1. Department of Veterinary Pathology,Faculty of Agriculture,Miyazaki University,Nishi 1-1,Gakuen KibanaDai,Miyazaki 889-2192,Japan
2. Department of Virology,The Institute of Medical Science,The University of Tokyo,4-6-1 Shirokanedai,Minato-ku,Tokyo 108-8639,Japan
3. Department of Veterinary Pathology,Faculty of Agriculture,Kagoshima University,1-21-24 Korimoto,Kagoshima 890-0065,Japan