1. Division of Epidemiology and Public Health, School of Medicine, University of Nottingham, Nottingham NG 1PB, UK
2. Department of Veterinary Science, University of Pisa, San Piero a Grado, 56122 Pisa, Italy
3. RTI International, Washington, DC 20005, USA
4. Department of Veterinary Sciences, University of Turin, Largo Paolo Braccini, 10095 Grugliasco, Italy
5. Candioli Pharma S.R.L., S.da Antica di None, 10092 Beinasco, Italy