1. Veterinary Epidemiology and Public Health Group, Department of Veterinary Clinical Sciences, Royal Veterinary College, Hatfield, Hertfordshire, United Kingdom.
2. Centre for the Mathematical Modelling of Infectious Diseases and Faculty of Infectious Disease Epidemiology, London School of Hygiene and Tropical Medicine, London, United Kingdom.
3. UR AGIRs, Centre International de Recherche Agronomique pour le Développement, Campus International de Baillarguet, Montpellier, France.