Quantified at more than a million malaria cases each year
Large dams are a key contributor to economic growth, ensuring food security, alleviating poverty and resilience in the face of climate variability and change in sub-Saharan Africa. However, large dams frequently intensify malaria transmission – a mosquito-borne disease that globally kills approximately 627,000 people every year, mostly African children under the age of five.
In total, there are an estimated 174 million cases of malaria in sub-Saharan Africa annually. The disease also decreases productivity and increases the risk of poverty for the communities and countries affected. As a result, malaria causes economic losses in the region of over 12 billion US dollars (equivalent to 1.3% of total GDP) every year.
In Africa, the shores of many water reservoirs provide ideal breeding habitat for malaria transmitting mosquitoes. Many other water bodies in small dams, ponds and natural lakes and wetlands, also provide breeding habitat for mosquitoes.
New research by a team from the International Water Management Institute (IWMI) and the University of New England quantified the total malaria impact of large dams in sub-Saharan Africa. The locations of more than 1270 dams were mapped in relation to areas of stable (i.e. year-round) and unstable (i.e. seasonal) malaria transmission. The population at risk of malaria in these two epidemiological settings was estimated and the contribution of the dams to the malaria burden was determined. The impact of planned, not yet built, dams was also determined.
The research found that approximately 15 million people live within 5km of large dams and more than 1.1 million cases of malaria annually are associated with these dams. Current planned dams are likely to contribute an additional 56,000 cases annually. These numbers are conservative estimates because the locations of many more (perhaps 800) large dams in sub Saharan Africa are not recorded.
Who pays the price?
Current investment in large dams in sub-Saharan Africa is increasing to respond to the need for urgent economic development. Results of the present study call for intensive measures to mitigate malaria in the vicinity of the reservoirs created by existing and planned large dams. Whilst recognizing the importance of dams for economic development, it is unethical that people living close to them pay the price of that development through increased suffering and, in extreme cases, loss of life due to disease.
Water managers and development planners must invest in malaria control measures so that this adverse impact does not confound the larger aims that dams are built to achieve. Intensive malaria intervention efforts are particularly required in areas of unstable, less intense transmission where malaria impact of dams is the highest. Future investigation should look for additional cost-effective disease intervention tools such as reservoir management to help supplement the existing costly conventional malaria control measures.
There are many barriers to successful implementation of malaria control measures in the vicinity of large dams. A key question is how can dam builders and operators, be encouraged to work with relevant government agencies to mitigate the public health threats, not just malaria, that large dams pose?
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