Pathology in the ovine foetus caused by an ovine pestivirus.

Homogenised tissues or tissue culture supernatant fluid containing a noncytopathic pestivirus obtained from a lamb with a neurologic form of border disease, were inoculated into ewes at different stages of pregnancy. Foetal death occurred in 9 ewes of those inoculated between 19 and 47 days of pregnancy while 3 ewes did not lamb. Eight of the foetuses were aborted between 77 and 132 days of pregnancy; of these 6 were autolysed or mummified and one had arthrogryposis. The one full-term dead lamb had a hairy birth coat and lissencephalic micrencephaly. Foetal death occurred in only 7 of 14 ewes inoculated between 57 and 72 days of pregnancy. Four of these ewes aborted between 77 and 108 days of pregnancy and 3 gave birth to full-term, dead, hairy lambs. The remaining 7 ewes gave birth to live hairy lambs with severe inco-ordination. All lambs carried to term and aborted foetuses or lambs that could be examined had a range of intracranial malformations including focal leucomalacia, micrencephaly, hydranencephaly, porencephaly, lissencephaly and cerebellar hypoplasia. Some lambs also had skeletal abnormalities including arthrogryposis, scoliosis and brachygnathia inferior. The pestivirus isolate used in these trials produced more severe effects on the ovine foetus than previously observed in similar inoculation trials using pestivirus isolates from border disease lambs without nervous signs.