Clearance of circulating filarial antigen as a measure of the macrofilaricidal activity of diethylcarbamazine in Wuchereria bancrofti infection.

Small doses of diethylcarbamazine (DEC) clear microfilariae (MF) from the blood of Wuchereria bancrofti-infected persons, but the dose and regimen required to kill adult worms is not clearly defined. A prospective study was undertaken to examine the macrofilaricidal effect of DEC and the ability of an assay for circulating filarial antigen (CFA) to define the effect. Twenty-five MF-positive subjects and 7 MF-negative but CFA-positive subjects were treated with DEC and followed for 18 months. Of the 25 MF-positive patients, 24 cleared MF, and 22 of 26 CFA-positive subjects cleared CFA. A significantly greater decrease in antifilarial IgG4 was seen in patients who cleared CFA than in those who did not. The complete clearance of CFA observed after therapy with DEC indicates that assessment of CFA clearance is a useful means for detecting macrofilaricidal effects of antifilarial chemotherapy.