Persistence of microfilaremia in bancroftian filariasis after diethylcarbamazine citrate therapy.

Of 58 patients in Leogane, Haiti, infected with Wuchereria bancrofti and treated with diethylcarbamazine citrate (DEC-C) at 6 mg/kg per day for 12 days (= 72 mg/kg), 38 (66%) of 58 continued to harbor low numbers of circulating microfilariae (median microfilariae could be demonstrated in 7 (37%) of 19 patients, with a median microfilarial density of 8 mf/ml. Three patients who continued to have circulating microfilariae after two courses of DEC-C were treated a third time. Two (67%) of the three remained microfilaria positive, both with 1 mf/ml. The results of this study clearly indicate that a high percentage of persons infected with W. bancrofti and treated with one or multiple courses of DEC-C may continue to have circulating microfilariae after treatment. We suspect that these low-level reservoir carriers substantially contribute to the transmission of filariasis and may well account for the resurgence of infection levels following control efforts.