Maedi-visna, or ovine progressive pneumonia, is an infectious viral disease of sheep and goats. The disease can take two forms, which get their names from the Icelandic words for difficulty breathing (maedi) and wasting (visna).

The maedi form is the most common manifestation of the disease. It affects the lungs and causes difficulty breathing. The visna form is rare. It affects the central nervous system. Both forms of the disease are fatal.

The maedi-visna virus is transmitted most often from ewe to lamb through ingestion of milk or colostrum contaminated with the virus. It is also believed that the virus can be transmitted among adult animals through inhalation of virus or ingestion of feces-contaminated water.

Maedi-visna is an economically significant disease due to premature culling of animals and export restrictions.

Endemic Areas

The maedi-visna virus is found worldwide. Only Australia, New Zealand and Iceland are considered free of the disease.

Clinical Signs

Maedi

• Increasing difficulty breathing
• Coughing
• Nasal discharge
• Enlarged, firm udder with little or no milk

Visna

• Hindlimb weakness
• Incoordination
• Muscle tremors
• Progressive paralysis
• Weight loss

Treatment

There is no specific treatment for maedi-visna, and the mortality rate approaches 100 percent. Any animal suspected of having maedi-visna should be reported to the State Veterinarians or USDA Area Veterinarian in Charge immediately.

Prevention

Maedi-visna can be prevented by following sound biosecurity practices, including quarantining animals of unknown health status and feeding newborns colostrum and milk known to be free of the virus.

Public Health

Maedi-visna is not a public health threat.

Links

Maedi-Visna -Iowa State University