Visceral lymphomas due to co-infection of Marek's disease virus- avian leukosis virus A-E in Japanese silkie fowl

[Abstract] Increased mortality was noticed in an 8-month-old farm of white silkie fowl (Gallus gallus domesticus) during March 2013. Three birds were necropsied and investigated to determine the etiology. Splenomegaly, hepatomegaly, and enlarged kidneys, testes, and pancreas were observed. Surface mottling or white-tan nodules (5-10 mm) were observed on parenchymatous organs. Peritoneal thickening was noticed in two cases. Lymphomatous lesions comprising diffusely proliferating smallto-medium lymphocytes and large lymophoblasts in some areas and multicentric foci of large lymphoblastic cells almost of the same size were observed in most of the visceral organs in all three birds including spleen, liver, kidneys, heart, lungs, testes, and ovaries. Immunolabeling with Marek's disease virus (MDV) pp38 antibody identified the pp38 antigen in lymphocytes within splenic lymphomatous foci. The lymphomatous foci in spleen, liver, lungs, kidneys, and intestine were positive for CD3 (T-cell marker), and negative for CD20 (B-cell marker) and Pax5 (B-cell transcription factor). PCR amplification of the 132 base pair tandem repeat (BamH1-H, D fragments) of MDV and gp85-env gene of avian leucosis virus subgroups A-E (ALV A-E) in formalin-fixed paraffin-embedded tissues of lymphomas in all three birds yielded 434 and 300 bp amplicons, respectively. Visceral lymphomas due to MDV-ALV A-E co-infection are reported for the first time in Japanese silkie fowl.