1. Institute for Risk Management in Agriculture and Agricultural Economics Research Institute; Wageningen University and Research Centre; PO Box 8130 6706 KN Wageningen The Netherlands
2. Wageningen University and Research Centre; Hollandseweg 1 6706 KN Wageningen The Netherlands
3. Dutch Udder Health Centre (UGCN); PO Box 2030 7420 AA Deventer The Netherlands
4. Department of Farm Animal Health; Faculty of Veterinary Medicine; Utrecht University; PO Box 80151 3508 TD Utrecht The Netherlands