1. The United Graduate School of Veterinary Sciences, Faculty of Applied Biological Sciences; Gifu University; Gifu Gifu 501-1193 Japan
2. Laboratory of Zoonotic Diseases, Division of Veterinary Medicine, Faculty of Applied Biological Sciences; Gifu University; Gifu Gifu 501-1193 Japan
3. Department of Virology I; National Institute of Infectious Diseases; Shinjuku-ku Tokyo 162-8640 Japan