1. Department of Veterinary Pathology, Companion Animal Diagnostics, Institute of Comparative Medicine, Bearsden Road, Glasgow Scotland G61 1QH, UK
2. Dip Patologia Animale Igiene, e Sanita Pubblica Veterinaria, Via Celoria 10, Milano I-20133, Italy
3. Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, 2108 Tupper Hall, Davis, CA 95616, USA