History and current status of Marek's disease in turkeys

Abstract

Marek's disease (MD), caused by a highly contagious and oncogenic herpesvirus, causes immunosuppression and tumors in chickens. Although several reports on the occurring lymphomas (MD-like conditions) in turkeys have been published, less attention has been paid to the disease in this species. Recently, Marek's disease virus (MDV) has been demonstrated in lymphomatous tumors in commercial turkeys in several countries. The present review aimed to describe the past and recent situation of MD in turkeys, including clinical picture and methods used for diagnosis. Additionally, three hypotheses that might explain the emergence of MDV in turkeys, including virus evolution and evolution of MDV variants, modern hybrid turkeys, and raising of turkeys close to chickens, were discussed. The pathogenesis of MDV infection in turkeys remains unclear, and further investigations are necessary. Although herpesvirus of turkey (HVT) vaccine didn't protect turkeys against challenge with a virulent MDV, Rispens strain is effective, highlighting the need for further assessment of the effectiveness of MDV vaccines in turkeys.