Combining health and population data collected in 2006 from 54 Brazilian health districts in a corner of the Brazilian Amazon near the border with Peru with high-resolution satellite data showing changes in land cover, the scientists showed that relatively small alterations to the forest can have large implications for human health. ‘A four per cent change in forest cover was associated with a 48 per cent increase in malaria incidence in these 54 health districts,’ said Sarah Olson, the lead author of the report in the online journal Emerging Infectious Diseases.

The clearing of forest creates conditions that favour malaria’s primary vector in the Amazon, the mosquito Anopheles darlingi. ‘The deforested landscape, with more open spaces and partially sunlit pools of water, appears to provide ideal habitat for this mosquito,’ Olson said. Indeed, under such conditions, A. darlingi has been shown to displace other mosquito species that prefer forest and are less likely to transmit malaria.

The new study complements previous work the team carriedout that showed that in the Peruvian Amazon, abundance of the mosquito’s larvae was correlated with aquatic breeding sites in disturbed habitats following land clearance.

Malaria infected an estimated 500,000 Brazilians annually across the Amazon Basin between 1997 and 2006.

August 2010