Term of Award
Master of Science in Biology
Document Type and Release Option
Thesis (restricted to Georgia Southern)
Department of Biology
James H. Oliver, Jr.
Committee Member 1
Lance A. Durden
Committee Member 2
David C. Rostal
Reservoir competence of the broad-headed skink, Eameces laticeps, for Borrelia burgdorferi was evaluated. Attempts to infect broad-headed skinks with MI-2 strain spirochetes were unsuccessful. Spirochetes could not be isolated from various tissues of seven lizards at least 30 days after they had been inoculated with 107 spirochetes. Also, none of the xenodiagnostic tick larvae (n = 70) acquired spirochetes from any of the needle-inoculated skinks. Similarly, spirochetes could not be detected in the tissues from each of the three lizards that were fed upon by 1 1 putativcly infected Ixodes scapularis nymphs. In contrast, seven of eight (88%) needle-inoculated mice were successfully infected with MI-2 strain spirochetes. Furthermore, nymphs that resulted from larval feedings on culture positive mice successfully transmitted B. burgdorferi to 76% of the mice that they were allowed to feed on.
The underlying factor for our inability to isolate B. burgdotferi from E. laticeps was the presence of a borreliacidal factor in the lizard plasma. Twenty-two adult ticks that resulted from putatively infected nymphs that had fed on broad-headed skinks were culture negative, suggesting that the spirochetes were eliminated from their midguts. Borreliacidal activity of plasma from E. laticeps was demonstrated in the laboratory whereas there was no such effect in plasma from reservoir-competent laboratory mice. Virtually all spirochetes placed in plasma derived from four lizards died within 13 hours post-inoculation. In contrast, more than 89% of spirochetes survived in the plasma from two mice. The borreliacidal factor appears to be heat labile; more than 79% of the spirochetes survived in preheated skink plasma. These results suggest that E. laticeps is a reservoir incompetent host for B. burgdorferi.
Transmission of MI-2 strain B. burgdorferi via cofeeding on Borrelia-incompetent hosts (E. laticeps and guinea pigs) was investigated. Infected nymphs and uninfected larvae were allowed to feed together on two broad-headed skinks or three tick naive guinea pigs. Larval ticks were added for approximately 13 days and detached resulting nymphs were evaluated for the presence of spirochetes in BSK II culture 15 days after ecdysis. Also, a portion of resulting nymphs that cofed as larvae with infected nymphs on a guinea pig was used in an attempt to transmit spirochetes to uninfected mice. Overall, none of the cultured nymphs tested positive for spirochetes, and the resulting nymphs that were not cultured, but instead fed on mice, failed to transmit B. burgdorferi to the mice. These results indicate that transmission of B. burgdorferi did not occur between infected ticks and non-infected ones cofeeding on Borrelia-incompetent hosts.
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Murrell, Brian Patrick, "Studies of Susceptibility of Broad-Headed Skinks (Eumeces laticeps) and Laboratory Mice (Mus musculus) to Strain MI-2 of Borrelia burgdorferi and Vector Competence of the Tick Ixodes scapularis" (2002). Legacy ETDs. 284.