School of Veterinary Medicine and Science, University of Nottingham, Leicestershire, United Kingdom.|School of Veterinary Medicine and Science, University of Nottingham, Leicestershire, United Kingdom.|Center for Infectious Disease Dynamics, Department of Biology, Eberly College of Science, The Pennsylvania State University, University Park, Pennsylvania, United States of America.|US Geological Survey, Patuxent Wildlife Research Center, Laurel, Maryland, United States of America.|Department of Biostatistics, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America.|School of Life Sciences, University of Warwick, Coventry, United Kingdom.|Center for Infectious Disease Dynamics, Department of Biology, Eberly College of Science, The Pennsylvania State University, University Park, Pennsylvania, United States of America.|School of Veterinary Medicine and Science, University of Nottingham, Leicestershire, United Kingdom.