1. College of Veterinary Medicine; Huazhong Agricultural University; Wuhan Hubei China
2. Unit of Animal Infectious Diseases; State Key Laboratory of Agricultural Microbiology; Huazhong Agricultural University; Wuhan Hubei China
3. College of Veterinary Medicine; Northwest A&F University; Yangling Shaanxi China
4. Institute of Animal Husbandry and Veterinary; Wuhan Academy of Agricultural Science and Technology; Wuhan Hubei China