Malaria impact of African dams7 March 2016
New research claims that African dams are linked to over one million Malaria cases annually. Developers of future dam projects are being urged to consider better disease control measures. Furthermore, communication between water and health communities should be improved in order to address Malaria while planning, designing and operating African dams.
Over one million people in sub-Saharan Africa will contract malaria in 2015 because they live near a large dam, according to claims by a new study which, for the first time, has correlated the location of large dams with the incidence of malaria and quantified impacts across the region. The study finds that construction of an expected 78 major new dams in sub-Saharan Africa over the next few years will lead to an additional 56,000 malaria cases annually.
"Dams are at the centre of much development planning in Africa. While dams clearly bring many benefits -- contributing to economic growth, poverty alleviation and food security -- adverse malaria impacts need to be addressed or they will undermine the sustainability of Africa's drive for development," said biologist Solomon Kibret of the University of New England in Australia, the paper's lead author.
Undertaken as part of the CGIAR Research Programme on Water, Land and Ecosystems, the study was published in Malaria Journal and looked at 1268 dams in sub-Saharan Africa. Of these, just under two-thirds, or 723, are in malarious areas. The researchers compared detailed maps of malaria incidence with the dam sites. The number of annual malaria cases associated with the dams was estimated by comparing the difference in the number of cases for communities less than 5km from the dam reservoir with those for communities further away.
The researchers found that a total of 15M people live within 5km of dam reservoirs and claim they are at risk, and that at least 1.1M malaria cases annually are linked to the presence of the dams.
"Our study showed that the population at risk of malaria around dams is at least four times greater than previously estimated," said Kibret, noting that the authors were conservative in all their analyses.
The risk is particularly high in areas of sub-Saharan Africa with "unstable" malaria transmission, where malaria is seasonal. The study indicated that the impact of dams on malaria in unstable areas could either lead to intensified malaria transmission or change the nature of transmission from seasonal to perennial.
Previous research has identified increased malarial incidence near major sub-Saharan dams such as the Akosombo Dam in Ghana, the Koka Dam in Ethiopia and the Kamburu Dam in Kenya. But until now, no attempt has been made to assess the cumulative effect of large dam building on malaria.
Slow moving water
Malaria is transmitted by the Anopheles mosquito, which needs slow-moving or stagnant water in which to breed. Dam reservoirs, particularly shallow puddles that often form along shorelines, provide a perfect environment for the insects to multiply. Thus dam construction can intensify transmission and shift patterns of malaria infection. Many other water bodies, including small dams, ponds and natural lakes and wetlands, provide breeding habitat for mosquitoes. In total, there are an estimated 174M cases of malaria in sub-Saharan Africa per year.
Many African countries are planning new dams to help drive economic growth and increase water security. And although they agree that improved water storage, irrigation and hydropower generation are indeed badly needed for growing populations in this fast developing continent, the researchers warn that building new dams has potential costs as well as benefits.
"Dams are an important option for governments anxious to develop," said Matthew McCartney of the International Water Management Institute (IWMI) and a co-author of the paper. "But it is unethical that people living close to them pay the price of that development through increased suffering and, possibly in extreme cases, loss of life due to disease."
The study claims that despite growing evidence of the impact of dams on malaria, there is scant evidence of their negative impacts being fully offset.
The authors make recommendations about how the increased malaria risk can be managed. Dam reservoirs could be more effectively designed and managed to reduce mosquito breeding. For instance, one option is to adopt operating schedules that, at critical times, dry out shoreline areas where mosquitoes tend to breed. Dam developers should also consider increasing investment in integrated malaria intervention programmes that include measures such as bed net distribution. Other environmental controls, such as introducing fish that eat mosquito larva in dam reservoirs, could also help reduce malaria cases in some instances.
"The bottom line is that adverse malaria impacts of dams routinely receive recognition in Environmental Impact Assessments, and areas around dams are frequently earmarked for intensive control efforts. The findings of our work hammer home the reality that this recognition and effort -- well-intentioned though it may be -- is simply not sufficient," said co-author Jonathan Lautze, a researcher at the International Water Management Institute's office in Pretoria, South Africa. "Given the need for water resources development in Africa, malaria control around dams requires interdisciplinary cooperation, particularly between water and health communities. Malaria must be addressed while planning, designing and operating African dams."
Malaria impact of large dams in sub-Saharan Africa: maps, estimates and predictions by Solomon Kibret, Jonathan Lautze, Matthew McCartney, G. Glenn Wilson and Luxon Nhamo. Malaria Journal 2015. 14 (1) DOI: 10.1186/s12936-015-0873-2
The lead author can be contact at the University of New England in Australia. Email: [email protected]