MADISON Establishing a firm link between environmental change and human disease has always been an iffy proposition.
Now, however, a team of scientists from the University of Wisconsin-Madison, writing in the current (June 16, 2010) online issue of the CDC journal Emerging Infectious Diseases, presents the most enumerated case to date linking increased incidence of malaria to land-use practices in the Amazon.
The report, which combines detailed information on the incidence of malaria in 54 Brazilian health districts and high-resolution satellite imagery of the extent of logging in the Amazon forest, shows that clearing tropical forest landscapes boosts the incidence of malaria by nearly 50 percent.
"It appears that deforestation is one of the initial ecological factors that can trigger a malaria epidemic," says Sarah Olson, the lead author of the new report and a postdoctoral fellow at the Nelson Institute, Center for Sustainability and the Global Environment.
The clearing of tropical forests, say Olson and senior author Jonathan Patz of the University of Wisconsin School of Medicine and Public Health, creates conditions that favor malaria's primary carrier in the Amazon, the mosquito Anopheles darlingi, which transmits the malaria parasite if it draws its blood meals from infected humans.
"The deforested landscape, with more open spaces and partially sunlit pools of water, appears to provide ideal habitat for this mosquito," Olson says, noting that Anopheles darlingi has been shown to displace other types of mosquitoes that prefer forest and that are far less prone to transmit malaria.
"This study of human malaria cases complements our previous work that focused more on the abundance of the malaria-carrying mosquito," Patz adds. "In those studies from the Peruvian Amazon, we showed a correlation between this mosquito's larvae and aquatic breeding sites in disturbed habitats following land clearance."
|Contact: Jonathan Patz|
University of Wisconsin-Madison