Mareks disease(MD) is a lymphoproliferactive disease of chicken caused by highly infectious cell-asscioated oncogenic alpha-herpesvirus MD virus serotype 1 (MDV 1),characterized by lymphoproliferactive infiltration in visceral organs,muscles,and peripheral nerves.Recently MD has been well studied mainly because of two reasons.One is the heavy economic losses worldwide from MD following industrial poultry farming system in the 1950s and 1960s.The other is the important position of MDV on tumorigencity and vaccine prevention from malignant neoplasm.Because MDV is the first herpesvirus proved to be oncogenic with the experiment.