1. Department of Joint Veterinary Medicine, Faculty of Agriculture, Tottori University, 4-101 Koyama, Tottori 680-8553, Japan
2. The United Graduate School of Veterinary Science, Yamaguchi University, 1677-1 Yoshida, Yamaguchi, 753-8511, Japan
3. Present address: Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
4. Department of Virology, National Institute of Hygiene and Epidemiology, No. 1 Yersin street, Hanoi, Viet Nam
5. Avian Zoonosis Research Center, Faculty of Agriculture, Tottori University, 4-101 Koyama-Minami, Tottori 680-8553, Japan