1. Research Center for Food Safety, The University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo 113-8657, Japan
2. Food Safety Commission of Japan Secretariat, Akasaka Park Bld. 22F, Akasaka 5-2-20, Minato-ku, Tokyo 107-6122, Japan
3. Cooperative Department of Veterinary Medicine, Graduate School of Veterinary Sciences, Iwate University, Morioka-shi, Iwate 020-8550, Japan