[1] Univ Vet Med, Istvan U 21, H-1078 Budapest, Hungary
[2] Lakat Vet Bt, Budapest, Hungary
[3] NFCSO VDD Dept Virol, Budapest, Hungary
[4] Michigan State Univ, Dept Radiol, E Lansing, MI 48824 USA
[5] Univ Illinois, Dept Pathobiol, Coll Vet Med, Urbana, IL 61802 USA