In the tropical highlands of South America and East Africa, cool temperatures have historically kept mosquito-borne diseases, such as malaria, at bay. New research by Howard Hughes Medical Institute (HHMI) scientists shows that as annual temperatures rise in these areas, malaria can spread to populations in higher elevations that had historically not been at as much risk of being infected by malaria parasites.
HHMI scientists have compared the yearly distribution of malaria cases in two mountainous regions in South America and East Africa, and found that in warmer years, populations at high elevations experience more infections than they do in cooler years. Their findings, published March 7, 2014, in the journal Science, suggest that without increased control measures, climate change will increase the burden of malaria, particularly in areas that are densely populated at higher elevations.
"The pattern is very clear, and the implication is that warmer temperatures cause an expansion in altitudes [where malaria infections occur]," says Mercedes Pascual, an HHMI investigator at the University of Michigan who led the study. "Long-term trends should see an increase in cases as the disease both expands to higher altitude and causes more cases at higher altitudes."
Temperature has long been known to affect the spread of malaria. The mosquito that transmits the malaria-causing parasites, Plasmodium falciparum and Plasmodium vivax, thrives at warmer temperatures. Furthermore, the parasite itself matures into its infectious form more rapidly when temperatures are high. Still, Pascual says, scientists have lacked direct evidence that increasing temperatures would permit the parasite to encroach on new territory. Some scientists have also argued that socioeconomic change and associated control measures might outweigh the effects of climate change.
Malaria prevalence fluctuates over time in response to many facto
|Contact: Jim Keeley|
Howard Hughes Medical Institute