Observations on the compatibility between Bulinus spp. and Schistosoma haematobium in the Senegal River basin

Snail-infection experiments were carried out with a number of different spe cies and populations of Bulinus and isolates of Schistosoma haematobium. Th e parasites came from six localities in the Senegal River basin (SRB), in t he Lower Valley (Mbodiene), Middle Valley (Podor, Diatar and Nguidjilone), and Upper Valley (Aroundou and Gallade). Isolates of S. haematobium from th e Middle and Upper Valleys all showed some compatibility with laboratory-br ed B. truncatus from Mall, but none of these isolates was compatible with l aboratory-bred B. truncatus originating from Senegal. Schistosoma haematobi um from Diatar (Middle Valley) was compatible with B. senegalensis, whereas S. haematobium from Mbodiene (Lower Valley), which is naturally transmitte d by B. globosus, was incompatible with B. senegalensis and B. truncatus. T hese data demonstrate that different isolates of S. haematobium from differ ent regions of the SRB exhibit distinct intermediate-host specificities, wh ich in turn will have an effect on the epidemiology of the disease, includi ng the periods of transmission. It is apparent that, in addition to B. sene galensis and B. globosus, B. truncatus, the most widespread bulinid snail i n the SRB, may be playing a role in the epidemiology of urinary schistosomi asis. This conclusion has obvious implications for the future spread of uri nary schistosomiasis in the SRB. Chemical and physical measurements from assorted habitats along the SRB, in cluding pH, temperature, salinity, conductivity, and resistivity, are also reported.