Andrew Brooks

Animal Health Laboratory, University of Guelph, Guelph, ON.

AHL Newsletter 2024;28(4):15.

In the fall of 2024, a 1.5-year-old Silkie chicken was submitted to the AHL for postmortem examination. Clinically, the hen was keeping distant from the other birds, was not walking normally, and could not stand straight. The feces from the chicken were dark and had an abnormal odor. The bird had a previous history of respiratory signs.

At postmortem, the body cavity of the chicken contained hundreds of small, tan to white, miliary nodules throughout the mesentery and serosal surfaces. The kidneys were diffusely discolored white-tan and were enlarged. The liver also contained white-tan foci that appeared to accentuate the portal architecture. The ovary contained regressing follicles as well as multiple masses. The spleen was enlarged, had a firm texture and was diffusely pink on cut section. Histologically, the main finding was a myeloid cell population that had infiltrated several organs (Fig. 1). The myeloid cells were immature and exhibited a high nuclear:cytoplasmic (N:C) ratio and eosinophilic cytoplasmic granules. There were approximately 1-3 mitotic figures per 400x field. The myeloid proliferation affected the thymus, heart, lung, kidney, liver, spleen, ovary, oviduct and serosal surfaces of the intestinal tract, consistent with a diagnosis of systemic myeloproliferative disease.

This case of myeloproliferative disease is suspected to be a form of avian leukosis associated with the avian leukosis sarcoma group of retroviruses (ALSV), particularly myelocytomatosis associated with ALSV subgroup J (1). Further testing on this chicken was not performed, however, infection with ALSV may be detected by PCR or antigen ELISA.   AHL

Figure 1. Myeloproliferative disease in a Silkie chicken characterized by diffuse infiltration (*) of kidney (A) and liver (B) by immature myeloid cells (inset). H&E stain.

Reference

1. Zavala G. Avian leukosis. In: Brugère-Picoux J, et al. Manual of Poultry Diseases, English edition. AFAS;2015:227-236.