Caused by Gallid Herpesvirus-2, Marek’s disease is a highly infectious, wide spread infection in chickens. The viral incubation period is 4-6 weeks and flock mortality is reported to be 10-50%. Infection is most common in young flocks (generally up to 24 weeks age). Clinical signs include hind limb or wing paralysis, dyspnoea, depression, weakness, tumors on feather follicles, blindness and a withered comb. Most clinical signs are associated with the development of T cell lymphoma and the infiltration of lymphocytes into tissues and nerves. Infection with Marek’s disease also causes immunosuppression and increases susceptibility to secondary infections. The virus is shed in the feather dander and droppings or any secretions. Infected birds may not show clinical signs and may shed the virus for long periods, and the virus can persist in poultry yards.
PCR of blood or fresh tissue is the preferred test method for confirmation of infection. Histopathology usually shows typical lymphoproliferative lesions which will suggest infection, which can then be confirmed by PCR.
Vaccines used to control infection in commercial poultry are not routinely available for backyard poultry, and may not be protective against the many virus subtypes circulating.
Blood feathers, fresh tissue (liver or spleen), fixed tissues for histopathology (liver and spleen)
Plain yellow-top container (feathers, fresh tissue)
Formalin pots for histopathological samples
Pluck at least two blood feathers ensuring there is blood visible in the quill. If there are other differentials, consider submitting a full range of post-mortem tissue samples for histopathology.