Climate change effect increases malaria threat

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The number of Africans at risk of malaria who live near dams will nearly double to 25m by 2080, due to climate change, The Times reports.

Without prevention measures, the number of malaria cases associated with dams could triple to nearly 3m a year over the same period, they said in a study.

“While dams clearly bring many benefits … the role of climate change on malaria around dams will fundamentally alter the current impact,” said Solomon Kibret of the programme in public health, University of California Irvine and the paper’s lead author. “Accurately predicting the impacts of such changes is critical to planning effective disease control,” he said.

The report says malaria is transmitted by mosquitoes, which breed in stagnant water such as shallow puddles along dam shorelines. The disease kills around 400,000 people a year, the vast majority of them children and babies in sub-Saharan Africa. World Health Organisation data show there are around 200m malaria cases a year.

More than half of dams that are located in malaria-free areas that will turn into transmission zones as temperatures rise due to climate change are mainly found in the east African highlands and southern Africa, the study said. In those regions the impact of dams may be especially harsh because of lower immunity among people who have not had to deal with the disease before, it said.

The report says Africa is experiencing a surge in dam construction so as to generate electricity, irrigate crops and store water for fast-growing populations. Dams should be designed and managed to minimise the breeding of mosquitoes, such as periodically drying out shoreline areas or introducing fish that eat mosquito larva in reservoirs, said the study.

Background: Sub-Saharan Africa (SSA) has embarked on a new era of dam building to improve food security and promote economic development. Nonetheless, the future impacts of dams on malaria transmission are poorly understood and seldom investigated in the context of climate and demographic change.
Methods: The distribution of malaria in the vicinity of 1268 existing dams in SSA was mapped under the Intergovernmental Panel on Climate Change (IPCC) representative concentration pathways (RCP) 2.6 and 8.5. Population projections and malaria incidence estimates were used to compute population at risk of malaria in both RCPs. Assuming no change in socio-economic interventions that may mitigate impacts, the change in malaria stability and malaria burden in the vicinity of the dams was calculated for the two RCPs through to the 2080s. Results were compared against the 2010 baseline. The annual number of malaria cases associated with dams and climate change was determined for each of the RCPs.
Results: The number of dams located in malarious areas is projected to increase in both RCPs. Population growth will add to the risk of transmission. The population at risk of malaria around existing dams and associated reservoirs, is estimated to increase from 15 million in 2010 to 21–23 million in the 2020s, 25–26 million in the 2050s and 28–29 million in the 2080s, depending on RCP. The number of malaria cases associated with dams in malarious areas is expected to increase from 1.1 million in 2010 to 1.2–1.6 million in the 2020s, 2.1–3.0 million in the 2050s and 2.4–3.0 million in the 2080s depending on RCP. The number of cases will always be higher in RCP 8.5 than RCP 2.6.
Conclusion: In the absence of changes in other factors that affect transmission (e.g., socio-economic), the impact of dams on malaria in SSA will be significantly exacerbated by climate change and increases in population. Areas without malaria transmission at present, which will transition to regions of unstable transmission, may be worst affected. Modifying conventional water management frameworks to improve malaria control, holds the potential to mitigate some of this increase and should be more actively implemented.

Solomon Kibret, Jonathan Lautze, Matthew McCartney, Luxon Nhamo, G Glen Wilson

Full report in The Times
Malaria Journal abstract

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