1. Department of Clinical Veterinary Science; Veterinary Medical Teaching Hospital; Obihiro University of Agriculture and Veterinary Medicine; Obihiro Hokkaido 080-8555 Japan
2. Department of Pathobiological Science; Veterinary Medical Teaching Hospital; Obihiro University of Agriculture and Veterinary Medicine; Obihiro Hokkaido 080-8555 Japan
3. Chuo Veterinary Clinical Center; Engaru District Agricultural Mutual Aid Association; Yubetsu-cho Monbetsu-gun Hokkaido 093-0731 Japan
4. Veterinary Medical Teaching Hospital; Obihiro University of Agriculture and Veterinary Medicine; Obihiro Hokkaido 080-8555 Japan