Visna-maedi

Visna-maedi, also known as ovine progressive pneumonia (OPP), is a retroviral disease of sheep that primarily affects the lungs and central nervous system. It is caused by the Visna-maedi virus (VMV), a member of the Lentivirus genus of the Retroviridae family. The disease is characterized by progressive pneumonia, wasting, and nervous system disorders.

Etiology

The causative agent of Visna-maedi is the Visna-maedi virus (VMV), a Lentivirus that is part of the Retroviridae family. VMV is closely related to the Caprine arthritis encephalitis virus (CAEV), which causes a similar disease in goats.

Epidemiology

Visna-maedi is found worldwide, but its prevalence varies greatly between countries and regions. It is most common in countries with large sheep populations, such as Iceland, where it was first identified. The disease is transmitted primarily through respiratory secretions, but can also be spread through milk and colostrum.

Clinical Signs

The clinical signs of Visna-maedi can vary greatly, but typically include progressive weight loss, difficulty breathing, and neurological signs such as tremors and paralysis. The disease is slow-progressing, and infected animals may not show signs for several years.

Diagnosis

Diagnosis of Visna-maedi is typically based on clinical signs and confirmed by laboratory testing. The most common tests used are serological tests, which detect antibodies to the VMV virus in the blood.

Treatment and Control

There is currently no cure for Visna-maedi, and treatment is primarily supportive. Control measures include testing and culling of infected animals, and preventing contact between infected and uninfected animals.

See Also

• Sheep
• Lentivirus
• Retroviridae
• Caprine arthritis encephalitis virus

Visna-maedi Resources
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