1. Department of Veterinary Population Medicine, College of Veterinary Medicine, University of Minnesota, St. Paul, MN 55108, USA
2. State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan 430070, PR China
3. Vaccines Clinical Research and Development, GlaxoSmithKline Vaccines, Cambridge, MA 02139, USA
4. Veterinary Diagnostic Laboratory, College of Veterinary Medicine, Manhattan, KS 66506, USA