[1] Univ Bologna, Dept Vet Publ Hlth & Anim Pathol, Fac Med Vet, I-40064 Ozzano Dell Emilia, BO, Italy
[2] Dept Agr & Rural Dev No Ireland, Virol Sect, Vet Sci Div, Belfast BT4 3SD, Antrim, North Ireland
[3] Univ Saskatchewan, Western Coll Vet Med, Dept Vet Microbiol, Saskatoon, SK S7N 5B4, Canada
[4] Ohio State Univ, Coll Vet Med, Dept Vet Biosci, Columbus, OH 43210 USA