1. b Department of Parasitology , Okayama University Medical School , Shikata, Okayama , 700 , Japan
2. a Faculty of Pharmaceutical Sciences, Okayama University , Tsushima, Okayama , 700 , Japan
3. c Institute for Biotechnology Research, Wakunaga Pharmaceutical Co., Ltd. , Shimokotachi, Koda, Takata, Hiroshima , 729-64 , Japan
4. d Department of Medical Zoology , Nagoya University School of Medicine , Showa, Nagoya , 466 , Japan