1. Department of Comparative Pathology, Faculty of Veterinary Medicine, Hokkaido University, Sapporo; Department of Veterinary Pathology, Obihiro University of Agriculture and Veterinary Medicine, Obihiro; Department of Veterinary Pathology, School of Veterinary Medicine, The College of Dairying, Ebetsu; and Hidaka Agricultural Aid, Mitsuishi, Hokkaido, Japan