INTERACTION BETWEEN BULINUS GLOBOSUS AND CLEOPATRA FERRUGINEA AT A TRANSMISSION SITE OF SCHISTOSOMIASIS IN KWALE, KENYA

Snail survey data collected in a srnall village in Kenya from April 1984 to March 1991 were used to analyze the interaction between Bulipu,is globosus (intermediate host of Schistosoma haematobium) and Cleopatra ferruginea (unsusceptible snaiD. An inverse correlation was observed between the two snail populations. This finding leads to the suggestion that C. fern,lginea has limiting effects on B. globosus population. The relative penetrative activity of S. haematobium miracidia into the two snail species was also examined. Miracidia penetrated C. ferruginea as well as B. globosus. Although selective mass-chemother- apy has been repeated every 2 years in our study area, the low infection rates in B. globosl,ts were recorded in the year when large numbers of C. ferruginea and small numbers of B. globosus were collected. Therefore, C. ferruginea seems to diminish the transmission of S. haematobium; C. ferruginea reduc~The number of S. haematobium miracidia which reach to B. globosus.