Visnamaedi Viruses Retroviridae

Opendra Narayan, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA Copyright © 1999 Academic Press

History progressive labored breathing respectively. These diseases broke out in epizootic proportions among Visna and maedi are Icelandic terms for two sheep Icelandic sheep following introduction of European diseases characterized by wasting paralysis and sheep into the local flocks. The newly introduced

Karakul rams had gone through a long pre-importa-tion quarantine period and had come from flocks with no history of the type of disease that broke out in Iceland. These animals were intended to provide a new gene pool for native Icelandic animals which had been maintained in isolation on the island for several centuries. The new diseases spread rapidly among the Icelandic sheep, involving as many as 50% of the animals in some flocks. Maedi was the predominant disease with visna occurring mainly as a complication. The disease complex was finally eradicated from the islands during the 1960s by slaughter of all sheep on the farms that had affected animals. The farms were then restocked with sheep from other parts of the island that had had no contact with the foreign sheep or local sheep with the disease syndromes. Virus obtained from sick animals was the origin of the prototype visna-maedi virus. In 1974, a virus genetically and serologically related to visna-maedi virus was obtained from goats affected with arthritis and encephalitis in Washington State. This virus was named caprine arthritis encephalitis virus (CAEV).

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