Transmission of pestivirus infection to sheep and goats in close confinement with a calf persistently infected with a vaccinal strain of bovine virus diarrhoea virus

Abstract

A five months calf persistently infected (P.I.) with a vaccinal strain of bovine pestivirus was confined, for 11 weeks, in close contact with two seronegative goats and two seronegative pregnant sheep in the fourth month of gestation. Transmission of infection was confirmed by a neutralization assay of the cytophatic effect of the Oregon C24V strain on EBTr cells. Goats and sheep seroconverted during the 2nd and 3rd weeks of confinement. Serum antibody titres increased, mainly in the first four weeks, and remained constant after reaching the maximum titers between the fifth and the ninth week. Vaccinal bovine pestivirus strain also infected the two ovine fetuses in a pregnant sheep as was shown by the presence of specific serum neutralizing antibodies before the colostrum intake. Epidemiological implications of using live vaccines in mixed herds are discussed.