1. Division of Nutritional Sciences, Cornell University, Ithaca, New York 14853
2. Department of Parasitology, Molteno Institute, Cambridge University, Cambridge, CB2 3EEEngland
3. Medical Services, Ministry of Health, P.O. Box 30016, Nairobi, Kenya
4. Nutrition Department, Medical Research Center, a department of the Kenya Medical Research Institute, P.O. Box 20752, Nairobi, Kenya