Abstract
1 Department of Veterinary Public Health and Food Safety, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820 Merelbeke, Belgium
2 Danish Veterinary Institute, Bülowsvej 27, 1790 Copenhagen V, Denmark
3 Laboratory of Microbiology, Faculty of Sciences, Ghent University, K. L. Ledeganckstraat 35, 9000 Ghent, Belgium
4 Veterinary and Agrochemical Research Centre, Groeselenberg 99, 1180 Brussels, Belgium