1. Department of Veterinary Microbiology and Preventive Medicine; Iowa State University; Ames IA 50011 USA
2. Department of Veterinary Diagnostic and Production Animal Medicine; Iowa State University; Ames IA 50011 USA
3. Microbiology Laboratory; Hangzhou Center for Disease Control and Prevention; Hangzhou Zhejiang 310021 China
4. Department of Veterinary Pathology; Iowa State University; Ames IA 50011 USA