Infection studies on a reticuloendotheliosis virus contaminant of a commercial Marek's disease vaccine.

Reticuloendotheliosis virus (REV) was isolated in cell cultures from commercial Marek's disease (herpesvirus of turkeys) vaccine and re-isolated from the organs of vaccinated chickens. Runting and feathering abnormalities were produced when 1-day-old specific pathogen free chickens were inoculated with REV. Histopathological lesions in infected chickens were hypoplasia of the thymus, bursa and spleen, and inflammation of the proventriculus, kidneys and liver. Serological responses to REV were detected by the indirect immunoflorescence test in chickens directly inoculated with contaminated vaccine, and spread of REV infection to in-contact chickens was demonstrated by histopathological and serological investigations.