Infection Of Pregnant Sheep Research Articles

Infection of pregnant sheep with the NADL strain of bovine virus diarrhoea virus and their subsequent challenge with Border disease IIB pool

Ten South Country Cheviot ewes were injected intraperitoneally with NADL strain of bovine virus diarrhoea virus (BVD) on the 54th gestational day. At term, one produced a weak hairy lamb with generalized hypomyelinogenesis of the CNS-features characteristic of Border disease (BD) 3 produced non-hairy, normally myelinated offspring with severe intracranial malformations, one aborted and one produced an apparently normal lamb. Four ewes were killed at intermediate stages of gestation and some of the foetuses and placentae had lesions consistent with BD or the early phases of intracranial malformation. The following year the surviving 6 ewes were challenged with a pool of BD infected lamb brain; one produced a BD affected lamb, one a lamb with severe neural and skeletal malformations and one aborted. The other 3 produced normal offspring. The findings emphasize the close similarity between BVD and BD virus diseases and the variable extent of cross immunity between strains. It is suggested that the outcome of infection with these viruses is dependent upon genetic make-up and immune status of the dam and the strain of infecting virus in addition to the gestational age at infection.

Congenital abnormalities in newborn lambs after infection of pregnant sheep with Akabane virus.

Akabane virus (a Bunyavirus) has been associated with epizootics of congenital deformities in cattle, sheep, and goats. Experimental studies using mouse-adapted virus inoculated intravenously into pregnant sheep gave an inapparent infection. Neutralizing antibodies were detected on day 5, and peaks in the titer were seen at days 10 and 48. Ewes infected at day 30 to 36 of pregnancy produced five (31% incidence) deformed lambs. Sera from four of these possessed neutralizing antibodies to Akabane virus before ingesting colostrum. Two lambs had arthrogryposis, hydranencephaly, kyphosis, scoliosis, and brachygnathia; one had micrencephaly; and the other two had porencephaly. The two lambs with arthrogryposis and hydranencephaly also had extensive lesions in other tissues. In the spinal cord there was a marked decrease in the number of ventral horn neurones and a depletion of myelin. Skeletal muscles showed marked atrophy. The medulla of the thymus possessed large Hassall's corpuscles and a reduced number of thymocytes in the cortex. It would appear that the pathogenic effects of Akabane virus are related to the gestational age (30 to 36 days) at which the fetus is infected. Akabane virus can now be included in the growing list of teratogenic viruses and provides an interesting system for studying such congenital diseases.