1. Hokkaido Agriculture Mutual Aid Association, Sapporo, Japan
2. Department of Bacteriology, Graduate School of Medicine Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, Japan
3. Laboratory of Anatomy, Department of Basic Veterinary Sciences, Faculty of Veterinary Medicine, Hokkaido University, Hokkaido, Japan
4. Laboratory of Agrobiomedical Science, Faculty of Agriculture, Hokkaido University, Hokkaido, Japan
5. Laboratory of Infectious Diseases, School of Veterinary Medicine, Azabu University, Kanagawa, Japan
6. Laboratory of Theriogenology, Department of Clinical Sciences, Faculty of Veterinary Medicine, Hokkaido University, Hokkaido, Japan