Affiliation: | a Department of Preventive Veterinary Medicine, College of Animal Science and Veterinary Medicine, Shandong Agricultural University, Tai An, Shandong 271018, China b China Animal Health and Epidemiology Center, Qing Dao, Shandong 266000, China c Veterinary Immunobiology Research Institute of Northwest A & F University, College of Veterinary Medicine, Northwest A & F University, Yangling, Shaanxi 712100, China |