Environmental Determinants of Lyme Disease Foci

Project institution: College of Veterinary Medicine, University of Illinois

Principal investigator: Dr. Uriel Kitron

The distribution of Ixodes scapularis (dammini) and Borrelia burgdorferi in the north-central United States consists of an extensive endemic area in west-central Wisconsin and eastern Minnesota, with smaller disparate enzootic foci to the south, north and east, ranging from northern Wisconsin and the Upper Peninsula of Michigan to northern Illinois and Indiana.

Vegetation, soil, and the size of suitable habitat patches appear to be limiting the establishment of the tick away from the center of its distribution. Although sandy soils and hardwood or mixed forests (such as the sandy oak pine barrens of west central Wisconsin) provide preferred tick habitat, ticks are also found in finer soils and pine forests within the heart of the tick distribution in the region.

Mapping the distribution of ticks found on white-tailed deer suggests that tick distribution may be expanding, particularly eastward in Wisconsin, and that new and isolated foci are appearing at the extremes of known tick distribution. A GIS is being used to overlay the distribution of infested deer with other layers in an environmental database to precisely identify the probable foci. Canine serology is also being used to further map the distribution of Lyme disease Borrelia in the region, using address-level data from participating veterinary clinics.

To identify the environmental determinants of tick distribution, Landsat Thematic Mapper data for the whole region are being integrated with other landcover/landuse databases and with field-collected vegetation and soil data. These data are also being used to determine tick habitat profiles and the degree of association between diferent landscape variables and tick density.

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Last updated: 6 May 1999