1. Department of Applied Veterinary Medicine, Obihiro University of Agriculture and Veterinary Medicine, Nishi 2-sen 11 Inada-cho, Obihiro, Hokkaido 080–8555, Japan
2. Veterinary Medical Center, Graduate School of Life and Environmental Sciences, Osaka Prefecture University, 1–58 Rinku Ourai Kita, Izumisano, Osaka 598–8531, Japan