1. Department of Production and Population Health; The Royal Veterinary College; Hawkshead Lane, North Mymms Hatfield Hertfordshire AL9 7TA UK
2. Department of Pathology & Pathogen Biology; The Royal Veterinary College; Hawkshead Lane, North Mymms Hatfield Hertfordshire AL9 7TA UK
3. The Royal Veterinary College; Hawkshead Lane, North Mymms Hatfield Hertfordshire AL9 7TA UK
4. Bristol Veterinary School; University of Bristol; Langford House Langford Bristol BS40 5DU UK
5. Centre for Population Health Sciences; University of Edinburgh; Teviot Place Edinburgh EH8 9AG UK
6. Veterinary Epidemiology Consulting; PO Box 80 Mildenhall IP28 9BF UK