1. 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
2. North Lab, 8–35 Hondoori 2–chome Kita, Shiroishi-ku, Sapporo, Hokkaido 003–0027, Japan