Marek's disease: an update on oncogenic mechanisms and control

Marek's disease (MD) is a common lymphoproliferative disease of poultry caused by a highly contagious and oncogenic herpesvirus. In spite of the widespread use of highly effective MD vaccines, recently there have been worrying trends in the evolution of MD virus pathotypes towards greater virulence. In the last few years, there has been significant progress in determining the molecular structure of MD virus and several genes that map within the repeat regions of the virus, such as Bam HI-H family, ICP 4, meq and pp38, which are potentially associated with the latency and transformation have been identified. The functions of some of these genes have provided insights into the mechanisms of MD virus-induced oncogenesis. This review summarises some of these oncogenic mechanisms and the progress in the control of MD.