Investigating the molecular characteristics and pathogenicity of a new strain of the subgroup J of the leukemia virus with the occurrence of polyostotic osteosarcoma in MacQueen's bustard (Chlamydotis McQueen)

Osteosarcoma has been described as a rare primary bone tumor in birds that affects the axial skeleton; Sometimes, it happens in a soft tissue called extraskeletal osteosarcoma.Retroviruses are usually associated with the development of solid tumors in different species of birds. This report aims to describe a case of osteosarcoma with lymphoid leukosis caused by a new mutant of avian leukosis virus subgroup J in a MacQueen's bustard (Chlamydotis McQueen). A female MacQueen bustard with a history of chronic lameness and sudden abdominal swelling for two days died at night. Histopathology revealed an infiltrative mesenchymal neoplasm composed of spindle cells with moderate cellular pleomorphism, organized in clusters and scattered with marked deposition of the osteoid matrix, consistent with osteosarcoma of the femur and tibiotarsus with liver and kidney metastasis. Immunohistochemistry of primary and metastatic tumors showed vimentin expression by neoplastic cells. Neoplasmic Samples from the Kidney, liver, and spleen were processed for PCR, which allowed the demonstration of new mutant DNA from proviral avian leukosis virus subtype J (ALV-J). Furthermore, its inoculation to SPF chickens showed that the viral load of the isolated strain in the immune system organs was significantly higher than HPRS103, and the weight loss, viremia, viral shedding, rate of myocardial fiber rupture, and lymphocyte infiltration into the pulmonary lymphatic vessels were higher. Conclusion The findings of this study have reported the occurrence of osteosarcoma along with investigating the characteristics of a new mutant of ALV-J.