ISOLATION OF SEROTYPE-1 MAREKS-DISEASE VIRUSES FROM VACCINATED AUSTRALIAN FLOCKS

Field samples were received for Marek's disease virus (MDV) isolation from clinically affected flocks from several regions of Eastern Austra lia. Lymphocytes were fractionated in Ficoll-Paque and passaged once o r twice in chicken embryo kidney cultures. Serotype-specific virus was detected in infected cultures by indirect immunofluorescence with mon oclonal antibodies. Serotype MDV was isolated from 10 flocks. In sampl es from 5 of these flocks, serotype 2 and 3 vaccine viruses were isola ted from the same specimen. In a parallel study, plasmas obtained duri ng lymphocyte isolation were tested for antibodies to MDVs by agar gel precipitin (AGP) tests using serotype 1 and 3 antigen extracts. No co rrelation was observed between the rate of virus isolation and AGP pos itivity. The AGP test was incapable of discriminating between the diff erent MDV serotypes.