Abstract
Field samples were received for Marek's disease virus (MDV) isolation from clinically affected flocks from several regions of Eastern Australia. Lymphocytes were fractionated in Ficoll-Paque and passaged once or twice in chicken embryo kidney cultures. Serotype-specific virus was detected in infected cultures by indirect immunofluorescence with monoclonal antibodies. Serotype 1 MDV was isolated from 10 flocks. In samples from 5 of these flocks, serotype 2 and 3 vaccine viruses were isolated from the same specimen. In a parallel study, plasmas obtained during lymphocyte isolation were tested for antibodies to MDVs by agar gel precipitin (AGP) tests using serotype 1 and 3 antigen extracts. No correlation was observed between the rate of virus isolation and AGP positivity. The AGP test was incapable of discriminating between the different MDV serotypes.