1. National Institute of Animal Health, 3 Kannondai, Tsukuba 305-0856, Japan
2. Kumamoto Central Livestock Hygene Center, 1666 Shidomeniibata, Shimoituki, Kumamoto 961-4215, Japan
3. Kyushu Branch, National Institute of Animal Health, Chuzan, Kagoshima 891-0105, Japan
4. STAFF Institute, Kamiyokoba, Tsukuba 305-0854, Japan