Two Cases of Marek's Disease in Backyard Turkeys.

In two independent submissions, a 3-yr-old, dead Bourbon Red turkey tom from a zoo and a Royal Palm turkey hen from a backyard flock were submitted for necropsy. Both birds had been kept together with chickens. Findings of the necropsy of the first turkey were an enlarged and dark liver with many pale white foci and a few small white nodules, pale and enlarged spleen, prominent thymus, mottled and pale kidneys, and pale and enlarged testes. Findings of the necropsy of the second turkey were a dark and mildly enlarged liver and severely enlarged, firm, and pale kidneys. Histopathology revealed infiltration of most organs of both birds with neoplastic lymphocytes, which were uniform in the first turkey and pleomorphic in the second turkey. Immunohistochemistry with a CD3 marker identified the neoplastic lymphocytes as T cells. Marek's disease virus serotype 1 was detected with PCR in the livers of both birds, whereas PCRs for reticuloendotheliosis virus and lymphoproliferative disease virus were negative. Based on these findings, Marek's disease was diagnosed in both turkeys, which is very rare and were the first definitive cases reported in the United States. It is likely that the chickens were the source of infection.