Affiliation: | 1. College of Veterinary Medicine, Northeast Agricultural University, Harbin, Heilongjiang, P.R. China Heilongjiang Key Laboratory for Animal Disease Control and Pharmaceutical Development, Harbin, China;2. State Key Laboratory of Veterinary Etiological Biology, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Lanzhou, China;3. College of Veterinary Medicine, Northeast Agricultural University, Harbin, Heilongjiang, P.R. China |