1. Faculty of Veterinary Medicine; University of Liège; B-4000 Liège Belgium
2. Vetsuisse Faculty; University of Bern; CH-3012 Bern Switzerland
3. Association Régionale de Santé et d'Identification Animales; B-4431 Loncin Belgium
4. Veterinary and Agrochemical Research; B-1180 Brussels Belgium
5. Federal Agency for the Safety of the Food Chain; B-1000 Brussels Belgium
6. B-4987 La Gleize Belgium
7. B-4701 Kettenis Belgium