1. Water Quality Laboratory, Engineering Department, Kobe City Waterworks Bureau, 37-1 Kusutani-cho, Hyogo-ku, Kobe 652-0004, Japan
2. Department of Parasitology, Faculty of Health Sciences, Kobe University Graduate School of Health Sciences, 7-10-2 Tomogaoka, Suma-ku, Kobe 654-0142, Japan