1. National Institute of Animal Health, 3-1-1 Kannondai, Tsukuba, Ibaraki 305-0856, Japan and Kihoku Livestock Hygiene Service Station, 1291 Sonobe, Wakayama, Wakayama 640-8483, Japan
2. National Institute of Animal Health, 3-1-1 Kannondai, Tsukuba, Ibaraki 305-0856, Japan and3)Gunma Livestock Health Laboratory, 2425-3 Kogure, Fujimi-mura, Seta-gun, Gunma 371-0103, 3)Gunma Livestock Health Laboratory, 2425-3 Kogure, Fujimi-mura, Seta-gun, Gunma 371-0103, Japan
3. National Institute of Animal Health, 3-1-1 Kannondai, Tsukuba, Ibaraki 305-0856, Japan
4. Chiba Prefectural Federation of Agricultural Mutual Aid Associations, 1533 Watarido, Narutou-aza, Narutou, Sanbu-gun, Chiba 289-1326, Japan
5. Chiba Prefectural Institute of Animal Health, 497 Iwatomi, Sakura, Chiba 285-0072, Japan