1. Exotic Disease Research Division, National Institute of Animal Health, 6–20–1 Josuihoncho, Kodaira, Tokyo 187–0022, Japan
2. United Graduate School of Veterinary Sciences, Gifu University, 1–1 Yanagido, Gifu 501–1193, Japan
3. Hokkaido Research Station, National Institute of Animal Health, 4 Hitsujigaoka, Toyohira, Sapporo, Hokkaido 062–0045, Japan
4. Hokkaido Kushiro Livestock Hygiene Service Center, 127–1 Otanoshike, Kushiro, Hokkaido 084–0917, Japan
5. Hokkaido Rumoi Livestock Hygiene Service Center, 6–1 Motomachi, Horonobe-cho, Teshio-gun, Hokkaido 098–3217, Japan
6. Hokkaido Hidaka Livestock Hygiene Service Center, 2–88–5 Shizunai-asahi-cho, Shinhidaka-cho, Hidaka-gun, Hokkaido 056–0003, Japan
7. Hokkaido Iburi Livestock Hygiene Service Center, 4–3 Tomiura, Noboribetsu, Hokkaido 059–0463, Japan
8. Department of Veterinary Medicine, Faculty of Agriculture, Iwate University, 3–18–8 Ueda, Morioka, Iwate 020–8550, Japan