1. Department of Biocontrol; Veterinary and Agrochemical Research Centre (VAR) - Ukkel; Groeselenberg 99 B- 1180 Brussels Belgium
2. Department of Bacteriology and Immunology; Veterinary and Agrochemical Research Centre (VAR) - Ukkel; Groeselenberg 99 B- 1180 Brussels Belgium
3. Central Veterinary Services; WTC III, Simon Bolivarlaan B- 1000 Brussels Belgium
4. Veterinary Services of Limburg; B-3500 Hasselt Belgium