Fowl pox is a mild to severe, slow-developing disease of birds caused by avipoxvirus. The disease is
characterized by wart-like nodules on the skin and diphtheritic necrotic membranes lining the mouth and
upper respiratory system. In domestic poultry, infections cause an economically important disease. Active
immunity develops following natural infection or after immunization with live vaccines. Replication of the
vaccinal virus at the inoculation site results in development of a local inflammatory process also known as
vaccinal ‘take’. The presence of vaccinal ‘take’ is an indication that the bird was vaccinated.