Link Between Malaria Epidemics and Rainforest Destruction in the Peruvian Amazon

A new study, to be published by the American Journal of Tropical Medicine and Hygiene in January 2006, is the first to demonstrate a link between deforestation and epidemic malaria in the Amazon rainforest. Not only does this work have critical implications for global malaria control, there are immediate policy implications for governmental ministries who need to understand that there is a direct link between uncontrolled, government-sponsored and encouraged rainforest and ecological degradation, disease epidemics and emergence, and systemic economic harm in both the short- and long-term.

Amy Vittor, a Johns Hopkins graduate student and currently a medical student at Stanford University, under the supervision of Jonathan Patz, now at the University of Wisconsin, and other collaborators, carried out a field study in the Amazon region in northeastern Peru to examine the question whether the epidemic reappearance of malaria in the Peruvian Amazon in the 1990s was related to destruction of rainforest.

Over one year, the investigators collected mosquitoes at sites with varying amounts of deforestation and other anthropogenically-driven changes along a newly constructed road. The authors found that the abundance of a particularly dangerous mosquito, Anopheles darlingi, was over 200-fold higher in deforested locations compared to more pristine rainforest sites: a relationship that held up even after considering human population density. This mosquito species is the major vector of malaria in the Amazon basin and is particularly dangerous since, similar to its cousin in sub-Saharan Africa An. gambiae, An. darlingi is highly attracted to people. These results indicate that this major mosquito vector of malaria in the Amazon is significantly affected by habitat and land cover change due to deforestation.

Anopheles darlingi had not existed in western Amazonia as of the late 1980s, and had only moved westward across the Amazon basic from Brazil since that time. Rapid development, accompanied by deforestation brought humans into increased contact with a variety of emerging infectious diseases in the region including yellow fever, leishmaniasis, and leptospirosis, with the constant potential for new, previously unidentified diseases emerging such as mosquito and rodent borne hemorrhagic fevers. Man’s alteration of local landscape may now explain the parallel rapid rise of malaria cases in the Amazon region.

According to the senior author of this paper, Patz, accompanying analyses on mosquito-larval habitat and human epidemiology are forthcoming; he says that preliminary results confirm this link between deforestation and malaria risk in the Amazon.

In an accompanying editorial, Burton Singer, Robertson Professor of Public and International Affairs at Princeton University and Marcia Caldas de Castro of the University of South Carolina at Columbia, note that “Malaria in the Amazon over the past 100+ years has been driven by eco-system transformations consequential to human migration and the opening of frontier lands for agricultural settlement, cattle ranching, and natural resource extraction. Deforestation, and even some limited reforestation, has been an omnipresent part of this process. However, the linkage between deforestation, as such, and malaria transmission is a subtle process requiring analysis at several temporal and spatial scales.”

Singer and Caldas de Castro also point out that “government sponsored colonization projects and substantial informal migration, all accompanied by deforestation, have resulted in considerable malaria outbreaks. They conclude that “contemporary Peruvian and Brazilian Amazon situations of frontier expansion, heavy deforestation, and accompanying outbreaks of malaria transmission would seem to make a strong case for sharply curtailing this process and, simultaneously, preserving an invaluable eco-system. However, as clearly indicated by current frontier expansion in the Brazilian state of Amazonas, the practical issue regarding malaria is one of providing effective mitigation strategies, linked to broad-gauged monitoring and surveillance. Here, fine-grained entomological and community assessments can provide ground-truth for risk assessment using satellite imagery that captures the ongoing transformation of forest fringe, partial shade areas, and sites of standing water.”

Other contributors to the paper were Robert H. Gilman, James M. Tielsch, Gregory E. Glass, Timothy M. Schields of the Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland; and Wagner Sanchez Lozano and Viviana Pinedo Cancino of Asociación Benéfica PRISMA, Lima, Peru.

Contacts:

Dr. Jonathan Patz, senior author of the paper, may be contacted at the Center for Sustainability and the Global Environment, Nelson Institute for Environmental Studies, University of Wisconsin, Madison. Tel. 608.262.4775; Fax 608.265.4113; [email protected]

Dr. Joseph M. Vinetz, Associate Editor, American Journal of Tropical Medicine and Hygiene, may be contacted at Tel. 858.822.4469 or [email protected]

Dr. James Kazura, Editor-in-Chief, American Journal of Tropical Medicine and Hygiene may be contacted at Tel. 216.368.6940 or [email protected]

Cathi Siegel, Managing Editor, American Journal of Tropical Medicine and Hygiene may be contacted at 216.368.6940 or [email protected]

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