1. Department of Veterinary Pathology, Faculty of Agriculture, Iwate University, Morioka, Iwate, Japan
2. National Institute of Animal Health, Tsukuba, Ibaraki, Japan
3. Laboratory of Gene Technology and Safety, Tsukuba Life Science Center, Institute of Physical and Chemical Research (RIKEN), Tsukuba, Ibaraki, Japan
4. Department of Veterinary Microbiology and Pathology, College of Veterinary Medicine, Washington State University, Pullman, WA