African dams contribute to over 1 million malaria cases every year

In September the Malaria Journal published an article called “Malaria impact of large dams in sub-Saharan Africa: maps, estimates and predictions.” We asked one of the authors, Solomon Kibret from the University of New England, to comment on this study.

The Study

In this study we investigated the impact of existing and planned large dams on malaria across sub-Saharan Africa. Dams with georeferenced locations were mapped in relation to malaria stability. The population at risk of malaria was estimated and the magnitude of malaria infection rate at different distances from the dam reservoirs analysed. Finally, the contribution of these dams to themalaria burden in the region was determined.

Data on annual malaria infection rates and population were gathered for a total of 1268 existing dams and 78 planned dams across sub-Saharan Africa. We mapped the distribution of dams and malaria and analyzed across the region. We quantified the number of malaria cases attributable to dams in communities living within 5 km from them. We validated our results with data from literature.

Our results showed that of the 1268 existing dams, 723 (57%) are located in malarious areas. Currently, about 15 million people live in close proximity (<5 km) to the reservoirs associated with these dams. A total of 1.1 million malaria cases annually are associated with them. Of the 78 planned dams, 60 will be located in malarious areas and these will create an additional 56,000 cases annually.

Background

Despite its vast freshwaters, the sub Saharan Africa is the least developed in terms of water infrastructures. The region’s population is set to double by 2050, with highest population growth in the world – which seriously faced the challenge of feeding its people. To address pressing challenges related to food security and increasing demands for economic development, the region has, in recent years, experienced a new era of large dam construction. However, despite their tremendous benefits, the link between dams and malaria has been a serious public health concern.

Malaria is a mosquito-borne disease that kills approximately 627,000 people every year globally – mostly children under the age of five. Over 80% of the global malaria burden occurs in sub-Saharan Africa. 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.

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In Africa, dams frequently increase malaria by creating shallow shorelines suitable for breeding of malaria-transmitting mosquitoes. Previous studies around the Koka dam in Ethiopia, the Akosombo Dam in Ghana and the Kamburi Dam in Kenya indicated that malaria increased following dam construction. Although data exists for few individual dams here and there, the cumulative impact of dams on malaria burden across the region was not quantified before. Our study is the first to quantify the impact of large dams on malaria in sub-Saharan Africa. We believed that understanding the cumulative impact of existing dams and assessing the potential effect of planned dams across the region helps allocate appropriate resources for disease interventions.

Future Directions

The study warns that dams contribute significantly to malaria risk in sub-Saharan Africa particularly in areas where the disease is seasonal. Additional malaria control measures are thus required to reduce the impact of dams on malaria. Dam decision makers should consider malaria risk while planning and designing a dam in the region.
The study also makes recommendations about how the increased malarial risk can be managed. Dam reservoirs could be more effectively designed and managed to reduce mosquito breeding. For instance, one option is to adopt dam operating schedules that dry shoreline areas where mosquitoes tend to breed, at critical times. Dam developers should also consider increasing investment in integrated malaria intervention programs that include measures such as bed net distribution.

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Dams are an important option for governments anxious to develop. But 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. The bottom line is that adverse malaria impacts of dams should routinely receive recognition and follow-up in Environmental Impact Assessments, and areas around dams frequently earmarked for intensive control efforts. The findings of our work hammer home the reality that current recognition and efforts is simply not sufficient. Given the need for water resources development in Africa, malaria control around dams requires interdisciplinary cooperation, particularly between water and health communities.