Executive Summary

This case study is about the effects dam building and land use change have had on schistosomiasis, a parasitic disease, in the Senegal River Basin in West Africa. Construction of the Diama Dam at the mouth of the Senegal River was intended to bring various human health and economic benefits. While there were some positive impacts, the dam also had unintended consequences. For one, it affected the life cycle of a native river prawn, hindering its essential migration to the mixed fresh and saltwater estuary near the Atlantic Ocean. An important predator in the river ecosystem, the local extinction of prawns led to an upstream explosion in the snail species that serve as a reservoir for schistosomiasis. Disease rates spiked and schistosomiasis has been endemic in Senegal since the dam was completed in 1986. As similar human infrastructure projects are proposed worldwide, it is key to understand the effect these developments could have not only on the environment but also on human health.

Past interventions addressing schistosomiasis have focused on the distribution of therapeutic drugs. These campaigns have been unsuccessful in countries like Senegal. One reason is because they fail to consider how social, ecological, economic, cultural, and health access factors affect the transmission of disease. A team of researchers and civilians called The Upstream Alliance are mindful of these complexities and the original ecosystem balance that kept snail populations in check. The group proposes reintroducing the native prawn species as an ecological intervention to complement drug therapy. This intervention has been found to reduce schistosomiasis rates and, if successful and sustainable, could provide food and livelihood security for people living in the Senegal River Basin.