Marek's disease virus (MDV) is a highly oncogenic cell-associated lymphotropic alpha-herpesvirus which causes Marek's disease (MD)
in domestic chickens worldwide.
MDV is a double stranded DNA virus which is composed of numerous strains with virulence ranging from mild to very virulent. There are also three MDV serotypes which have been denoted as Gallid alphaherpesvirus 2 (GaHV-2), avirulent Gallid alphaherpesvirus 3 (GaHV-3 or MDV-2), and Meleagrid alphaherpesvirus 1 (MeHV-1 or herpesvirus of turkey (HVT)).
MDV replicates in the feather follicle epithelium (FFE) and is spread horizontally through the feather dander, dust, skin cells, and molted feathers. The infectivity of the cell free virus in feather dust can be blocked by commercial air filters.