Forest fragmentation predicts local scale heterogeneity of Lyme disease risk
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Fragmentation of the landscape has been proposed to play an important role in defining local scale heterogeneity in Lyme disease risk through influence on mammalian host density and species composition. We tested this observed relationship in a suburban region around Lyme, Connecticut, where we collected data on the density of the tick vector, Ixodes scapularis and prevalence of the Lyme bacterium, Borrelia burgdorferi at 30 sites. Analysis of the landscape pattern of forest patches was performed using satellite imagery. The calculated landscape indices, which included patch size and isolation, revealed a positive link between fragmentation and both tick density and infection prevalence in ticks. In spite of higher entomologic risk, human incidence of Lyme disease is lower in fragmented contexts suggesting that entomologic risk is not the critical driver of human infections. These results represent a departure from the prior claims that fragmentation and human Lyme disease risk are positively linked. A complete understanding of the influence of landscape fragmentation will allow for improved risk mapping and potential environmental management of Lyme disease.
KeywordsDisease vectors Geographic information systems Ixodes Landscape epidemiology Ticks
The authors thank Nita Madhav and Susan Van Ness for their assistance. J.S. Brownstein was supported by NASA Headquarters under the Earth Science Fellowship Grant NGT5-01-0000-0205 and the National Science and Engineering Research Council of Canada. This work was also supported by The G. Harold and Leila Y. Mathers Charitable Foundation (DF) and a USDA-ARS Cooperative Agreement 58-0790-2-072 (DF). The experiments described here comply with the current laws of the United States.
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