1. Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health; Rockville MD 20852
2. Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University; Bangkok 10400 Thailand
3. Centre for Tropical Medicine, Nuffield Department of Medicine, University of Oxford; Oxford OX3 7BN United Kingdom