1. National Veterinary Assay Laboratory, Ministry of Agriculture, Forestry and Fisheries, 1–15–1 Tokura, Kokubunji, Tokyo 185–8511, Japan
2. Department of Veterinary Basic Medicine, Faculty of Agriculture, Iwate University, 3–18–8 Ueda, Morioka, Iwate 020–8550, Japan
3. Department of Veterinary Clinical Medicine, Faculty of Agriculture, Iwate University, 3–18–8 Ueda, Morioka, Iwate 020–8550, Japan