1. Department of Parasitology and Tropical Medicine, Seoul National University College of Medicine, Seoul 110-799, Korea.
2. Department of Internal Medicine, Seoul National University College of Medicine, and Institute of Endemic Diseases, Seoul National University Medical Research Center, Seoul 110-799, Korea.
3. Department of Parasitology, Kangwon National University College of Medicine, Chuncheon, Gangwondo 200-701, Korea.
4. Department of Parasitology and Catholic Institute of Parasitic Diseases, College of Medicine, Catholic University of Korea, Seoul 137-701, Korea.