1. Department of Pathology, Bacteriology and Avian Diseases; Faculty of Veterinary Medicine; Ghent University; Merelbeke Belgium
2. Department of Morphology; Faculty of Veterinary Medicine; Ghent University; Merelbeke Belgium
3. Norwegian Veterinary Institute; Oslo Norway
4. Department of Microbiology and Parasitology; Universidade de Santiago de Compostela; Santiago de Compostela Spain
5. Animal Sciences Unit - Aquatic Environment and Quality; Institute for Agricultural and Fisheries Research (ILVO); Ostend Belgium
6. Department of Environment and Health; Vrije Universiteit; Amsterdam The Netherlands