Detection of Marek's Disease Antigen in Feather Follicle Epithelium of Chickens Vaccinated Against Marek's Disease

Summary

Marek's disease (MD) is a lymphoproliferative disease of chickens caused by a group B herpesvirus. A turkey herpesvirus (HVT) vaccine, injected intra-abdominally or subcutaneously into 1-day-old chicks, protects against development of MD. The vaccine protected birds challenged with Marek's disease virus (MDV) either by contact exposure or parenteral inoculation. Although HVT vaccine prevented tumor development and clinical disease, it did not prevent infection or replication of virulent MDV. MDV was isolated from sonically treated skin samples from vaccinated birds challenged with MDV. Vaccinated birds had both HVT and MDV and antibodies against each. The MD, but not the HVT, antigen could be detected by the direct fluorescent antibody test in the feather follicle epithelium of birds vaccinated at 1 day of age with either the FC126 or WHG-HVT isolates and subsequently challenged with MDV when 3 weeks old. This indicated that vaccinated birds shed virulent MDV in the feather follicle epithelium like unvaccinated, infected birds. One-day-old chicks, given injections of plasma from vaccinated, infected donor birds, containing both HVT and MDV, developed MD lesions. Also, controls reared in direct contact with vaccinated birds developed MD when challenged with MDV.