1. National Institute of Animal Health, Tsukuba, Ibaraki 305-0856, University of Tsukuba, Ibaraki 305-8572, and BIOTECH, University of the Philippines, Los Banos College, Laguna 4031, Philippines
2. National Institute of Animal Health, Tsukuba, Ibaraki 305-0856, and University of Tsukuba, Ibaraki 305-8572, Japan
3. National Institute of Animal Health, Tsukuba, Ibaraki 305-0856, and The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan
4. National Institute of Animal Health, Tsukuba, Ibaraki 305-0856, Japan
5. University of Tsukuba, Ibaraki 305-8572, Japan