1. Department of Microbiology, Immunology and Molecular Genetics, University of Kentucky, Lexington, KY 40536, USA.
2. Sanders Brown Center on Aging, University of Kentucky, Lexington, KY 40536, USA.
3. Department of Neurology, University of Kentucky, Lexington, KY 40536, USA.
4. Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, CO 80523, USA.
5. Colorado Division of Wildlife, Wildlife Research Center, Fort Collins, CO 80526, USA.