Geographic risk for lyme disease and human granulocytic ehrlichiosis in southern New York state - PubMed (original) (raw)

Geographic risk for lyme disease and human granulocytic ehrlichiosis in southern New York state

T J Daniels et al. Appl Environ Microbiol. 1998 Dec.

Abstract

Ixodes scapularis, the tick vector of Lyme disease and human granulocytic ehrlichiosis (HGE), is prevalent in much of southern New York state. The distribution of this species has increased, as have reported cases of both Lyme disease and HGE. The unreliability of case reports, however, demonstrates the need for tick and pathogen surveillance in order to accurately define areas of high risk. In this study, a total of 89,550 m2 at 34 study sites was drag sampled in 1995 and a total of 51,540 m2 at 40 sites was sampled in 1996 to determine tick and pathogen distribution in southern New York state. I. scapularis was collected from 90% of the sites sampled, and regionally, a 2.5-fold increase in nymphal abundance occurred from 1995 to 1996. I. scapularis individuals from all sites were infected with Borrelia burgdorferi in 1995, while an examination of ticks for both B. burgdorferi and the agent of HGE in 1996 confirmed that these organisms were present in all counties; the average coinfection rate was 1.9%. No correlation was found between estimated risk and reported cases of Lyme disease. The geographic disparity of risk observed among sites in this study underscores the need for vector and pathogen surveillance on a regional level. An entomologic risk index can help identify sites for targeted tick control efforts.

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Figures

FIG. 1

FIG. 1

Map of study sites sampled in the lower Hudson Valley, New York, in 1995 and 1996. Asterisks indicate sites that were sampled only in 1995, and plus signs indicate sites that were sampled only in 1996.

FIG. 2

FIG. 2

Comparison of woodland nymphal I. scapularis densities at sites in the lower Hudson Valley in 1995 and 1996. The means were adjusted for seasonal variation. The location of the Hudson River relative to the counties is shown. Rockland and Westchester counties are the southernmost counties; Ulster and Dutchess counties are the northernmost counties.

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