Injection-Site Sarcoma in Three Village Weaver Birds (Ploceus cucullatus) Associated with Autogenous Yersinia pseudotuberculosis Vaccination.

Post-vaccinal sarcomas have been reported in cats and rarely in other domestic mammals, but not in birds. Three village weaver birds (Ploceus cucullatus) presented with poor flying ability and abnormal wing carriage attributable to large, unilateral pectoral masses. All had received at least one dose of autogenous Yersinia pseudotuberculosis vaccine into the affected pectoral muscle 74-408 days previously. Following euthanasia, gross post-mortem examination revealed locally invasive subcutaneous tumours extending through the sternum into the coelomic cavity. Cytology and histology revealed neoplasms of pleomorphic spindloid neoplastic cells with foci of coagulative necrosis and cavitation, sometimes containing faintly refractile non-polarizing granular material, both extracellularly and after phagocytosis by surrounding cells, including multinucleated giant cells. Immunohistochemistry in one bird supported a striated muscle cell origin. Findings of anaplastic sarcoma with intralesional foreign crystalline material resembled typical injection-site sarcomas in cats. This is the first report of presumptive vaccine-associated sarcoma in a non-mammalian species.