1 Centers for Epidemiology and Animal Health, USDA—Animal and Plant Health Inspection Service—Veterinary Services, Fort Collins, CO 80526.
| 2 Present address is 2150 Centre Ave, Building B, Fort Collins, CO 80526-8117.
| 3 Centers for Epidemiology and Animal Health, USDA—Animal and Plant Health Inspection Service—Veterinary Services, Fort Collins, CO 80526.
| 4 Animal Population Health Institute, College of Veterinary Medicine and Biological Sciences, Colorado State University, Fort Collins, CO 80523.
| 5 Department of Environmental and Radiological Health Science, College of Veterinary Medicine and Biological Sciences, Colorado State University, Fort Collins, CO 80523.
| 6 Animal Population Health Institute, College of Veterinary Medicine and Biological Sciences, Colorado State University, Fort Collins, CO 80523.