1. Livestock Medicine and Surgery Service, Department of Clinical Sciences, College of Veterinary Medicine and Biological Sciences, Colorado State University, Fort Collins, CO
2. Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California-Davis, Davis, CA
3. Department of Microbiology, Immunology, and Pathology, College of Veterinary Medicine and Biological Sciences, Colorado State University, Fort Collins, CO