1 Key Laboratory of Animal Epidemiology and Zoonosis, Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University, Beijing, China.
2 Institute of Veterinary Medicine, Jiangsu Academy of Agricultural Sciences, Nanjing, China.
3 Key Laboratory of Animal Epidemiology and Zoonosis, Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University, Beijing, China pingh_liu@163.com suzhang@cau.edu.cn.
4 Department of Surgery, Duke University School of Medicine, Durham, North Carolina, USA.