The study published in Climatic Change last month (19 June), says research on malaria predictions that use global climate change simulation fail to show impacts at specific locations.
To determine how future climate change would affect malaria transmission in four locations in Kenya — the cool upland areas of Kericho and Kitale, the warm lower altitude site of Kisumu and the hot savannah-like environment of Garissa — the researchers downscaled projections made by conventional low-resolution climate models.
They evaluated the potential of malaria transmission across the four sites for 1981-2000 and 2046-2065 using both the conventional and downscaled or high-resolution models.
“It can cause an epidemic because populations in these areas do not have natural immunity that is developed over time by those who live in malaria endemic areas.”
Walter Otieno, Kenya Medical Research Institute and Centers for Disease Control and Prevention
The results predicted an upsurge of future transmission potential in the cooler sites of Kericho and Kitale due to temperature rises.
According to the study, whereas mean malaria transmission potential using a conventional model is expected to increase by 72 per cent in 2046-2065 compared with 1981-2000 in Kericho, the corresponding figure for a downscaled model is 1,800 per cent increase.
The US and Spain-based researchers, however, noted a reduction in hot environments: Garissa. “This area is already at or beyond the temperatures optimum for transmission. So any further temperature increase will lower the risk”.
They also predicted a modest increase in malaria transmission in Kisumu due to rising temperatures.
Matthew Thomas, a co-author of the study and a professor in ecological entomology at Penn State University, United States, says higher resolution estimates offer results that are tailored to local conditions and enables better capturing of temperature variations.
Krijn Paaijmans, the study’s lead author and an assistant professor at the Barcelona Centre for International Health Research, Spain, says temperature is one of the important factors affecting the spread of malaria.
“As it increases, mosquitoes and the malaria parasites they carry develop faster. They also feed more frequently and their populations grow faster,” Paaijmans explains, noting that all these traits have an optimum. “So when temperatures get too high, things slow down again.”
Walter Otieno, a malaria researcher at the Kenya Medical Research Institute and Centers for Disease Control and Prevention, warns of dire consequences if malaria transmission suddenly increases in highland areas with traditionally low prevalence rates.
“It can cause an epidemic because populations in these areas do not have natural immunity that is developed over time by those who live in malaria endemic areas such as Kisumu,” says Otieno.
He notes that malaria interventions such as use of insecticide-treated bednets need to be rolled out in these areas to cut transmission.
According to the WHO, major killers including malaria and dengue fever, both transmitted by mosquitoes, are climate-sensitive and could worsen with climate change.
This article has been produced by SciDev.Net's Sub-Saharan Africa desk.