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.