1. Key Laboratory of Animal Disease Control and Prevention of the Ministry of Agriculture, College of Veterinary Medicine, South China Agricultural University, Guangzhou, Guangdong, People's Republic of China;
2. Guangdong Open Laboratory of Veterinary Public Health, Institute of Animal Health, Guangdong Academy of Agricultural Sciences, Tianhe, Guangzhou, Guangdong, People's Republic of China;
3. College of Animal Science, Yangtze University, Jingzhou, Hubei, People's Republic of China