1. Pathobiology and Diagnostic Investigation Department, College of Veterinary Medicine, Michigan State University, East Lansing, Michigan, USA
2. Veterinary Diagnostic Laboratory, College of Veterinary Medicine, Michigan State University, Lansing, Michigan, USA
3. National Animal Disease Center, U.S. Department of Agriculture, Ames, Iowa, USA
4. National Veterinary Services Laboratory, U.S. Department of Agriculture, Ames, Iowa, USA