Malacologic-schistosomal study of the refugee camps on the Plain of Ruzizi in the Democratic Republic of the Congo

Bilharziasis due to Schistosoma mansoni is widespread in the eastern part of the People's Republic of the Congo, particularly in the Ruzizi plain area. The intermediate host is the fresh-water snail Biomphalaria pfeifferi whose ecology is now well documented. Bilharziasis due to Schistosoma haematobium and Schistosoma intercalatum have not yet been observed but the potential for this development is high given the presence of the intermediate hosts, i.e. Bulinus truncatus, Bulinus globosus, and Bulinus forskalii, and the migration of populations in the area. Malacological and cercariometric studies were undertaken in 3 refugee camps in 1995. Findings showed that Biomphalaria pfeifferi was present in all water systems tested but that levels varied from 21 p. 100 to 70 p. 100 from one camp to another. The rate of infestation by Biomphalaria pfeifferi varied from 37 to 20 p. 100 depending on the sampling site. Given the prevalence of Schistosoma mansoni in the population, extension of bilharziasis is likely in the Ruzizi plain area and its surroundings. Potential intermediary hosts for Schistosoma haematobium and Schistosoma intercalatum were of lower relative prevalence and were found in specific biotopes. The authors propose methods of controlling water snails and preventing infection of people and water systems.