1. Yachiyo Branch Office, Western Veterinary Clinical Center, Chiba Prefectural Agricultural Mutual Aid Association, 2-5-12 Midorigaoka, Yachiyo-shi, Chiba 276-0049, Japan
2. Department of Veterinary Medical Sciences, Graduate School of Agriculture and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan