1. Department of Veterinary Science; National Institute of Infectious Diseases; Toyama 1-23-1 Shinjuku Tokyo 162-8640
2. United Graduate School of Veterinary Science Gifu University; 1-1 Yanagido; Gifu 501-1193
3. Laboratory of Veterinary Public Health; Graduate School of Agricultural and Life Sciences; University of Tokyo; 1-1-1 Yayoi Bunkyo Tokyo 113-8657 Japan