1. National Institute of Animal Health, National Agriculture and Research Organization, 3-1-5 Kannondai, Tsukuba, Ibaraki 305-0856, Japan
2. Nakasorachi NOSAI, 1-5-14 Omachi, Takikawa, Hokkaido 073-0022, Japan
3. Souya Livestock Hygiene Service Center, 8-3 Midorigaoka, Hamatonbetsu, Esashi, Hokkaido 098-5738, Japan
4. Hokkaido Research Station, National Institute of Animal Health, National Agriculture and Research Organization, 4 Hitsujigaoka, Toyohira, Sapporo, Hokkaido 062-0045, Japan