Tolerance to diethylcarbamazine-medicated salt in individuals infected with Onchocerca volvulus.

The tolerance of Onchocerca volvulus-infected individuals to diethylcarbamazine (DEC)-medicated salt (0.33% w/w) was assessed in 1996 in Tanzania in a double-blind placebo-controlled hospital-based trial involving 4 groups, each of 10 adult males. Groups I and II had O. volvulus microfilariae (mf) only, group III had both O. volvulus and Wuchereria bancrofti mf, and group IV had W. bancrofti mf only. Groups I, III and IV received DEC-medicated salt, whereas group II was a control to group I and received normal cooking salt. Medication was given for 10 days. The most pronounced adverse reactions in groups I and III were mild-to-moderate itching and rash, beginning after 3-4 days and lasting for the remaining medication period. The reactions did not interfere with normal daily activities. By 20 days after the end of medication, adverse reactions had disappeared in all individuals. The low daily dose of DEC had no significant effect on the O. volvulus pre-medication mf geometric mean intensities (GMIs). In contrast, the medication significantly reduced the pre-medication W. bancrofti mf GMIs. The prospects for using DEC-medicated salt for control of bancroftian filariasis in areas where incidental infections with O. volvulus occur are discussed.