[The distribution of freshwater molluscs the intermediate hosts of human schistosomas in Katan, south-Kivu].

In eastern Democratic Republic of Congo, the prevalence of bilharziasis due to Schistosoma mansoni is high along the Kivu lake shoreline where Biomphalaria pfeifferi, i.e. the intermediate host of Schistosoma mansoni, is the only snail that has been described until now. Although their occurrence has not been reported in the area, other schistosomas remain possible since their intermediate hosts are present. This study was carried out in 1992 to determine the distribution of intermediate host snails in freshwater systems in the region. Samples were collected according to the standardized harvest time unit method. Five species of intermediate host snails for human schistosomiasis were identified. By far the most prevalent species was Biomphalaria pfeifferi which was found in 75% of the freshwater systems studied. Given the presence of Schistosoma mansoni in the region, spread of this type of schistosome is likely. Ferrissia burnipi, the recognized intermediate host of Schistosoma haematobium, was observed in association with Biomphalaria pfeifferi. Snails of the Bulinus genus were confined to special environments. Factors preventing infestation by Schistosoma haematobium and Schistosoma intercalatum remain unclear. Control measures against snails and their larvae in fresh water systems in the region are needed to stop the spread of Schistosoma mansoni and prevent the appearance of Schistosoma haematobium and Schistosoma intercalutum.