1. Division of Environmental Health Engineering, Department of Environmental Health Sciences
2. Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland 21205
3. Division of Parasitic Diseases, National Center for Zoonotic, Vector-borne, and Enteric Diseases, Centers for Disease Control and Prevention, Public Health Service, U.S. Department of Health and Public Services, Atlanta, Georgia 30341
4. Atlanta Research and Education Foundation and Atlanta VA Medical Center, Decatur, Georgia 30333