1. Veterinary Diagnostic Laboratory, 1800 Denison Avenue, Kansas State University, Manhattan, KS 66506, USA
2. Department of Diagnostic Medicine and Pathobiology, 1800 Denison Avenue, Kansas State University, Manhattan, KS 66506, USA
3. Merck Animal Health, 2 Giralda Farms, Madison City, NJ 07940, USA
4. Departments of Biology and Microbiology and Veterinary and Biomedical Sciences, South Dakota State University, Brookings, SD 57007, USA