Figure 1

Pathophysiology of Marek’s disease (adapted from Calnek model [[10],[11]] ). Marek’s disease virus (MDV) enters into the chicken through the respiratory tract. MDV has a tropism for B- and T- lymphocytes as well as for the feather follicle epithelium, from which MDV is shedded into the environment. Feathers, skin danders and dust are the major source of MDV infectious materials and the basis of horizontal bird-to-bird transmission in field conditions.