FIELD-TESTS OF A VILLAGE-BASED MOLLUSCICIDING PROGRAM FOR THE CONTROLOF SNAIL HOSTS OF HUMAN SCHISTOSOMES IN CAMEROON

The feasibility of using unskilled workers at the district or village lever to perform mollusciciding activities in arid regions of northern Cameroon was investigated. A simplified procedure for application to temporary ponds, the principal sites of schistosomiasis transmission i n that region, was tested. This consisted of mixing the required quant itity of niclosamide (Bayluscide, Bayer AG, Leverkusen) with pond wate r in a plastic watering can and applying the mixture around the circum ference. To aid dispersion, the can was repeatedly swept from the peri meter toward the centre of the pond. Two ponds each were treated once near the end of the rainy season at 1 of 3 concentrations: 0.5, 1.0 an d 1.5 p.p.m. Following treatment, 100% snail mortality was recorded at all concentrations. A simple, rapid method for determining the quanti ty of niclosamide needed to treat temporary ponds was also devised. ph ysical characteristics were determined for 16 potential schistosomiasi s transmission sites in the region. An integration of those characteri stics was used to develop a simplified scale indicating the quantity o f niclosamide needed to treat ponds based on their circumference. The operational feasibility of a village based mollusciciding programme us ing those simplified procedures was then evaluated in 2 villages. Vill age health workers demonstrated a high accuracy (87%) in identifying p otential schistosomiasis transmission foci and snail host populations were virtually eliminated from treated sites.