Affiliation: | a Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO 63110, USA b Animal Parasitic Disease Laboratory, Animal and National Resources Institute, Agricultural Research Service, United States Department of Agriculture, Beltsville, MD 20705, USA c Department of Microbiology, University of Tennessee, Knoxville, TN 37996, USA d Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge, CB2 1QP, UK |