A HEADACHE FROM OUR PAST? INTRACRANIAL ABSCESS DISEASE, VIRULENCE FACTORS OF TRUEPERELLA PYOGENES, AND A LEGACY OF TRANSLOCATING WHITE-TAILED DEER ( ODOCOILEUS VIRGINIANUS).

Trueperella pyogenes, a bacterial opportunistic pathogen residing along the skin layer of apparently healthy animals, is the etiologic agent of intracranial abscessation-suppurative meningoencephalitis, a cause of mortality for male white-tailed deer ( Odocoileus virginianus). Occurrence of this disease has been speculated to be influenced by virulence of T. pyogenes residing on white-tailed deer in geographically distinct metapopulations. To determine if differences in virulence potential of T. pyogenes could affect occurrence of disease across populations, we examined if frequency of seven virulence genes of T. pyogenes from forehead swabs of 186 apparently healthy white-tailed deer differed between sites in the state of Georgia, US, where ≥1 male tested positive for a cranial abscess and sites where no individuals tested positive for a cranial abscess. We detected six of seven virulence genes more frequently at sites where we detected ≥1 male with a cranial abscess compared to sites where we did not detect any individuals with a cranial abscess ( nanH, P<0.001; nanP, P=0.007; fimA, P<0.001; fimC, P=0.037; fimE, P<0.009; fimG, P<0.001; and cbpA, P=0.872). Our findings suggest differences in the pathogenic potential of T. pyogenes at individual sites may help to explain spatial variability of this disease. Anecdotally, the incidence of cranial abscess disease in Georgia seems to be associated with areas that were restocked with white-tailed deer from a high-fenced property in Wisconsin, US. Given the spatial distribution of this disease, we speculate that 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.

EPIZOOTIOLOGY OF CRANIAL ABSCESS DISEASE IN WHITE-TAILED DEER (ODOCOILEUS VIRGINIANUS) OF GEORGIA, USA.

Intracranial abscess disease is a cause of natural mortality for mature male white-tailed deer (Odocoileus virginianus). Most cases of abscesses are associated with bacterial infection by Trueperella (Arcanobacterium) pyogenes, but a complete understanding of the epidemiology of this disease is lacking. We quantified the effects of individual characteristics, site-specific herd demographics, land cover, and soil variables in estimating the probability of this disease. We examined 7,545 white-tailed deer from 60 sites throughout Georgia US for signs of cranial abscesses, the predecessor of intracranial abscesses, and recorded the presence or absence of cranial abscesses for each individual examined. We detected no cranial abscesses in 2,562 female deer but 91 abscesses in 4,983 male deer examined (1.8%). A generalized linear mixed model, treating site as a random effect, was used to examine several potential explanatory risk factors including site-level landscape and soil characteristics (soil and forest type), demographic factors (deer density and male to female ratio), and individual host factors (deer sex and age). Model results indicated that the probability of a male having a cranial abscess increased with age and that adult sex ratio (male:female) was positively associated with this disease. Site-specific variables for land cover and soil types were not strongly associated with observations of the disease at the scale measured and a large amount of among-site variability remained. Given the demonstrated effect of age, gender, and local sex ratios but the remaining unexplained spatial variability, additional investigation into spatiotemporal variation of the presumed bacterial causative agent of cranial abscesses appears warranted.

Isolation and genotypic characterization of Trueperella (Arcanobacterium) pyogenes recovered from active cranial abscess infections of male white-tailed deer (Odocoileus virginianus).

Trueperella (Arcanobacterium) pyogenes is a causative agent of suppurative infections in domestic and wild animals. In some populations of captive or free-ranging white-tailed deer (Odocoileus virginianus), cranial abscess disease is an important source of mortality in adult males. Although the pathogenesis of this disease is poorly understood, T. pyogenes has been isolated from active infections with other opportunistic bacteria. In this study, bacteria associated with cranial abscess infections were identified, the prevalence of T. pyogenes associated with these infections was determined, and the presence of known virulence determinants in T. pyogenes isolates was ascertained. Using routine biochemical techniques seven bacterial species were identified from 65 samples taken from active cranial abscess infections of 65 male white-tailed deer. Trueperellapyogenes was recovered from 46 samples; in 32 samples it was the only bacterium species detected. Staphylococcus aureus was detected in 26 samples. From these samples, the presence of known and putative virulence genes of T. pyogenes--plo, nanH, nanP, cbpA, fimA, fimC, fimE, and fimG--was examined by conventional polymerase chain reaction. All T. pyogenes isolates were positive for the pyolysin genes plo, nanP, and fimA. Furthermore, nanH, fimA, fimC, and fimE were detected in over 70% of isolates. Of the isolates tested, 48% had genotypes containing all virulence genes except cbpA. The suggestive virulence potential of all isolates, coupled with the large number of pure cultures obtained, implies that T. pyogenes is a causative agent of cranial abscess disease.

Epethelial presence of Trueperella pyogenes predicts site-level presence of cranial abscess disease in white-tailed deer (Odocoileus virginianus).

Cranial/intracranial abscess disease is an emerging source of significant mortality for male white-tailed deer (Odocoileus virginianus). Most cases of cranial/intracranial abscess disease are associated with infection by the opportunistic pathogen Trueperella pyogenes although the relationship between the prevalence of the bacteria and occurrence of disease is speculative. We examined 5,612 hunter-harvested deer from 29 sites across all physiographic provinces in Georgia for evidence of cranial abscess disease and sampled the forehead, lingual, and nasal surfaces from 692 deer. We used polymerase chain reaction (PCR) to determine presence of T. pyogenes from these samples. We found T. pyogenes prevalence at a site was a predictor for the occurrence of cranial abscess disease. Prevalence of T. pyogenes did not differ between samples from the nose or tongue although prevalence along the forehead was greater for males than females (p = 0.04), particularly at sites with high occurrence of this disease. Socio-sexual behaviors, bacterial prevalence, or physiological characteristics may predispose male deer to intracranial/cranial abscess disease. Determination of factors that affect T. pyogenes prevalence among sites may help explain the occurrence of this disease among populations.