Term of Award

Spring 2001

Degree Name

Master of Science

Document Type and Release Option

Thesis (restricted to Georgia Southern)

Department

Department of Biology

Committee Chair

Lance A. Durden

Committee Member 1

Quentin Q. Fang

Committee Member 2

James H. Oliver, Jr.

Abstract

Human granulocytic ehrlichiosis (HGE) is a newly emerging, tick-borne zoonosis in North America. The agent that causes HGE is very similar to Ehrlichia phagocytophilia and Ehrlichia equi, but has yet to be classified as a separate species.

This study was carried out in order to determine the prevalence rate of HGE infection in blacklegged ticks (Ixodes scapularis) in insular and mainland sites in southeastern Georgia using nested PCR techniques. Four locations were studied representing 2 barrier islands and 2 mainland sites. We hypothesized that areas that have low levels of human disturbance and are somewhat isolated will have a higher prevalence of infected ticks than areas where there is more disturbance and no geographical barriers. Ticks were collected from each of the four sites and DNA was extracted from them in the laboratory. The DNA was amplified using a nested PCR assay and then visualized on a 1% agarose gel. All positive samples were re-tested in order to confirm that there were no false positives. Selected products were then sequenced Our hypothesis was supported by the results, which showed the island populations of ticks to have similar prevalence rates, but when compared to the mainland sites, there was a significant difference in prevalence. On Sapelo Island, 25 of 151 (16.6%) ticks were positive, and on Jekyll Island, 6 of 382 (1.6%) ticks were positive On both mainland sites, there were no positive ticks screened. In Bulloch County, 112 ticks were sampled and 0 were positive (0.0%), and in Emanuel County, 18 ticks were screened and 0 were positive (0.0%) for the HGE agent. Human disturbance or the availability of competent reservoir hosts may play an important role in these results, as well as low levels of bacteremia in the reservoir ticks.

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