Abstract

Diethylcarbamazine/albendazole (DEC/ALB) therapy is widely used in mass drug administration (MDA) programmes aimed at eliminating lymphatic filariasis. We studied the effects of repeated annual treatments with DEC/ALB on Wuchereria bancrofti microfilaraemia, filarial antigenaemia and IgG4 antibodies to Bm14 antigen. Fifty-seven subjects with asymptomatic microfilaraemia were treated with one or seven daily doses of DEC/ALB at time zero. All subjects were re-treated with single-dose DEC/ALB 12, 24 and 36 months later. The two treatment groups had comparable pre-treatment microfilaria counts. Multidose treatment cleared microfilaraemia more effectively than single-dose treatment. Filarial antigen levels decreased equally in both treatment groups. Total antigen clearance was observed in 29.6%, 52.0%, 63.6% and 79.5% of subjects at 12, 24, 36 and 48 months. These clearance rates are much higher than those observed in prior treatment trials with DEC or ivermectin. Antibody levels increased 4 weeks after treatment and then slowly decreased in most subjects. Antibody tests turned negative in 20%, 35%, 39.4% and 52.5% of treated subjects at 12, 24, 36 and 48 months post treatment. These results show that the studied parameters decline at different rates and to differing degrees following DEC/ALB treatment. These findings have important implications regarding strategies for monitoring the effects of MDA in populations.