Marek's disease and new approaches to its control.

Marek's disease (MD) is a lymphoproliferative disorder induced by a herpesvirus. Several factors, including those virus-encoded and host-dependent, affect the course of the disease. Existing vaccination program is based on the use of attenuated strains of MD virus (MDV) serotype 1 and on strains of non-oncogenic serotype 2 (MDV2) and serotype 3 (herpesvirus of turkey-HVT) viruses. Failures resulting in disease progress have been reported and indicate need for production of new, more effective vaccines. It is likely that future development of MD vaccines will rely on recombinant molecules technology.