1. Shanxi Key Laboratory of Ecological Animal Science and Environmental Veterinary Medicine; Shanxi Agricultural University; Taigu Shanxi 030801 People's Republic of China
2. Chifeng Academy of Agriculture and Animal Husbandry Sciences; Chifeng Inner Mongolia 024031 People's Republic of China
3. Key Laboratory of Zoonosis, Ministry of Education, College of Veterinary Medicine; Jilin University; Changchun Jilin 130062 People's Republic of China