1. Sekiyado Branch Office, Western Veterinary Clinical Center, Chiba Prefectural Federated Agricultural Mutual Aid Association, 462-11 Kirigasaku, Noda-shi, Chiba 270-0213, 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