Evaluation of three methods to control Bulinus truncatus, the intermediate host of Schistosoma haematobium in an irrigation scheme, Tessaout-Amont, Morocco

In Morocco, the implementation of new irrigation schemes resulted in the introduction of schistosomiasis haematobium to new areas. Canal structures (especially syphon boxes) were found to be favourable habitats for Bulinus truncatus and they constitute important transmission sites. Three methods for snail control in these syphon boxes were assessed in the Tessaout-Amont irrigation scheme. Molluscicide (niclosamide) application resulted in a pronounced reduction in the snail population density, but snails started to recolonise the sites a few months later. Regular brushing of the inner sides of the syphon boxes and covering the syphon boxes, so as to exclude light, resulted in significant reductions in snail numbers. However, the latter methods were not as efficient as the molluscicide.