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Mini Case Report: Splenomegaly and Hepatomegaly in Backyard Chickens

Two chickens of unknown breed – one adult and one juvenile – were submitted for autopsy. The farm that housed the chickens has a history of sudden death in adult chickens and lethargy, weakness and diarrhea in the younger ones.

Grossly, the main findings were an enlarged spleen in the younger hen and splenomegaly and hepatomegaly in the older chicken. Sciatic nerves appeared normal for both animals. Avian influenza virus swabs were negative, as were bacterial cultures of the livers. Interestingly, Eimeria spp. were noted on fecal float for the older chicken but not for the younger hen with clinical diarrhea.

Microscopically, the older bird had widespread lymphocytic infiltration and effacement in many organs, including in the liver, spleen and lung, consistent with lymphoma (Figures 3a-c). Lymphocyte proliferation also was present in the younger chicken, but it mostly was limited to the spleen, with smaller infiltrates in the tracheal submucosa, esophageal submucosal glands, blood vessel walls in the liver, peripheral nerve, ventriculus, and the lamina propria of the small and large intestines.

Lymphoma is associated with two main viruses in chickens: gallid alphaherpesvirus-2 (Marek’s disease) and the retrovirus avian leukosis virus. Marek’s disease can be seen in chickens of any age group, while avian leukosis typically is seen in chickens more than 14 weeks of age. Given that the younger and older chickens were affected in this case, Marek’s disease was the favored diagnoses. Immunohistochemical staining for T cells was positive (Figure 3d), confirming the diagnosis.

This case report was originally published in the November 2019 VDL newsletter.

Heidi Pecoraro, DVM, PhD, DACVP