1. Division of Vector-Borne Infectious Diseases, National Center for Infectious Diseases, Centers for Disease Control and Prevention, Fort Collins, Colorado.
2. Institut Pasteur, Département de Parasitologie, Unités de Réponses précoces aux Parasites et Immunopathologie, 25 Rue du Docteur Roux, 75724 Paris Cedex 15, France.
3. Zoonotic Diseases and Emerging Pathogens Section, Laboratory Services, BC Centre for Disease Control, and Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, BC V5Z 4R4, Canada.