The distribution of canine exposure to Borrelia burgdorferi in a Lyme- disease endemic area

Objectives. A serosurvey of canine exposure to Borrelia burgdorferi, the causative agent of human Lyme disease, was conducted in Westchester County, New York, to determine the distribution of exposure in an area endemic for Lyme disease. Methods. A total of 1446 blood samples was collected from resident dogs and tested by modified enzyme-linked immunosorbent assay. Equivocal samples were further tested by immunoblot. A mean number of 57.8 samples was collected from each of 25 towns and cities. Results. Seroprevalence rates for municipalities ranged from 6.5% to 85.2%. County seroprevalence was 49.2%. There was a significant difference among the rates for the northern (67.3%), central (45.2%), and southern (17.3%) regions. Multiple range analysis indicated homogeneity between the southern and central regions and the central and northern regions. Conclusions. Canine exposure to B burgdorferi increases in a south to north gradient within the county. Intensity of exposure, measured by enzyme-linked immunosorbent assay titers, indicates a similar pattern. The close association between dogs and humans suggests that human risk of acquiring Lyme disease within Westchester County is equally disparate and is inversely related to the degree of urbanization.