PATHOGENESIS OF CONGENITAL ENCEPHALOPATHIES IN SHEEP EXPERIMENTALLY INDUCED BY AKABANE VIRUS

Akabane virus strain OBE-1 was inoculated i.v. into 29 pregnant sheep and their fetuses were delivered by hysterotomy at different stages of gestation. Fetuses infected at 29-36 days of gestation developed a severe necrotizing meningo-encephalitis, and at the time of birth 2 lambs had hydranencephaly and arthrogryposis with scoliosis and kyphosis. Histologically, cerebral displacement was observed in 4 of 6 newborn lambs. Fetuses infected at 41-46 days of gestation developed a multifocal encephalitis and cysts in the subcortical white matter; these lesions were identified as porencephaly in 5 of 8 newborn lambs. Ependymal rosettes were commonly found in these lambs. Fetuses infected at 81-91 days of gestation developed focal necrobiosis and gliosis in the white matter 30 days after inoculation. Akabane virus infection may be directly responsible for the encephalopathic lesions. The differences between the lesions may be dependent on the developmental stages of the infected fetus.