1. Centre for Biodiversity and Environment Research; Department of Genetics, Evolution and Environment; University College London; Gower Street London WC1E 6BT UK
2. Department of Microbiology and Immunology; Tulane University; New Orleans Louisiana USA
3. Institute of Zoology; Zoological Society of London; Regent's Park London NW1 4RY UK
4. Department of Veterinary Medicine; Disease Dynamics Unit; University of Cambridge; Cambridge UK