Field tests of a village-based mollusciciding programme for the control of snail hosts of human schistosomes in Cameroon.

The feasibility of using unskilled workers at the district or village level 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 in that region, was tested. This consisted of mixing the required quantity of niclosamide (Bayluscide, Bayer AG, Leverkusen) with pond water in a plastic watering can and applying the mixture around the circumference. To aid dispersion, the can was repeatedly swept from the perimeter 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 and 1.5 p.p.m. Following treatment, 100% snail mortality was recorded at all concentrations. A simple, rapid method for determining the quantity of niclosamide needed to treat temporary ponds was also devised. Physical characteristics were determined for 16 potential schistosomiasis transmission sites in the region. An integration of those characteristics was used to develop a simplified scale indicating the quantity of niclosamide needed to treat ponds based on their circumference. The operational feasibility of a village based mollusciciding programme using those simplified procedures was then evaluated in 2 villages. Village health workers demonstrated a high accuracy (87%) in identifying potential schistosomiasis transmission foci and snail host populations were virtually eliminated from treated sites.