1. Department of Animal Health; Faculty of Veterinary Medicine; University of Parma; Via del Taglio 8 43100 Parma Italy
2. Istituto Zooprofilattico Sperimentale della Lombardia e dell'Emilia Romagna ‘B. Ubertini’; Via Bianchi 7/9 25124 Brescia Italy
3. Laboratory of Virology; Faculty of Veterinary Medicine; University of Ghent; Salisburylaan 133 Merelbeke 9820 Belgium