1. Department of Zoonoses, Kitasato University School of Veterinary Medicine, Towada 034-8628, Japan
2. College of Veterinary Medicine, Huazhong Agricultural University, Wuhan 430070, China
3. Research Center for Drug and Vaccine Development, National Institute of Infectious Diseases, Tokyo 162-8640, Japan
4. College of Veterinary Medicine, Southwest University, Chongqing 400715, China
5. Laboratory of Veterinary Anatomy, Kitasato University School of Veterinary Medicine, Towada 034-8628, Japan