1. Department of Veterinary Pathology, School of Veterinary Medicine, Kitasato University, 23–35–1 Higashi, Towada, Aomori 034–8628, Japan
2. Veterinary Research Department, Research Institute for Tropical Medicine, Department of Health, 9002 Research Drive, Filinvest Corporate City, Alabang, Muntinlupa City 1781, Philippines
3. Department of Veterinary Science, National Institute of Infectious Diseases, Toyama 1–23–1, Shinjuku-ku, Tokyo 162–8640, Japan