1. The Chemo-Sero-Therapeutic Research Institute, 1-6-1 Okubo, Kitaku, Kumamoto-shi, Kumamoto 860-8568, Japan
2. United Graduate School of Veterinary Science, Yamaguchi University, 1677-1 Yoshida, Yamaguchi 753-8515, Japan
3. Department of Veterinary Medicine, Faculty of Agriculture, Tottori University, 4-101 Koyama, Tottori 680-8553, Japan
4. Veterinary Microbiology, Department of Veterinary Medicine, Joint Faculty of Veterinary Medicine, Kagoshima University, 1-21-24 Korimoto, Kagoshima 890-0065, Japan