was diagnosed as the cause of prolo

was diagnosed as the cause of prolonged high mortality in two commercial flock of chickens by gross and microscopic examination of affected tissues and by immunofluorescent study of live tumor cells using anti-Marek's disease tumor-associated surface antigen, anti-immunoglobulin M, and monoclonal antibodies. The disease was characterized by swollen, necrotic, lymphomatous combs and mortality that rose above normal at 28 weeks of ages, peaked at 35-36 week, and returned to normal by 45-46 weeks.