VisnaMaedi

VisnaMaedi is a chronic, progressive, and fatal lentiviral disease affecting sheep and goats. It is caused by the small ruminant lentivirus (SRLV), a type of retrovirus. The disease manifests in several forms, most commonly as visna (a neurological form) and maedi (a pulmonary form). These forms can occur together or independently. The virus is transmitted primarily through direct contact with infected animals, particularly via respiratory secretions and milk. Transmission from an infected mother to her offspring is also a significant route of spread.

The incubation period for VisnaMaedi is long, often spanning months to years, making early detection challenging. Symptoms vary depending on the affected organ system. Visna primarily affects the central nervous system, leading to progressive neurological signs such as hind limb weakness, incoordination, tremors, and eventual paralysis. Maedi targets the respiratory system, causing chronic pneumonia characterized by labored breathing, coughing, and weight loss. Other forms can affect the mammary glands (mastitis) and joints (arthritis).

Diagnosis is typically made through serological testing to detect antibodies against SRLV, and further confirmed by molecular methods like PCR to detect viral RNA or DNA. There is no cure for VisnaMaedi, and treatment focuses on supportive care to manage symptoms, though this does not alter the disease's progressive nature. Prevention strategies revolve around biosecurity measures, including isolating new animals, testing and culling infected individuals, and implementing strict hygiene protocols. The economic impact of VisnaMaedi on the sheep and goat industries is considerable due to reduced productivity, mortality, and trade restrictions.