The authors Stephen W. Barthold, DVM, PhD, Diplomate ACVP, is a Distinguished Professor, Emeritus in the Department of Pathology, Microbiology and Immunology, UC Davis School of Veterinary Medicine in Davis, California, USA. Denise M. Imai, DVM, PhD, Diplomate ACVP, is a Health Sciences Clinical Professor and Vice Chair of the Department of Pathology, Microbiology and Immunology, UC Davis School of Veterinary Medicine in Davis, California, USA.