1. Yokohama City Meat Inspection Center, 3–53 Daikoku, Tsurumi, Yokohama, Kanagawa 230–0053, Japan
2. Department of Pathology, Azabu University, 1–17–7 Fuchinobe, Sagamihara, Kanagawa 229–8501, Japan
3. Hokkaido Research Station, National Institute of Animal Health, 4 Hitsujigaoka, Toyohira, Sapporo, Hokkaido 062–0045, Japan