9th International Deer Biology Congress

AUTHORS: Bradley S. Cohen, Daniel B. Warnell School of Forestry and Natural Resources, University of Georgia; Emily H. Belser, Daniel B. Warnell School of Forestry and Natural Resources, University of Georgia, and Caesar Kleburg Wildlife Research Institute, Texas A&M University–Kingsville; Shamus P. Keeler, Southeastern Cooperative Wildlife Disease Study, College of Veterinary Medicine, University of Georgia; Michael J. Yabsley, Daniel B. Warnell School of Forestry and Natural Resources, University of Georgia, and Southeastern Cooperative Wildlife Disease Study, College of Veterinary Medicine, University of Georgia; Karl V. Miller, Daniel B. Warnell School of Forestry and Natural Resources, University of Georgia

ABSTRACT: Intracranial abscessation-suppurative meningoencephalitis, commonly referred to as a brain abscess, is a reported cause of natural mortality, particularly for mature, male white-tailed deer (Odocoileus virginianus). Most cases of brain abscesses are associated with infection by the opportunistic bacterium Trueperella pyogenes (formerly Arcanobacterium pyogenes) but little else is known about the disease. We examined 4983 male white-tailed deer across 60 sites throughout Georgia, USA for signs of cranial abscesses, the etiological predecessor of brain abscesses, to model the distribution of the disease across the state and investigate risk factors for the disease. A generalized linear mixed model treating property as a random effect suggested that age was the most important risk factor. Furthermore, vegetation and soil features of each site were not strongly associated with increasing risk of the disease. However, the model suggested that a large amount of variance occurred at the site level.

We speculated the occurrence of this disease to be influenced by virulence of T. pyogenes residing along the skin layer of white-tailed deer in geographically distinct metapopulations. To investigate if the virulence of T. pyogenes was affecting the variation in disease occurrence across sites, we examined the infectious potential of T. pyogenes from the foreheads of apparently healthy male white-tailed deer harvested from a subsample of 28 of 60 sites (Fig. 1). We used Polymerase Chain Reaction (PCR) to determine the presence of seven different virulent determinants. Six of the seven virulence determinants, all of which promote bacterial adhesion to epithelium, were more commonly detected on properties where abscesses were found (p≤0.05; Fig. 2). Our findings suggest differences in pathogenic-potential of T. pyogenes at individual sites may help explain spatial variability of this disease. Incidence of cranial abscess disease in Georgia appears associated with areas restocked with white-tailed deer from a single location in Wisconsin between 1962 and 1963 (Fig.1). Given the spatial distribution of this disease, we speculate these genetic differences in T. pyogenes may have arisen from white-tailed deer restocking efforts, and our observations may be a legacy of an introduced disease manifesting itself generations later.