1. Farm Animal Health Unit, Department of Population Health Sciences, Faculty of Veterinary Medicine, Utrecht University, 3584 CL Utrecht, The Netherlands
2. Vion Food Group, 5281 RM Boxtel, The Netherlands
3. Wageningen Bioveterinary Research, 8221 RA Lelystad, The Netherlands
4. Royal GD, 7418 EZ Deventer, The Netherlands