Graciela R Ostera1, James R Blum2, Rojelio Mejia3. 1. Department of Microbiology and Immunology, Georgetown University Medical Center, Washington, DC. Electronic address: osterag@georgetown.edu. 2. Department of Microbiology and Immunology, Georgetown University Medical Center, Washington, DC. 3. Laboratory of Clinical Parasitology and Diagnostics, National School of Tropical Medicine, Baylor College of Medicine, Houston, TX.