1. National Institute of Animal Health, NARO, 3-1-5, Kannondai, Tsukuba, Ibaraki 305-0856, Japan
2. Department of Biosciences, College of Science and Engineering, Kanto Gakuin University, 1-50-1, Mutsuura-Higashi, Kanazawa-ku, Yokohama 236-8501, Japan