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

James H. Oliver, Jr.

Committee Member 1

Lance A. Durden

Committee Member 2

Daniel V. Hagan

Abstract

The abilities of the southeastern tick Ixodes minor Neumann and the eastern tick Ixodes scapularis Say (blacklegged tick) from the U.S., to acquire, maintain, and transmit a northeastern strain of Borrelia burgdorferi sensu stricto Johnson, Schmid, Hyde, Steigerwalt & Brenner (B.b.s.s.) were compared under laboratory conditions. Also, the infectivities via needle injection, of several southeastern Borrelia burgdorferi sensu lato (B.b.sA.) isolates in rodents were examined. Ixodes minor larvae were fed on isolate SH2- 82 (B.b.s.s) infected Mesocricetus auratus (Waterhouse) (Syrian hamsters) and subsequently examined via tick culture in Barbour-Stoenner-Kelley (BSK-H) medium for infection. The remaining larvae were allowed to ecdyse and then were fed on uninfected Sigmodon hispidus Say & Ord (cotton rats) and Mus musculus L. (laboratory mice). Fed nymphs were tested for infection via tick culture and their host rodents were tested for infection via ear clip tissue in BSK-H medium culture. Ixodes scapularis larvae were then ted on the same SH2-82 infected hamsters one week after I. minor larvae had fed and dropped from the hamsters. The engorged larvae were allowed to ecdyse to nymphs and then were fed on uninfected laboratory mice. Fed nymphs were tested for infection with B. burgdorferi s.s. via tick culture in BSK-H medium and host animals were tested via ear clip tissue samples in culture. Ixodes minor larvae were able to acquire spirochetes (66%, n = 50) but only maintained an infection rate of 26% (n = 90) transstadially into the nymphal stage. Ixodes scapularis maintained an infection rate of 76% (n = 41) transstadially from larvae to nymphs. Moreover, I. scapularis transmitted the SH2-82 strain of B. burgdorferi s.s. to 100% (n = 5) of the uninfected mice on which it fed, whereas I. minor nymphs failed to transmit this spirochete to uninfected cotton rats (n = 5) or laboratory mice (n = 5).

Isolates of B. burgdorferi sensu lato from three southeastern U.S. states (Florida, Georgia, and South Carolina) were grown in BSK-H culture medium and injected into laboratory rodents. The infectivity of the following isolates were examined: AI-1 (B. bissettii subgroup), MI-5 (B. burgdorferi s.s.), MI-8 (new genospecies), SCCH-2 (B. burgdorferi s.s.), SCI-4 (B. burgdorfen s.s.), SI-10 (B. andersonii), and SM-1 (B. burgdorferi s.s.). All rodents were tested four weeks post-injection via ear clip tissue culture for infection with B. burgdorferi sensu lato. SCCH-2 was the only isolate which infected 100% of rodents (n = 5). Isolates SCI-4 (n = 5) and SM-1 (n=5) both infected 60% of rodents. Isolates AI-1 (n = 14), MI-5 (n = 5), MI-8 (n = 19), and SI-10 (n = 5) failed to infect rodents via needle injection.

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