1. Epizootic Research Station, Equine Research Institute, Japan Racing Association, 1400-4 Shiba, Kokubunji-machi, Shimotsuga-gun, Tochigi 329-0412, Japan
2. National Institute of Animal Health, 3-1-1 Kannondai, Tsukuba, Ibaraki 305-0856, Japan
3. Hidaka Livestock Hygiene Service Center, Kousei-cho, Shizunai-cho, Shizunai-gun, Hokkaido 056-0005, Japan