IVERMECTIN OR DIETHYLCARBAMAZINE IN REPEATED SINGLE-DOSE TREATMENT OF BANCROFTIAN FILARIASIS - WHICH STRATEGY

58 apparently healthy Polynesian Wuchereria bancrofti carriers were randomly allocated to 5 treatment groups: 1) two annual doses of ivermectin 100 mcg/kg, 2) three semi-annual doses of ivermectin 100 mcg/kg, 3) two annual doses of diethylcarbamazine (DEC) 3 mg/kg, 4) three semi-annual doses of DEC 3 mg/kg, 5) two annual doses of DEC 6 mg/kg. Results observed during the 12-month period which followed last treatment have confirmed that efficacy of ivermectin is higher than that of DEC in terms of immediate clearance or complete negativation of microfilaremia, but not in terms of sustained reduction and that efficacy of repeated single doses of either DEC 3 mg/kg or ivermectin 100 mcg/kg is much higher when given semi-annually than annually. They also have indicated that (i) 6 months after last treatment: 3 semi-annual doses of 100 mca/ka of ivermectin have resulted in high reduction of microfilaremia (85 %) and, 2 annual doses of 6 mg/kg and 3 semi-annual doses of 3 mg/kg of DEC have resulted in even greater reduction (96 and 98 % respectively) and (ii): 12 months after last treatment, the greatest reductions of microfilaremia (95 and 92 %) have been observed in carriers treated, respectively, with 3 semi-annual doses of 3 mg/kg or with 2 annual doses of 6 mg/kg of DEC. These findings, and those of the preceeding 12-month study-period, indicate clearly that the repeated semi-annual administration of single doses of DEC (3 or 6 mg/kg) by reducing (or clearing) microfilaremia and thus resulting in dramatic decrease or suppression of the transmission by the mosquito vector, represents an effective strategy for lymphatic filariasis control programmes. In areas where populations are reluctant to repeated intake of DEC, the semi-annual administration of single doses of 100 mcg/kg of ivermectin might be considered as an alternative strategy.