Climate change is impacting all of our lives and prompting new questions about what the future holds. For those on the frontlines of malaria – researchers, mothers and children in endemic areas, and health policymakers – the stakes could not be higher. They are faced with navigating a future in which the distribution of malaria could shift in unpredictable ways, complicating efforts to control the spread of mosquitoes, the parasite, and the disease.
Recent research, while still not definitive, provides a clearer picture, highlighting the complexity and regional variability of the impact of climate change on malaria and its vector.
The expanding range of African Anopheles mosquitoes
Using historical data from 1898 to 2016, researchers have been able to confirm that the geographic range of the malaria vector – Anopheles mosquito – has been expanding over the twentieth century. These mosquitoes have gained ground both in terms of latitude and elevation, particularly in highland and southern Africa, where areas once too cold for mosquitoes to thrive have now become more suitable.
Though the above findings align with the expectations of climate change impacts, there is still a need for further research that explores direct causality of climate change on the expansion of these malaria vectors.
Temperature’s myriad impact on malaria
Temperature has a complex and non-linear relationship with malaria transmission. Modelling predicts that malaria transmission is optimal at 25º C. Higher temperatures could in fact decrease transmission rates, offering some hope down the line for malaria-endemic regions in sub-Saharan Africa. However, other parts of the world are warming too, including places that were previously too cold for mosquitoes, presenting new opportunities for malaria vectors to thrive in new habitats.
In areas where malaria is already prevalent, warmer temperatures accelerate the growth cycle of the malaria parasite. Higher temperatures shorten the extrinsic incubation period, which is the time it takes for a mosquito to become infectious after feeding on infected blood, amplifying the spread of malaria. Moreover, high temperatures could also influence the efficacy of insecticides widely used in malaria control strategies, as seen in this laboratory study.
While the link between temperature and malaria is still being investigated, we are already observing numerous other impacts of climate change on this deadly disease.