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A study conducted by WLE showed that one million people living near
large dams in sub-Saharan Africa (SSA) are at risk of contracting
malaria each year, four times more than previously estimated.
The findings are particularly important because recent increased
aid for water resources development has prompted a new era of
dam building in the region. Scientists from IWMI and the University
of New England, Australia, estimated that the anticipated construction
of 78 major new dams in SSA would lead to 56,000 additional
malaria cases each year.
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Malaria is transmitted by the Anopheles mosquito, which breeds in slow-moving or stagnant water. The shallow puddles that form around the shorelines of dam reservoirs provide the perfect conditions for reproduction. So, building new dams has the potential to increase transmission levels and affect patterns of malaria infection. Small dams, as well as natural ponds, lakes and wetlands, also provide favorable mosquito breeding grounds. In total, around 174 million cases of malaria occur in SSA each year.
The scientists mapped the locations of 1,268 existing and 78 planned dams against the malaria stability index, which shows areas having no malaria, stable malaria or unstable (seasonal) malaria. They then used the Malaria Atlas Project (MAP) and WorldPop databases to determine the malaria infection rate at different distances from reservoirs. They found that a total of 15 million people living within 5 km of dam reservoirs are at risk of contracting the disease, and that 1.1 million malaria cases are linked to the presence of large dams each year.
Many African countries are currently planning the construction of dams, keen to reap the economic and development benefits that having reliable supplies of water for hydropower, irrigation and domestic use can bring. However, the report makes clear for the first time the extent to which malaria negatively affects those living nearby, and shows that these impacts are currently not being sufficiently offset by dam developers. Potential actions for mitigating the increased risk of malaria include designing and managing dam reservoirs to reduce mosquito breeding, introducing larvae-eating fish and distributing bed nets.
IWMI scientists Jonathan Lautze, Matthew McCartney and Luxon Nhamo (from the Institute’s Pretoria [South Africa] and Vientiane [Lao PDR] offices) collaborated on the study with biologists Solomon Kibret and Glenn Wilson from the University of New England, Australia. Following the publication of a peer-reviewed paper in the September 2015 issue of Malaria Journal, the report’s findings were further publicized by the Washington Post, CNN.com, BBC, Reuters, Voice of America (VOA), SciDev.Net, The Guardian (Nigeria), United Press International, Serious Science, Kenya’s Business Daily, OutbreakNewsToday.com and others.
