Graham Environmental Sustainability Institute

Vector-Transmitted Diseases in a Changing World

Principal Investigators: Mercedes Pascual, Ed Ionides, and Ivette Perfecto.

Units Involved: College of Engineering, College of Literature, Arts, & Sciences, and School of Natural Resources & Environment.

Brief Project Description: The proposed research seeks to explore the relationship between sustainability and vector transmitted diseases of humans in the current landscape mosaic of the tropical world. The two chosen diseases, malaria and cutaneous leishmaniasis, are arguably among the most important emerging and resurging vector-borne diseases, in terms of the number of affected people in different continents. The prevalence of these and other vector borne pathogens are on the rise around the tropics, they produce high human morbidity and mortality, particularly in areas where these pathogens are emerging; areas of the world where ‘innate’ host resistance is low. There is increased recognition that multiple environmental trends are at play, and can even interact with each other, to drive observed disease patterns, including changes in land-use and climate. There is therefore a pressing need to understand and define our ability to forecast the seasonal and interannual dynamics of disease in the context of human-induced environmental change at longer temporal scales.

This proposal seeks to expand our current work on infectious diseases and environmental variability to focus on vector-transmitted diseases and address their dynamics in the context of environmental change. We seek to specifically understand; (1) how the fast dynamics (annual outbreaks and multiyear cycles) of malaria in transition regions, where incidence has increased in the past decades and epidemic behavior is now evident, have responded to patterns of human-induced change; (2) how land-use changes related to agricultural practices have influenced the temporal dynamics and spatial distribution of malaria and cutaneous leishmaniasis; and (3) whether and how land-use change has modified the association of these diseases with climate variability (ENSO, rainfall and temperature) and therefore, the feasibility and accuracy of early-warning systems. Proposed case studies include malaria in semi-arid regions of India experiencing dramatic change in irrigation patterns, and cutaneous leishmaniasis in Costa Rica where increased deforestation has led to the fragmentation of vast landscapes that were formerly continuous rain forests.

The general dynamics underlying massive change in land-use patterns in the tropics include the continuing trend of intensification of agriculture, which leads to a continuing destruction of natural habitats, the continued concentration of land-holdings, the associated increases in the number of landless poor in rural areas and the massive movement of people away from rural areas. The resulting pattern in the developing word is one in which there are fragments of natural habitat in a sea of intensive agriculture, dotted with urban areas which are themselves increasingly dominated by peri-urban slums. Exploring the general consequences of this pattern is arguably the central question of sustainability and the conservation of biodiversity. Despite the tremendous advances of theory and models in infectious disease dynamics, the full role of disease ecology has not been the focus of quantitative study. This proposal will take initial important steps in this direction.

Significant Accomplishments (as of January 1, 2009)

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