The use of continuous low-dosage copper sulfate as a molluscicide on an irrigation scheme in Kenya.

On a developing irrigation scheme in Kenya where there was a potential danger of Schistosoma mansoni transmission, copper sulfate at a concentration of between 0.125 p.p.m. and 0.25 p.p.m. was introduced as soon as water started flowing into the canals; there was no pre-sulfation at a higher concentration and mechanical barriers were not used.It was hoped that if this method proved successful it could be adopted for the routine control of bilharziasis, but as it proved impossible to provide day-to-day supervision, no definite conclusions as to the efficacy of the method can be made. The available data, however, indicated that at an average of 0.25 p.p.m. a barrier was created which was lethal to snails which passed through it, but that at an average of 0.125 p.p.m. results were indeterminate.Further trials to obtain more precise data on the mechanism of chemical barriers are recommended.