1. Natural Sciences and Science Education, National Institute of Education, Nanyang Technological University, 1 Nanyang Walk, Singapore 637616, Singapore, Department of Chemistry, University of Waikato, Private Bag 3105, Hamilton 3205, New Zealand, Swiss Tropical and Public Health Institute, Parasite Chemotherapy, Socinstrasse 57, PO Box, CH-4002 Basel, Switzerland, and University of Basel, CH-4003 Basel, Switzerland