several individuals: 15 have been considered as 'bad responders' and 28 as 'good responders' individuals. At month 24 (M 24), they were randomly allocated into 2 groups. A first group was treated with a fifty and a sixth dose of IVER 100, at M24 and M30, respectively; the second one was treated, at the same time, with single doses of IVER 400 micrograms.kg-1 (IVER 400). At M 36, the mf recurrence percentage (mf M36/mf M0) was significantly higher in patients treated with IVER 100 than IVER 400 (11% vs 1%, p < 10(-4). From the group IVER 100, 6 out of the 8 'bad responders' remained 'bad responders' whereas there were none of the 7 in the group IVER 400. Moreover, there were only 2 more patients in the group IVER 100 showing sustained complete zero mf, whereas they were 13 in the group IVER 400. Single doses of IVER 400 were effective on 'bad responders'; IVER 400 must be recommended for semi-annual mass treatment in bancroftian filariasis.

A single diethylcarbamazine dose for treatment of Wuchereria bancrofti carriers in French Polynesia: efficacy and side effects.

In the fall of 1988, 14 Tahitian Wuchereria bancrofti carriers were treated by a single diethylcarbamazine (DEC) 3 mg/kg dose. Determination of blood microfilarial (mf) density was carried out on days 0, 7, 14, 30, 90 and 180 using the membrane filtration technique. Clinical signs and side effects were noted during the 3 days following treatment. Complete clearance of microfilaremia was observed in two carriers (negativation rate 14%). A decrease of mf density was noted in all of the 14 carriers, ranging from 35.2 to 99.2% (median 78.75%). The percentage decrease in mf density, determined for the whole group from the geometric mean of the 14 mf counts, was 86% by day 7 and reached 95% by day 180. Side effects were observed in 10 patients (71%) of whom 3 only were unable to perform usual activities for less than 24 hours. Though it induced an incomplete initial mf clearance, a single DEC 3 mg/kg dose was effective in reducing about 90% of the microfilaremia and in sustaining this reduction over a period of six months. Such long-term reduction (comparable to that observed in W. bancrofti carriers treated with a daily DEC 6 mg/kg dose during 12 days) is likely responsible for the consistent decrease of total mf counts observed in the Tahitian population which has been treated for years with single DEC doses given every six months.