Development of bait formulations for control of intermediate hosts of African schistosome species

Exploration of methods of snail control indicated a need for a new method because many failures in control programmes are due to lack of contact between molluscicides and the target snail population. The incorporation of molluscicides inside food pellets that are attractive to and ingestible by the target snails is suggested. Different concentrations of alcoholic extracts of Ambrosia maritima, Cucumis prophetarum and Rhynchosia minima-molluscicides of plant origin-were compared with niclosamide (Bayluscide) which is a strong synthetic molluscicide. They were incorporated into attractive food pellets and the lethal doses were determined. The results showed that Biomphalaria alexandrina snails are sensitive to only bait formulations with low concentrations of molluscicides. Laboratory and semi-field trials were conducted to study the efficacy of the prepared bait formulations on Biomphalaria alexandrina snails. The stability of these bait formulations was studied and it was observed that their effectiveness was reduced after long storage periods (> 3 weeks). The results revealed that Ambrosia maritima was the most effective molluscicide.