1. Division of Viral Disease and Epidemiology, National Institute of Animal Health, National Agriculture and Food Research Organization, 3-1-5 Kannondai, Tsukuba, Ibaraki 305-0856, Japan
2. United Graduate School of Veterinary Sciences, Gifu University, 1-1 Yanagido, Gifu, Gifu 501-1193, Japan
3. Tokushima Animal Hygiene Service Center of Tokushima Prefecture, 5-94 Minamisyoumachi, Tokushima 770-0045, Japan
4. Chuo Livestock Hygiene Service Center, Nagasaki Prefecture, 3118 Kaizu, Isahaya, Nagasaki 854-0063, Japan