Further observations from St Lucia on control of Schistosoma mansoni transmission by provision of domestic water supplies.

Individual households in five settlements were provided with piped water in a pilot scheme to investigate the effect on transmission of S. mansoni in St Lucia. Nearby comparison settlements, in the same valley, were provided with water through a public standpipe system. The incidence of S. mansoni infection among children decreased in the experimental area, leading to lower prevalence rates and lower intensity of infection in all age groups. Over the study period, indices of infection increased in the comparison settlements, but by the end of the period development was making those settlements less suitable for comparison purposes and some reduction in transmission was occurring.The changes in human infection rates were reflected in the results of studies with sentinel snails. In the experimental area, infection rates gradually fell owing to reduced water contact and consequently less contamination of the river and its banks, and possibly to the gradual reduction in contamination potential of the community with reduced prevalence and intensity of infection. It is suggested that a piped water supply be considered as a method of schistosomiasis control, but that the cost should not be debited only to the control of this disease since a clean water supply has other medical and social benefits.