Ovine pulmonary adenocarcinoma (OPA) is a type of lung cancer that primarily affects sheep. It is caused by the jaagsiekte sheep retrovirus (JSRV), which infects the lung tissue and leads to the formation of tumors. The disease is characterized by symptoms such as coughing, difficulty breathing, and weight loss, often resulting in severe respiratory distress. The cancer is typically diagnosed through clinical signs, imaging, and laboratory tests. OPA is considered contagious among sheep, as the virus can spread through respiratory secretions. Management of the disease focuses on controlling the spread and improving the health of affected animals.