Ovine Pulmonary Adenomatosis, or OPA, is a contagious and invariably fatal viral disease that affects sheep. It is caused by a retrovirus, specifically the Jaagsiekte sheep retrovirus (JSRV). OPA primarily targets the lungs, leading to the development of tumors, typically adenocarcinoma.
In OPA-affected sheep, the retrovirus infects the cells lining the small airways and bronchioles of the lungs. This viral infection stimulates uncontrolled cell growth, resulting in the formation of tumors that obstruct the normal respiratory function. These tumors are primarily composed of neoplastic epithelial cells, which undergo unregulated cell division.
The initial signs of OPA are usually subtle and nonspecific, making the disease difficult to diagnose in early stages. Affected animals may display mild respiratory symptoms such as coughing, labored breathing, and decreased exercise tolerance. As the tumor burden increases, more severe respiratory distress and weight loss can be observed. In advanced stages, the disease may progress to involve other organs, such as lymph nodes, liver, and kidneys.
OPA spreads from infected to susceptible animals through the inhalation of respiratory secretions or dust contaminated with the JSRV retrovirus. The virus can also be transmitted through mutual sharing of equipment, needles, or long-term close contact between infected and healthy individuals.
Due to the highly contagious nature and lack of an effective treatment or vaccine, Ovine Pulmonary Adenomatosis represents a significant economic concern for sheep producers worldwide. Strict biosecurity measures, culling of affected animals, and ensuring a clean environment are fundamental in controlling the spread of the disease.
