1. Department of Pathology, University of Georgia, Athens, GA, USA
2. Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, WA, USA
3. Animal Disease Research Unit, Agricultural Research Service, United States Department of Agriculture, Pullman, WA, USA
4. Washington Animal Disease Diagnostic Laboratory, Washington State University, Pullman, WA, USA
5. Department of Veterinary Clinical Sciences, University of Georgia, Athens, GA, USA
6. Ruminant Diseases and Immunology Research Unit, National Animal Disease Center, Agricultural Research Service, United States Department of Agriculture, Ames, IA, USA