1. Department of Veterinary Internal Medicine, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1–1–1 Yayoi, Bunkyo-ku, Tokyo 113–8657, Japan
2. Division of Veterinary Infectious Disease, Department of Veterinary Pathobiology, Nippon Veterinary and Life Science University, 1–7–1 Kyonanchyo Musashino, Tokyo 180–8602, Japan
3. Department of Veterinary Pathology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1–1–1 Yayoi, Bunkyo-ku, Tokyo 113–8657, Japan