1. Key Laboratory of the Provincial Education, Department of Heilongjiang for Common Animal Disease Prevention and Treatment, College of Veterinary Medicine, Northeast Agricultural University, Harbin, Heilongjiang 150030, China
2. Liaoning Agricultural Technical College, Yingkou, Liaoning 115009, China
3. College of Veterinary Medicine, Henan Agricultural University, Zhengzhou, Henan 450002, China