1. School of Veterinary Medicine and Science and School of Mathematical Sciences; University of Nottingham; Sutton Bonington Campus Sutton Bonington LE12 5RD
2. School of Clinical Veterinary Science; University of Bristol; Langford Bristol BS40 5DU
3. Ecology and Epidemiology Group; Department of Biological Sciences; University of Warwick; Coventry CV4 7AL