Urinary schistosomiasis in the Sahelian region of the Senegal River Basin.

Two dams are projected for the Senegal River, West Africa, for hydroelectric power, anti-salt intrusion and for provision of a dependable supply of freshwater year-round. This study was to ascertain the geographic distribution of schistosomiasis, its snail hosts and the potential transmission sites before the construction of the two dams. No intestinal schistosomiasis was found in the area investigated, the Sahelian region. Villages in the delta, as well as those situated by the Senegal River in the Middle Valley were found free of urinary schistosomiasis. However, the prevalence of the urinary form averaged 10.4% in villages situated in the higher land away from the river. The transmission sites in these villages are rain-fed, laterite pools which harbor the snail host, Bulinus senegalensis. In one pond the latter was found naturally infected with schistosome cercariae, and there are no bovines or ovines in the area at any time. Other bulinid snails found infected with schistosome cercariae were B. guernei and B. jousseaumei; the latter is probably the snail host of Schistosoma haematobium in one small village in the delta, where a low infection rate was reported by other workers.