I>Borrelia burgdorferi Not Detected in Widespread Ixodes scapularis (Acari: Ixodidae) Collected From White-Tailed Deer in Tennessee

Center for Wildlife Health, University of Tennessee Institute of Agriculture, Knoxville, 37996, USA.
Journal of Medical Entomology (Impact Factor: 1.95). 11/2012; 49(6):1473-80. DOI: 10.1603/ME11255
Source: PubMed


Lyme disease (LD), caused by the bacterium Borrelia burgdorferi and transmitted in the eastern United States by blacklegged ticks, Ixodes scapularis Say, is classified as nonendemic in Tennessee and surrounding states in the Southeast. Low incidence of LD in these states has been attributed, in part, to vector ticks being scarce or absent; however, tick survey data for many counties are incomplete or out of date. To improve our knowledge of the distribution, abundance, and Borrelia spp. prevalence of I. scapularis, we collected ticks from 1,018 hunter-harvested white-tailed deer (Odocoileus virginianus (Zimmerman)) from 71 of 95 Tennessee counties in fall 2007 and 2008. In total, 160 deer (15.7%) from 35 counties were infested with adult I. scapularis; 30 of these counties were new distributional records for this tick. The mean number of I. scapularis collected per infested deer was 5.4 +/- 0.6 SE. Of the 883 I. scapularis we removed from deer, none were positive for B. burgdorferi and one tested positive for B. miyamotoi. Deer are not reservoir hosts for B. burgdorferi; nevertheless, past surveys in northern LD-endemic states have readily detected B. burgdoreferi in ticks collected from deer. We conclude that I. scapularis is far more widespread in Tennessee than previously reported. The absence of detectable B. burgdorferi infection among these ticks suggests that the LD risk posed by I. scapularis in the surveyed areas of Tennessee is much lower than in LD-endemic areas of the Northeast and upper Midwest.

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Available from: Graham J. Hickling, Dec 13, 2014
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    • "In the forests of eastern North America the white-footed mouse, Peromyscus leucopus, is its main reservoir [25,26]. On the other hand, white-tailed deer (Odocoileus virginianus, WTD) are the primary reproductive host for I. scapularis in the US, but they are reservoir-incompetent for B. burgdorferi[19,27]. A number of studies have suggested that vertebrate species diversity affects the risk of contracting human LD [28-32]. "
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    ABSTRACT: Disease risk maps are important tools that help ascertain the likelihood of exposure to specific infectious agents. Understanding how climate change may affect the suitability of habitats for ticks will improve the accuracy of risk maps of tick-borne pathogen transmission in humans and domestic animal populations. Lyme disease (LD) is the most prevalent arthropod borne disease in the US and Europe. The bacterium Borrelia burgdorferi causes LD and it is transmitted to humans and other mammalian hosts through the bite of infected Ixodes ticks. LD risk maps in the transboundary region between the U.S. and Mexico are lacking. Moreover, none of the published studies that evaluated the effect of climate change in the spatial and temporal distribution of I. scapularis have focused on this region. The area of study included Texas and a portion of northeast Mexico. This area is referred herein as the Texas-Mexico transboundary region. Tick samples were obtained from various vertebrate hosts in the region under study. Ticks identified as I. scapularis were processed to obtain DNA and to determine if they were infected with B. burgdorferi using PCR. A maximum entropy approach (MAXENT) was used to forecast the present and future (2050) distribution of B. burgdorferi-infected I. scapularis in the Texas-Mexico transboundary region by correlating geographic data with climatic variables. Of the 1235 tick samples collected, 109 were identified as I. scapularis. Infection with B. burgdorferi was detected in 45% of the I. scapularis ticks collected. The model presented here indicates a wide distribution for I. scapularis, with higher probability of occurrence along the Gulf of Mexico coast. Results of the modeling approach applied predict that habitat suitable for the distribution of I. scapularis in the Texas-Mexico transboundary region will remain relatively stable until 2050. The Texas-Mexico transboundary region appears to be part of a continuum in the pathogenic landscape of LD. Forecasting based on climate trends provides a tool to adapt strategies in the near future to mitigate the impact of LD related to its distribution and risk for transmission to human populations in the Mexico-US transboundary region.
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