[Population dynamics and infestation of Bulinus truncatus and Bulinus forskalii by schistosomal larvae in the Sudan-Sahelian zone of Cameroon].

The evolution of the population densities of Bulinus truncatus and Bulinus forskalii has been studied during 18 months in a number of sites of the Sudan-Sahelian zone of Cameroon, in relation to certain environmental factors. Only the altitude of the water in the sites has an influence on the density of the snails. The populations of B. truncatus present a greater proportion of young molluscs during the entire year, with the exception of the last months of the dry season. The population dynamics of B. forskalii varies depending on whether the environment is temporarily stagnant, temporarily running or stable. The proportions of B. truncatus and B. forskalii that emit cercariae of schistosomes are 1.2% and 0.8% respectively. Study of the adult worms obtained after infestation of the laboratory mammals show that B. truncatus emits cercariae of Schistosoma haematobium at the end of the dry season and at the beginning of the rainy season. We have not been able to identify precisely the cercariae emitted by B. forskalii, which raises the necessity of further systematic studies being carried out on the schistosomes of Cameroon.