1. Department of Microbiology, Hokkaido University Graduate School of Medicine, Kita-15, Nishi-7, Kita-ku, Sapporo, Hokkaido 060-8638, Japan
2. Department of Parasitology, Graduate School of Medicine, Osaka City University, 1-4-3 Asahi-machi, Abeno-ku, Osaka 545-8585, Japan
3. Osaka Municipal Tennoji Zoological Gardens, 1-108, Chausuyama, Tennoji-ku, Osaka 543-0063, Japan