MaediVisna

MaediVisna is a chronic, progressive, and ultimately fatal disease affecting sheep and goats. It is caused by a retrovirus, the MaediVisna virus (MVV), which belongs to the lentivirus genus, the same genus as the virus that causes AIDS in humans. The disease is widespread globally in sheep and goat populations.

The virus is primarily transmitted through direct contact, with infected colostrum or milk being a major source of infection for newborns. Aerosol transmission is also possible. MVV infects cells of the immune system, particularly macrophages, leading to a slow and persistent infection.

Clinical signs of MaediVisna vary depending on the affected organ system. In sheep, the most common manifestation is a progressive pneumonia, often referred to as "maedi," characterized by dyspnea (difficulty breathing) and weight loss. In goats, a neurological form, "visna," is more prevalent, causing hindlimb weakness, paralysis, and ataxia (incoordination). Other forms of the disease can affect the mammary glands (mastitis) and joints (arthritis).

Diagnosis is typically made through serological tests that detect antibodies against MVV in blood or milk. There is no cure for MaediVisna, and treatment focuses on supportive care to manage symptoms. Prevention strategies involve identifying and culling infected animals, implementing biosecurity measures, and raising lambs and kids separately from infected dams. Many countries have eradication programs to control the spread of the disease.