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Abstract:
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"This research report discusses ecological aspects of schistosomiasis transmission and options for its control in irrigated areas in Africa through environmental measures. Human schistosomiasis is endemic in 46 African countries. After being infected by larvae emerging from human excreta and urine deposited in the water, freshwater snails act as intermediate hosts. They, in turn, produce larvae that enter through the skin of people who are exposed to the contaminated water. Many surface irrigation systems in Africa create favorable snail-breeding conditions that facilitate the transmission of schistosomiasis. This process is illustrated with examples from different agro-ecological regions, including Morocco, Mali, Sudan, Cameroon, Egypt, Burkina Faso, Kenya and Zimbabwe. The presence and density of snails differ much among sites and vary within irrigated areas and over seasons, often subject to local circumstances, for example, inadequate water management and system maintenance that result in water stagnation and weed growing. These are common features in African irrigation systems along with increased human population densities and lack of sanitation and domestic water supply. Snail-control can be an important component of integrated campaigns against schistosomiasis transmission. Chemicals (molluscicides) can be effective in the control of snails on the short term, but not as a long-term measure as they are too expensive, eco-toxic and unsustainable. Environmental control of schistosomes' intermediate hosts (freshwater snails) offers good alternative approaches, especially when they reduce man-water contact as well. The main options available are adapted system design, adequate water management and proper maintenance."
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