1. Liverpool School of Tropical Medicine; Pembroke Place Liverpool L3 5QA U.K.
2. Amani Medical Research Centre, National Institute for Medical Research; Muheza Tanzania
3. Departamento de Parasitologia, Instituto de Ciências Biológicas; Universidade Federal de Minas Gerais; Belo Horizonte Brazil
4. London School of Hygiene and Tropical Medicine; Keppel Street London WC1E 7HT U.K.