Wednesday, April 24, 2013

Forest conservation could reduce malaria transmission

María Elena Hurtado in Preserving the biodiversity of tropical forests could have the added benefit of cutting the spread of malaria, according to a new study. The finding contradicts the traditional view that clearing native forest for agriculture curbs malaria transmission in the Amazon rainforest.

"Our study suggests, in contrast, that conservation of biodiversity can be reconciled with malaria control," Gabriel Zorello, an epidemiologist at Brazil's University of Sao Paulo and lead researcher of the study, tells SciDev.Net.

The researchers looked at two aspects that can affect malaria transmission in forested areas: the numbers of warm-blooded animals and the numbers of mosquitoes that do not carry malaria. Their study area was a large, sparsely-populated forested mountain range within the Atlantic Forest of southeastern Brazil. Warm-blooded animals live there, including medium-to-large birds such as toucans and quails, and mammals such as howler monkeys and squirrels.

No malaria cases have been reported on the mountain range in the past 30 years, but the primary malaria mosquito in the Atlantic Forest, Anopheles cruzii, lives nearby and could introduce the Plasmodium vivax parasite — associated with an estimated 80–300 million cases of malaria worldwide.

The researchers plugged real data from the area into a mathematical model of their own design to explore what would happen to malaria rates when the numbers of warm-blooded animals and non-malarial mosquitoes grew.

They found that the circulation of P. vivax is curbed when mosquitoes and animals are more abundant — suggesting that the mosquitoes compete with each other, and that the animals act as dead-end reservoirs of the malaria parasite. "These aspects of biodiversity that can hinder malaria transmission are services provided by the forest ecosystem," says Zorello....

Culex pipiens, shot by Alvesgaspar, Wikimedia Commons, under the Creative Commons Attribution-Share Alike 3.0 Unported license

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