1. Department of Small Animal Medicine, School of Veterinary Medicine and Animal Sciences, Kitasato University, Towada, Aomori 034-8628, Japan
2. Department of Veterinary Surgery, School of Veterinary Medicine and Animal Sciences, Kitasato University, Towada, Aomori 034-8628, Japan
3. Department of Veterinary Surgery, Faculty of Agriculture, Miyazaki University, Miyazaki 889-2192, Japan