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. OPA is characterized by symptoms such as coughing, difficulty breathing, and weight loss, often resulting in significant health issues for affected animals. The disease is typically diagnosed through clinical signs, imaging, and laboratory tests. OPA is more common in older sheep and can spread within flocks. Management strategies focus on reducing exposure to the virus and improving overall flock health to prevent the disease's spread.