1. Center for Infectious Disease Research in Asia and Africa, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan;
2. Nagasaki University Institute of Tropical Medicine-Kenya Medical Research Institute Project, Nairobi, Kenya;
3. Department of Bacteriology, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan;
4. Department of Eco-Epidemiology, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan