1. The United Graduate School of Veterinary Sciences, Gifu University, 1–1 Yanagido, Gifu 501–1193, Japan
2. Department of Clinical Veterinary Science, Obihiro University of Agriculture and Veterinary Medicine, Inada-cho, Obihiro 080–8555, Japan
3. Graduate School of Animal and Food Hygiene, Obihiro University of Agriculture and Veterinary Medicine, Inada-cho, Obihiro 080–8555, Japan