Studies of rinderpest virus in pregnant animals

Abstract

A critical review of the literature back to the 18th century revealed that abortion in cattle infected with rinderpest virus has received scant attention despite a handful of early reports of its occurrence. These early reports have been confirmed; three strains of the virus of varying degrees of virulence induced abortion in cattle while attenuated vaccine strains did not. Over 50 per cent of the abortions occurred 2 to 7 weeks following clinical recovery and most foetuses aborted at this stage showed virological and antigenic evidence of in utero transplacental infection with the virus. Foetuses aborted during or soon after the acute stage of the disease had no demonstrable evidence of transplacental infection. Some cows did not abort and delivered normal calves at term, a few of which had pre-colostral serum neutralizing antibodies against rinderpest virus indicating in utero infection.The experimental results were reinforced by a natural attack of rinderpest in the field in which there was a high incidence of abortion in cattle 2 to 4 weeks after the disappearance of the disease.There was no relationship between the age of gestation and the outcome of abortion in cattle. In addition there was no demonstrable evidence for the establishment of a persistent virus infection in the calves born to cows infected before 105 days of gestation.Moderately and highly virulent strains of rinderpest virus were used to determine the time of onset of foetal infection which, with the moderately virulent strain, was first detected on the 17th day after the onset of fever in the dam and on the 5th day following the onset of fever in the case of the highly virulent strain.Evidence of transmission of infection by contact from aborting to susceptible cattle was equivocal.Pregnant goats and rabbits inoculated with virulent strains of rinderpest virus aborted and unlike cattle, most of which aborted several weeks after recovery, abortions in goats and rabbits occurred during or soon after the acute phase of the disease. There was no virological or serological evidence of in utero infection.