Maedi Visna virus is a highly contagious and chronic lentivirus that primarily affects sheep. It belongs to the Retroviridae family and is characterized by a slow and progressive inflammatory disease that predominantly impacts the respiratory tract and central nervous system.
The term "Maedi Visna" originates from the Icelandic names of the two major manifestations of the disease. Maedi refers to the respiratory form, while Visna denotes the cerebral form. Though these conditions are distinct, they are caused by the same virus and often occur together.
Infection with the Maedi Visna virus occurs through inhalation or ingestion of virus-containing particles present in respiratory secretions, colostrum, or milk. The virus primarily targets macrophages, a type of immune cell, and causes chronic inflammation in the infected tissues.
Clinical signs of infection may include progressive respiratory distress, characterized by coughing, shortness of breath, and weight loss. In advanced stages, affected animals may exhibit neurological symptoms such as ataxia, paralysis, and behavioral changes. The disease usually presents itself months or even years after the initial infection, and it is characterized by a long incubation period.
There is no known cure for Maedi Visna virus. Management strategies primarily aim at controlling the spread of the disease through culling infected animals, strict biosecurity measures, and hygienic practices. Vaccination programs have shown some efficacy in preventing the spread of this virus, particularly in countries where the disease is prevalent.
