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Eltahir Group predicts little adverse impact of climate change on malaria in West Africa

December 19, 2016 - 22:08 -- William Jobin

It is important to note a recent report on the predicted impact of climate change on malaria in West Africa, by Teresa K. Yamana, Arne Bomblies and Elfatih A. B. Eltahir. 2016 in the Journal Nature, entitled "Climate change unlikely to increase malaria burden in West Africa." doi:10.1038/nclimate3085

In the past, many reports on the impact of climate change on malaria transmission had been drawn using relatively simple biological models and statistical approaches, with inconsistent predictions. However in this report from the Eltahir Research Group at MIT in the US of America, the authors used a sophisticated computer simulation of climate and malaria transmission developed by the Eltahir Group to evaluate the impact of climate change specifically for West Africa.

The authors explained how their model simulates the way that malaria transmission is closely tied to climate. In West Africa, mosquito populations depend on the availability of water pools for breeding. The presence and persistence of these pools are tied to the region’s hydrology, as they are formed by excess rainfall and depleted by evaporation and infiltration into the ground. Temperature also plays an important role in malaria transmission, affecting the lifespan of the adult mosquito, the development rates of mosquito larvae, and the incubation period of the malaria parasite within the mosquito.

The authors used predictions of these climatic variables to look at how the environmental suitability for malaria transmission will change as temperatures rise and the distribution of rainfall is altered. They used a computer model named HYDREMATS to simulate transmission under current and future climates and identify areas that may be especially vulnerable to increases in transmission, as well as areas where transmission is expected to decrease.

In this report, they presented results from a decade-long study involving field observations and the sophisticated HYDREMATS model simulating village-scale transmission. They drove the malaria model with select climate models that correctly reproduce historical West African climate, and projected reduced malaria transmission. Their conclusion was that the impacts of climate change on malaria transmission in this region of Africa are not of serious concern.

Why would this be so? A simple explanation would be that wet season temperatures throughout West Africa currently approach or exceed the limits of mosquito survival, thus all future warming scenarios would lead to increased mosquito mortality, decreasing the transmission rate.

Projections using the HYDREMATS model to simulate other parts of Africa did not give these same conclusions however.

An important value of this model is that it can be used to evaluate alternative regional strategies for malaria suppression in the face of expected changes due to climate change.