1. Department of Population Health and Pathobiology, North Carolina State University College of Veterinary Medicine, Raleigh, North Carolina
2. Laboratory of Pathology and Toxicology, University of Pennsylvania School of Veterinary Medicine, Philadelphia, Pennsylvania
3. Rollins Diagnostic Laboratory, Raleigh, North Carolina
4. Department of Biopathological Sciences and Hygiene of Animal and Food Production, University of Perugia, Italy