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Rise in Malaria Rates, Drug Resistance Tied to Climate

At AAAS, a researcher describes how treating more people for the mosquito-borne parasite could lead to more resistance to drugs



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CHICAGO—Warmer temperatures are at least partly to blame for a surge in malaria in East Africa and the increase in drug-resistant strains of the disease, according to a University of Michigan researcher.

The malaria parasite is highly sensitive to changes in temperature, and even subtle warming can dramatically increase populations of the mosquitoes that transmit the disease, said ecologist Mercedes Pascual.

Some scientists have argued that climate is not involved in the increasing highland epidemics. Instead, they say, adaptations in the parasite that make it resistant to antimalarial drugs are the key drivers.

But Pascual said that this "either-or" view is misguided and improperly lets global warming off the hook.

"I think that’s a useless discussion," she said.

More likely, Pascual said, the two work in tandem to an effect greater than the sum of their parts, with rising temperatures leading to faster development of drug resistance.

"The literature has this controversy of 'Is it climate or is it drug resistance?' and drug resistance is taken as evidence that we don’t need to invoke climate change," she added.

No research has shown this synergy, but Pascual said it makes theoretical sense.

By making conditions favorable for mosquitoes, "warmer temperatures increase transmission, so you’re going to increase the number of people you treat," she said.  And past research has shown a threshold at which treating more cases leads to a higher incidence of drug resistance, making the disease difficult to treat and contain.

Malaria kills 3,000 people each day in Africa, and outbreaks on the continent aren't limited to the eastern highlands. Climate change will cause the disease to migrate away from low latitudes, scientists say.  That could rid some areas of outbreaks, but could cause others in regions whose inhabitants haven't developed any immunity.

The specifics of how malaria's climate-forced migration will affect outbreaks are largely unknown, but it's already underway, said Christopher Thomas of Aberystwyth University in the U.K.

"It’s now," he said.  "The change isn’t coming at the end of the century—it's happening right now."

Douglas Fischer is editor of The Daily Climate. This article originally appeared at The Daily Climate, the climate change news source published by Environmental Health Sciences, a nonprofit media company.

 

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