Cooperative Fish and Wildlife Research Units Program: Pennsylvania
Education, Research and Technical Assistance for Managing Our Natural Resources

Chronic wasting disease (CWD) is a transmissible spongiform encephalopathy that was first detected in 1967 in a captive research facility in Colorado. In the northeastern United States (Northeast), CWD was first confirmed in 2005 in New York and West Virginia, and has since been found in Maryland, Virginia, and Pennsylvania. Because CWD is a new and emerging disease in populations of white-tailed deer (Odocoileus virginianus) in the central Appalachian region and has yet to be assessed within a Bayesian hierarchical modeling framework, we examined demographic and environmental factors to better understand the spatial epidemiology of CWD in the region. The objectives of our study were to (1) apply Bayesian hierarchical models to harvest location data of white-tailed deer tested for CWD in the central Appalachian region between 2005 and 2012, (2) identify covariates that best described the spatial distribution of CWD, and (3) predict probability of risk for CWD infection in the Northeast. Demographic covariates included sex and age, and environmental covariates included elevation, slope, riparian corridor, percent of clay-sized particles in the soil, and percent of three habitat types (developed, forested, and open). For each deer, environmental covariates were extracted within 6 km2 grid cells as this size reflected estimates of 99% isopleths for home range of white-tailed deer in the region. The model with the most support contained random spatial effects and percent habitat and accounted for 94.4% of the overall weight for the candidate set of hierarchical models. Percent forest cover had the strongest relationship with the distribution of CWD in the region, with increased risk of CWD occurring in areas that had lower amounts of forest cover. Our results will assist resource managers in understanding the spatial distribution of CWD not only within the study area, but also in surrounding areas where CWD has yet to be found. Efficiency of disease surveillance and containment efforts can be improved by allocating resources used for surveillance into areas that are at a greater risk for infection.