1. Department of Obstetrics; Reproduction and Herd Health
2. Department of Pathology, Bacteriology and Poultry Diseases
3. Department of Virology, Parasitology and Immunology; Faculty of Veterinary Medicine; Ghent University; Salisburylaan 133 9820 Merelbeke Belgium
4. Institute of Animal Pathology; Vetsuisse Faculty; University of Berne, Postfach; Länggassstrasse 122 3001 Berne Switzerland