1. College of Agriculture and Animal Husbandry, Qinghai University, Xining 810016, China.
2. College of Animal Science and Veterinary Science, Qinghai University; Qinghai Key Laboratory of Pathogen Diagnosis and Green Prevention and Control Technology for Animal Diseases, Xining 810016, China.
3. State Key Laboratory of Veterinary Etiological Biology, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Lanzhou 730046, China.