Dynamique de transmission des schistosomes par Biomphalaria pfeifferi dans la région de Man, Côte d'Ivoire Dynamic transmission of Schistosoma by Biomphalaria pfeifferi in the region of Man in Côte d'Ivoire

Intestinal schistosomiasis by Schistosoma mansoni is a parasitary affection transmitted in West Africa by the mollusc Biomphalaria pfeifferi. Transmission dynamic of schistosomiasis by Biomphalaria pfeifferi has seldom been investigated in Cote d'Ivoire. In the framework of a research project on the epidemiology of schistosomiasis in the natural forest ecosystems, this study was performed longitudinally over a period of three years in Man region, in western Cote d'Ivoire. The trial set up from 1986 to 1989 and the project was funded by the World Health Organization. The general objective is to design a strategy of schistosomiasis control based on chemotherapy. The approach aims at interrupting or considerably reducing the reinfections, prolonging in that way the duration of the positive effects of the chemotherapy. The specific objectives assigned to the work consisted in studying the dynamic of the B. pfeifferi population and the infection of B. pfeifferi. To achieve our objectives, diverse methods (i: the molluscs sampling by two prospectors during 15 minutes per study site and ii: individual isolation of mol- luscs in test tubes with 5 or 10 mL of filtered water and exposure to light) have been used. They enabled us in the sampling of the intermediary host molluscs of Schistosoma and seek their infections. The results show that apparent high densities of B. pfeifferi can be observed at the end of the dry season and at the beginning of rainy seasons. In addition, the variation of relative abundance of intermediary host mol- luscs of Schistosoma is significantly influenced by rainfall and the system of water ways. The period of transmission of the infection to man is six months at Gueupleu village and ten months at Botonguine village. In order to optimize the effect of chemotherapy in these sites of transmission charac- terized by a high level of endemy (68 %), an extreme mobi- lity of human populations and a multiplicity of contamina- tion sites, this study should not only take into account the geographic space of the illness, but also it should eventually associate with a molluscicide action and/or a sanitary educa- tion through the teaching of primary health care.