POPULATION BIOLOGY OF THE FRESH-WATER SNAIL BIOMPHALARIA-PFEIFFERI IN THE ZIMBABWE HIGHVELD

1. The population dynamics of Biomphalaria pfeifferi (Krauss), an intermediate host for intestinal schistosomiasis, were studied at four river sites in the Zimbabwe highveld for up to 28 months. 2. Adult snail abundances were monitored at weekly intervals using a fractional sampling method. 3. At two sites a mark-recapture method was used to estimate absolute abundances and recruitment and loss rates. 4. Seasonal variations in abundance were related to temperature and water flow. Mortality rate was not significantly influenced by temperature but recruitment rate increased over the range 13-24-degrees-C. 5. The geographic distribution of intestinal schistosomiasis in Zimbabwe reflects the distribution of warm temperature and permanent water bodies suitable for B. pfeifferi.