Caprine arthritis-encephalitis virus isolated from Michigan goats.

A syncytium-forming agent with reverse transcriptase activity was isolated in cell culture from materials collected from 19 Michigan goats and 1 goat recently imported from California. Syncytia formation could be maintained by subpassaging cells or filtered supernate from infected cultures with caprine fetal synovial membrane indicator cells. Electron microscopy by negative staining with ammonium molybdate revealed 100-nm retrovirus-like particles morphologically identified as caprine arthritis-encephalitis virus. The agent was recovered from synovial membrane explants, synovial fluid, colostrum cells, and peripheral blood mononuclear cells of clinically arthritic goats. Samples were collected from 9 Michigan goat herds, and virus was isolated from 7 of these herds.