1. Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Greifswald-Insel Riems, Germany (Heenemann, Lapp, Teifke, Fichtner, Mettenleiter, Vahlenkamp)
2. Institute of Virology, Faculty of Veterinary Medicine, University of Leipzig, Leipzig, Germany (Heenemann, Vahlenkamp)