1. James L. Voss Veterinary Teaching Hospital, Colorado State University, College of Veterinary Medicine and Biomedical Sciences, 300 West Drake Road, Fort Collins, Colorado 80523, USA
2. Infectious Diseases Laboratory, University of Georgia, 110 Riverbend Rd, Athens, Georgia 30602, USA
3. Department of Clinical Sciences, Colorado State University, College of Veterinary Medicine and Biomedical Sciences, 300 West Drake Road, Fort Collins, Colorado 80523, USA