1. 1State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, PR China
2. 2Key Laboratory of Preventive Veterinary Medicine of Hubei Province, Huazhong Agriculture University, Wuhan, PR China
3. 3College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, PR China
4. 4Department of Pathology, University of Georgia, Athens, GA, USA