1. Department of Cattle and Sheep Diseases , National Veterinary Research Institute , 24-100 Pulawy , Poland
2. Institute of Molecular Pathogenesis , Friedrich-Loeffler-Institut , 07 743 Jena , Germany
3. Department of Poultry Diseases, Faculty of Veterinary Medicine , University of Warmia and Mazury , 10-719 Olsztyn , Poland