Congenital malformations in sheep resulting from in utero inoculation of Cache Valley virus.

Serologic evidence indicated that an episode of congenital abnormalities in sheep was caused by Cache Valley virus (CVV), a bunyavirus indigenous to the United States. To determine the teratogenic potential of CVV in sheep, fetuses were infected in utero between 27 and 54 days of gestation with an isolate (CK-102) obtained in 1987 from a sentinel sheep in San Angelo, Texas. The dams of these fetuses were euthanatized between 28 and 75 days after inoculation, and the fetuses were examined for malformations. Twenty-eight of 34 fetuses had congenital abnormalities, including arthrogryposis, hydranencephaly, mummification, reabsorption, and oligohydroamnion. Virus was isolated from the allantoic fluid of 11 of 17 fetuses euthanatized at less than 70 days of gestation. The virus-positive fetuses, which were all negative for CVV-neutralizing antibody, had lesions ranging from none to severe arthrogryposis and hydranencephaly. Virus was not recovered from the allantoic fluid of fetuses after 76 days' gestation when CVV-specific antibody could be detected in 5 of 8 fetuses examined. The 2 fetuses infected on days 50 and 54 of gestation appeared normal and 1 had antibody to CVV.