[Parasitological profile of urinary schistosomiasis of the Sourou hydroagricultural complex of Burkina Faso].

In the Sourou area of Burkina Faso, parasitological and malacological surveys of urinary schistosomiasis have been carried out in the constructed sites of Guédougou, Niasan and Débé dating respectively from 1967, 1986 and 1996. The investigations covered also the traditional villages of Lanfiera, Di, Poro, Tiao and Mara situated in the middle of the hydroagricultural planning for the first, very close to the lake for the second and about twenty kilometres distant for the three last. These towns represent the main sites in the Sourou area. The results of the parasitological surveys showed that urinary schistosomiasis was present in all sites. The levels of prevalence varied considerably: 70.3% in Guiédougou, 40.8% in Niassan, 8.5% in Débè in the irrigated zone, 55.6% in Lanfiéra, 56.8% in Di, 13.2% in Poro, 83.3% in Tiao and 64.7% in Mara. Concerning the malacological investigation, two species (Bulinus senegalensis and B. truncatus) were shown to be intermediate hosts of Schistosoma haematobium. The first was endemic to the area while the second was compatible with S. haematobium from the Sourou and other zones. Compared to the results of earlier investigations, the endemic had worsened with differences according to sites. This disparity of prevalence levels which has already been observed in other hydroagricultural area results from many factors, among which the impact of irrigation activities, the aquatic biotope system (irrigation canals, natural lake, pools and temporary rivers) and the type of contact of human communities with water rank high. Schistosomiasis expansion is amplified by the intermediate host dynamics and the introduction of new schistosomes carried by the new workers arriving from all over the country. In these conditions, in order to reduce rapidly prevalence levels, preventive measures should be centred on chemotherapy for the population. The treatment should be administered during a period of weak intermediate host density and be directed towards in-coming workers. Such an approach should be able to check the spread of schistosomiasis naturally occurring with the irrigation of new sites.