Forest fragmentation predicts local scale heterogeneity of Lyme disease risk
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.
- Falco RC, Fish D (1988) Prevalence of Ixodes scapularis near the homes of Lyme disease patients in Westchester County, New York. Am J Epidemiol 126:826–830Google Scholar
- Hurd JD, Civco DL (1996) Land use and land cover mapping for the state of Connecticut and portions of New York state in the Long Island Sound Watershed. In: Presented at the GIS/LIS’96 Convention, Denver, CO, pp 564–572Google Scholar
- Leopold A (1933) Game management. Charles Scribner’s Sons, New YorkGoogle Scholar
- Levine N (2000) CrimeStat, 1.1 edn. Ned Levine and Associates, AnnandaleGoogle Scholar
- McGarigal K, Marks BJ (1995) FRAGSTATS: spatial pattern analysis for quantifying landscape structure. In: US Department of Agriculture, Forest Service, Pacific Northwest Research Station, Portland, OregonGoogle Scholar
- Orloski KA, Hayes EB, Campbell GL, Dennis DT (2000) Surveillance for Lyme disease–United States, 1992–1998. Morbidity and Mortality Weekly Report 49:1–11Google Scholar
- Thompson SK (1992) Sampling. Wiley, New YorkGoogle Scholar
- Turner MG, H GR, O’Neill RV (2001) Landscape ecology in theory and practice. Springer, Berlin Heidelberg New YorkGoogle Scholar
- US Census Bureau (2000) Redistricting Census 2000 TIGER/Line Files [machine-readable data files]. In, WashingtonGoogle Scholar
- Wilson ML, Adler GH, Spielman A (1985) Correlation between deer abundance and that of the deer tick Ixodes dammini (Acari: Ixodidae). Ann Entomol Soc Am 78:172–176Google Scholar