VISNA-LIKE DISEASE IN A RAM WITH CHRONIC DEMYELINATING ENCEPHALOMYELITIS

摘要

A 2-year-old Columbia ram was examined because of a slowly progressive weakness in the hind limbs and weight loss. Examination of CSF obtained from the lumbosacral space revealed mononuclear cell pleocytosis (80 cells/mu l), high protein concentration (100 mg/dl), and high creatine kinase activity (88 U/L). Because of continued deterioration and lack of response to treatment with anti-inflammatory agents and antibiotics, the sheep was euthanatized, and a necropsy was performed. Histologic examination of the brain revealed lesions characteristic of visna, an encephalitis of sheep caused by the maedi-visna virus, an ovine lentivirus. Using the agar gel immunodiffusion test, stored CSF was subsequently found to have positive results for a closely related ovine lentivirus, ovine progressive pneumonia virus. Maedivisna virus could not be isolated from viral cultures of processed semen or stored CSF.