1. Australian Centre for International and Tropical Health and Nutrition, The Queensland Institute of Medical Research, and the University of Queensland, Brisbane, Queensland 4029, Australia1;
2. Hunan Institute of Parasitic Diseases, Yueyang,2 and
3. Academy of Natural Sciences of Philadelphia, Philadelphia, Pennsylvania 191033
4. Institute for Parasitic Diseases, Chinese Academy of Preventive Medicine, Shanghai 200025,4 People's Republic of China; and