[Impact of water resource installations on the distribution of schistosomiasis and its intermediary hosts in Burkina Faso].

Dams generally are a favourable biotope for the molluscs acting as intermediary hosts to schistosomiasis. The importance of the schistosomiasis endemic which follows depends on the interactions taking place between the parasites and their definitive (humans) and intermediary hosts. A preliminary sound knowledge of the prevailing epidemiological situations is therefore necessary to define an efficient programme to fight these infections. The extension of schistosomiasis following the installation of water resource facilities is significative of the part played by these hosts. In the hydroagricultural complex of Sourou, the prevalence of urinary schistosomiasis increased from 19% in 1954 to more than 70% in 1998-1999 in Guiédougou, the most ancient site. As to digestive schistosomiasis, almost unheard of until 1987, its prevalence ranged from 8% to 69% in 1998 in the villages located alongside the areas thus equipped. In the Kou Valley, the prevalence went up from 14% in 1957 to 80% in 1974 for urinary schistosomiasis and from 1.3% to 45% for intestinal schistosomiasis. The same tendencies are likely to appear in the hydraulic installations of Bagré, Ziga, and Kompienga. Dams thus constitute amplifying factors for the proliferation of species and for parasite-host interactions. All the actors (developers, populations and scientists) are faced with the challenge of finding a mean to control the development of schistosomiasis infections which are likely to seriously lessen the benefits expected from these hydraulic installations.