1. Department of Veterinary Science, National Institute of Infectious Diseases, Tokyo, Japan
2. Laboratory of Veterinary Microbiology, Joint Graduate School of Veterinary Science, Yamaguchi University, Yamaguchi, Japan
3. Department of Pathology, National Institute of Infectious Diseases, Tokyo, Japan
4. Hikiiwa Park Center, Wakayama, Japan
5. Department of Microbiology, Faculty of Veterinary Medicine, Okayama University of Science, Ehime, Japan