Correspondence:
Prof Z-G Yuan, College of Veterinary Medicine, South China Agricultural University, Guangzhou, Guangdong Province, PR China; Y-S Mahmmod, Infectious Diseases, Department of Animal Medicine, Faculty of Veterinary Medicine, Zagazig University, Zagazig, Sharkia, Egypt; A/Prof X-X Zhang, College of Agriculture, South China Agricultural University, Guangzhou, Guangdong Province, PR China
Email: ziguoyuan@scau.edu.cn; yasserpcr@gmail.com; xiuxiangzh@scau.edu.cn