Field trials to control schistosome intermediate hosts by the plant molluscicide Ambrosia maritima L. in the Senegal River Basin.

Several field experiments were carried out in Senegal to evaluate the molluscicidal activity of Ambrosia maritima L. Applications of 400 mg L-1 of dry leaves of the plant in creeks of the Lampsar river did result in a reduction of Bulinus spp of 54-56% 2 weeks after treatment. Treatment of a closed irrigation canal caused a reduction of the density of Biomphalaria pfeifferi up to 77% 2 weeks after the application of 150 mg L-1 and 300 mg L-1. In both trials, however, a quick increase in the snail density was observed after treatment. It is concluded that the large amounts of crude plant material required to achieve snail reductions of less than 80% compromise the use of A. maritima in schistosomiasis control programmes.