Time to revisit how dams are affecting malaria transmission
Authors: Solomon Kibret
Journal: The Lancet Planetary Health (2018)

Dams are widely recognised as a key factor in promoting economic growth, ensuring food security, alleviating poverty, and increasing resilience in the face of climate variability in sub-Saharan Africa.1Biswas AK Impact of large dams: issues, opportunities and constraints.in: Tortajada C Altinbilek D Biswas AK Water resources development and management: impact of large dams a global assessment. Springer, Spain2012Crossref Scopus (26) Google Scholar This region has the lowest per-capita water withdrawals in the world,2International Water Management InstituteDams and malaria in Africa: time for action. Colombo, Sri Lanka. IWMI Policy Brief 40.http://www.iwmi.cgiar.org/publications/briefs/water-policy-briefs/dams-and-malaria-in-africa-time-for-action/Date: 2018Date accessed: August 12, 2018Google Scholar which poses a crucial need to build dams to ensure water security for sustainable development. In this regard, hundreds of large dams are under construction to accelerate the region's economic development. However, dam construction could lead to negative public health consequences, such as malaria outbreaks, if not handled properly. Evidence on the effect of dams on malaria transmission in Africa is mounting. African dams have been shown to cause at least 1·1 million malaria cases each year.3Kibret S Lautze J McCartney M Wilson G Nhamo L Malaria impact of large dams in sub-Saharan Africa: maps, estimates and predictions.Malar J. 2015; 14: 339Crossref PubMed Scopus (35) Google Scholar However, this estimate is conservative, because the study included only 956 large dams out of more than 2000 dams existing in the region. The population at risk of malaria around these dams is estimated to be 15 million. This is projected to increase to 25–26 million by the 2050s as a result of population growth and climate change, and the number of malaria cases associated with reservoirs is projected to rise to 2·1–2·9 million in the 2050s.4Kibret S Lautze J McCartney M Nhamo L Wilson GG Malaria and large dams in sub-Saharan Africa: future impacts in a changing climate.Malar J. 2016; 15: 448Crossref PubMed Scopus (22) Google Scholar With hundreds of large dams under construction or planned, it is time to look critically at various measures that need to be taken to alleviate malaria around African dams. Numerous previous studies have shown that damming rivers slows down the water flow and creates large impoundments that provide ideal breeding habitats for malaria-causing mosquitoes.5Kibret S Wilson GG Ryder D Tekie H Petros B The influence of dams on malaria transmission in sub-Saharan Africa.EcoHealth. 2017; 14: 408-419Crossref PubMed Scopus (19) Google Scholar, 6Keiser J Castro MC Maltese MF et al.Effect of irrigation and large dams on the burden of malaria on a global and regional scale.Am J Trop Med Hyg. 2005; 72: 392-406Crossref PubMed Scopus (208) Google Scholar Communities living close to reservoirs are thus at greater risk of contracting malaria than those living further away. For example, in communities living close to the Koka dam of Ethiopia, malaria incidence is nearly 20-times higher than in those living more than 6 km away.6Keiser J Castro MC Maltese MF et al.Effect of irrigation and large dams on the burden of malaria on a global and regional scale.Am J Trop Med Hyg. 2005; 72: 392-406Crossref PubMed Scopus (208) Google Scholar This indicates how reservoir communities are facing possible negative public health effects of river damming. A study by Noriko Endo and Elfatih Eltahir, published in The Lancet Planetary Health, has found that locating people away from the reservoir shoreline could reduce malaria because wind speed and direction increases larval abundance in areas close to the reservoir compared with those that are further away.7Endo N Eltahir EA Prevention of malaria transmission around reservoirs: an observational and modelling study on the effect of wind direction and village location.Lancet Planet Health. 2018; 2: e406-e413Summary Full Text Full Text PDF PubMed Scopus (9) Google Scholar It is good to see researchers advising decision makers to relocate reservoir communities away from malaria risk zones. However, the question is whether it is possible. In water-stressed areas like sub-Saharan Africa, people tend to relocate closer to water infrastructures so that they can access water for domestic use and irrigation. Broadly, several issues should be considered before deciding where to place a dam, and how best to operate a dam after construction in order to mitigate negative social, environmental, and public health effects. Placing a dam in non-malaria-endemic areas is recommended, if it is possible. At the very least, a buffer zone should be put in place to avoid people living close to the dam, to minimise the risk of malaria. If a dam has to be placed in a malaria-endemic area, features should be put in place to render the shoreline areas less favourable for mosquito breeding. A study indicated that a faster water level drawdown desiccates mosquito larval habitats before the larvae complete their aquatic stage.8Kibret S Wilson GG Ryder D Tekie H Petros B Can water-level management reduce malaria mosquito abundance around large dams in sub-Saharan Africa?.PloS One. 2018; 13: e0196064Crossref PubMed Scopus (9) Google Scholar Such manipulation of the water level by optimising the reservoir management worked well to control malaria when used by the Tennessee Valley Authority in the USA.9Kitchens C A dam problem: TVA's fight against malaria, 1926–1951.J Econ Hist. 2013; 73: 694-724Crossref Scopus (21) Google Scholar Overall, the effect of dams on malaria in African settings needs to be revisited, because the region is striving for malaria control and elimination. Proper measures need to be taken to address the malaria risk around such economically important, large infrastructures. By either placing people away from the dam-related malaria risk area or through use of optimised water level management, reservoir communities in Africa should be able to avoid the negative consequences of dams. Enhancing malaria control and prevention measures around dams should also help to contain transmission in communities living at close proximity to dams. People deserve to enjoy the economic benefits of dams without being subjected to malaria risks. As Africa will be building many dams in the near future, malaria should not remain a forgotten public health challenge for the communities living close to large water reservoirs. I declare no competing interests. Prevention of malaria transmission around reservoirs: an observational and modelling study on the effect of wind direction and village locationThe effect of wind on malaria transmission around reservoirs can be substantial. The transmission of malaria can be minimised if the location of villages situated near a reservoir is carefully considered. For areas in which the environmental conditions surrounding a resevoir are equal, villages should be located downwind of reservoirs to reduce the incidence of malaria, although further research will be required in locations where wind direction changes in different seasons. Full-Text PDF Open Access