Distribution of Bulinus truncatus, the intermediate host of Schistosoma haematobium, in an irrigation system in Morocco

Bulinus truncatus, the intermediate snail host of Schistosoma haematobium, was widely distributed within the irrigation system at Tessaout-Amont area, located about 70 Km northeast of Marrakech. The lakes and the primary canals were not colonized, but secondary canals and especially various associated structures (syphon boxes, drop structures and weirs) were important habitats for B. truncatus. Bulinus truncatus is particularly abundant in tertiary canals, but it is there almost completely restricted to the syphon boxes as these canals, except for syphon boxes, dry out quickly when irrigation stops. The distribution of B. truncatus seems to be governed by irrigation practices in terms of water management, rather than by water physicochemical parameters or occurrence of aquatic plants.