[Epidemiology of intestinal schistosomiasis with Schistosoma mansoni in Richard-Toll (Delta of the Senegal River). Malacological study].

A recent outbreak of intestinal schistosomiasis (1989) has been reported in Richard-Toll (Delta of Senegal River) with a global prevalence of 43%. A malacological survey has been carried in order to study, the density of Biomphalaria pfeifferi the intermediate hosts, their distribution and rate of infection, and to identify the transmission sites. Ten districts have been selected. The snails have been collected in the different water points of these localities which are the river, the Taouey marigot, the Taouey channel and the irrigation channels and drains of the CSS (Senegal Sugar Company). A total of 1,210 Biomphalaria have been collected in 45 sites with a variable density of 2 to 150 snails. The overall rate of infestation of snails is 44% but varies according to the districts (9 to 64%). The transmission is acting in all the districts mainly in the Taouey channel (28% of infested snails) the Taouey marigot (38% of infested snails) and particularly in the channels of CSS (47% of infested snails). The situation is alarming and requires urgent action be undertaken to decrease the prevalence and reduce the transmission.