1. Faculty of Veterinary Medicine, Hokkaido University, Sapporo, Hokkaido 060-0818, Japan
2. Animal Research Center, Agricultural Research Department, Hokkaido Research Organization, Shintoku, Hokkaido 081-0038, Japan
3. Rakuno Gakuen University, Ebetsu, Hokkaido 069-8501, Japan
4. Organization for Promotion of Tenure Track, University of Miyazaki, 1-1 Gakuen Kibanadai-nishi, Miyazaki 889-2192, Japan
5. Center for Animal Disease Control, University of Miyazaki, 1-1 Gakuen Kibanadai-nishi, Miyazaki 889-2192, Japan