1 Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Washington State University, Pullman, WA 99164.
| 2 Present address is Marion duPont Scott Equine Medical Center, Virginia-Maryland Regional College of Veterinary Medicine, Virginia Tech, Leesburg, VA 20177.
| 3 Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Washington State University, Pullman, WA 99164.
| 4 Departments of Veterinary Microbiology and Pathology, College of Veterinary Medicine, Washington Animal Disease Diagnostic Laboratory, Pullman, WA 99164.
| 5 Washington Animal Disease Diagnostic Laboratory, Washington State University, Pullman, WA 99164.
| 6 Departments of Veterinary Microbiology and Pathology, College of Veterinary Medicine, Washington Animal Disease Diagnostic Laboratory, Pullman, WA 99164.
| 7 Washington Animal Disease Diagnostic Laboratory, Washington State University, Pullman, WA 99164.