Trials of ecological and chemical measures for the control of Schistosoma haematobium transmission in a Volta Lake village.

Urinary schistosomiasis is highly prevalent along the shores of the Volta Lake in Ghana, where transmission occurs focally in man-water contact sites. The intermediate host, Bulinus truncatus rohlfsi, prefers to harbour in Ceratophyllum, a common aquatic weed in the lake. Removal of this weed reduced the density of both infected and uninfected snails, but not sufficiently to interrupt transmission.Niclosamide was applied at 1, 0.7, and 0.5 mg/l in combination with weed removal at five water contact sites in December, January, and February, respectively. Plastic sheets were used to isolate treated sites from the main body of the lake. Snail surveys were carried out at short intervals to assess the effectiveness of these intervention measures. Niclosamide at 0.5 mg/l applied after weed removal was effective in killing the snails. The overall results indicate that snail control along the entire lake shore is impossible but that focal control of cercarial transmission at water contact sites is attainable and shows promise.