1. Department of Basic Veterinary, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, People's Republic of China.
2. Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Chengdu, People's Republic of China.
3. Department of Aquaculture, College of Animal Science and Technology, Sichuan Agricultural University, Chengdu, People's Republic of China.