Ovine pulmonary adenocarcinoma in Mexico

Ovine pulmonary adenocarcinoma is a transmissible pulmonary malignancy of sheep caused by a beta-retrovirus currently named Jaagsiekte sheep retrovirus (JSRV). Club cells (formerly Clara cells) in the bronchiole and type II pneumonocytes in the alveoli are the target oncogenic cells for this virus. Characterized clinically by intermittent cough, abundant nasal discharge, and progressive weight loss, the tumors randomly involve all lung lobes or have a cranioventral distribution mimicking bronchopneumonia. The definitive diagnosis of ovine pulmonary adenocarcinoma requires identifying Jaagsiekte sheep retrovirus or associated specific proteins in neoplastic cells such as JSRV-Env oncogenic protein. A two-year-old Male Pelibuey sheep with a history of chronic cough and progressive weight loss was treated unsuccessfully with antibiotics and died a few days later. Postmortem examination revealed lung edema and several nodular to locally extensive masses in the lungs. Microscopically the tumoral tissues were composed of clusters of neoplastic epithelial cells exhibiting a lepidic growth pattern typical of pulmonary carcinoma. Tumoral cells were immunopositive for Jaagsiekte sheep retrovirus-Env oncogenic protein. Based on these findings, the final diagnosis of ovine pulmonary adenocarcinoma was made.