1. Department of Veterinary Pathology, Nippon Veterinary and Animal Science University, 1-7-1, Kyonan-cho, Musashino, Tokyo 180-8062, Japan
2. Department of Hygiene, Nippon Veterinary and Animal Science University, 1-7-1, Kyonan-cho, Musashino, Tokyo 180-8062, Japan
3. Department of Microbiology, Nippon Veterinary and Animal Science University, 1-7-1, Kyonan-cho, Musashino, Tokyo 180-8062, Japan
4. Department of Internal Medicine, Nippon Veterinary and Animal Science University, 1-7-1, Kyonan-cho, Musashino, Tokyo 180-8062, Japan