1. Cooperative Department of Veterinary Medicine, Faculty of Agriculture, Iwate University, Morioka 020-8550, Japan
2. United Graduate School of Veterinary Science, Gifu University, Gifu 501-1193, Japan
3. Veterinary Clinical Training Center, Miyagi Prefectural Federation of Agricultural Mutual Aid Association, Miyagi 981-3602, Japan
4. School of Veterinary Medicine, Rakuno Gakuenn University, Hokkaido 069-0836, Japan