1. Tokachi NOSAI, Hokkaido 089-1182, Japan
2. Department of Veterinary Medicine, Nippon Veterinary and Life Science University, Tokyo 180-8602, Japan
3. Toyonishi Livestock Clinic, Hokkaido 089-1183, Japan
4. Department of Clinical Veterinary Science, Obihiro University of Agriculture and Veterinary Medicine, Hokkaido 080-8555, Japan