Jaagsiekte sheep retrovirus

Jaagsiekte Sheep Retrovirus (JSRV) is a betaretrovirus that causes a contagious lung cancer in sheep known as ovine pulmonary adenocarcinoma (OPA), or more commonly, Jaagsiekte. The disease is characterized by the development of tumors in the lungs, leading to a progressive respiratory failure. JSRV is of significant concern in the sheep farming industry due to its impact on animal health and welfare, as well as its economic implications.

Etiology

JSRV is a retrovirus, which means it is an RNA virus that inserts a DNA copy of its genome into the host cell in order to replicate. This virus specifically targets the cells lining the small airways of the sheep's lungs. The integration of the viral genome into the host cell's DNA can lead to uncontrolled cell division and tumor formation.

Transmission

The primary mode of transmission of JSRV is through the inhalation of aerosolized particles containing the virus, which are produced by infected sheep through respiratory secretions. The disease is highly contagious among sheep, and the close contact within flocks facilitates its spread. Vertical transmission from ewes to lambs has been suggested but is not well documented.

Clinical Signs

Infected sheep may initially show no symptoms, but as the disease progresses, they develop a chronic, progressive respiratory illness. Clinical signs include:

• Weight loss
• Labored breathing or dyspnea
• A notable increase in nasal discharge, which may be frothy
• Reduced exercise tolerance

In advanced stages, the disease can lead to severe respiratory distress and eventually death.

Diagnosis

Diagnosis of OPA caused by JSRV can be challenging due to the similarity of its symptoms to other respiratory diseases in sheep. Diagnostic methods include:

• Post-mortem examination revealing characteristic tumors in the lungs
• Histopathological examination of lung tissue
• Molecular techniques such as PCR to detect JSRV DNA
• Immunohistochemistry to identify viral proteins in tissue samples

Prevention and Control

Currently, there is no vaccine available for JSRV. Control measures focus on preventing the spread of the virus within and between flocks. These measures include:

• Isolating and culling infected animals
• Avoiding the introduction of new animals into the flock without proper quarantine
• Implementing biosecurity measures to reduce the risk of disease transmission

Research and Implications

Research on JSRV has not only focused on understanding and controlling the disease in sheep but also on the implications for human health. JSRV is of interest in the study of lung cancer, as it is one of the few viruses known to induce lung cancer in its host. Studies on JSRV may provide insights into the mechanisms of virus-induced cancer and potential therapeutic strategies.

See Also

• Retrovirus
• Lung cancer
• Sheep farming
• Viral diseases in animals