1. Department of Medical Zoology, Faculty of Medicine, Kagoshima University, Kagoshima 890, Japan
2. Department of Parasitology, Institute of Tropical Medicine, Nagasaki University, Nagasaki 852, Japan
3. Centre for Microbiology Research, Kenya Medical Research Institute, Ministry of Health, Nairobi, Kenya
4. Division of Vector Borne Diseases, Ministry of Health, Nairobi, Kenya