Neurological disorders, virus persistence and hypomyelination in calves due to intra-uterine infections with bovine virus diarrhoea virus. II. Virology and epizootiology.

The results are described of virological and serological research carried out in a Dutch dairy herd during a number of years. The motive was the birth of a number of calves with neurological disorders pointing at an intra-uterine infection with BVD-virus in 1980. Also in the previous and in both the following years a calf was born with similar symptoms. The clinical signs and the course of the affection in these eight calves were described in a previous paper (2). The diagnosis was confirmed through virus isolation from pre-colostral blood of one calf and from autopsy material from four aberrant calves. During the investigation three clinically normal animals with a persistent virus infection were found. The clinically recovered animal of 1979 also provided to be a virus carrier. In addition, in two animals a transient viremia in the presence of specific antibodies was found. The four virus carriers conceived normally. The second pregnancy of the oldest animal also passed normally. Their five calves proved to be BVD-virus carriers as well. One calf, born in 1982, showed nervous disturbances to a serious extent. Of the four other clinically normal animals, one calf was euthanasized because of a serious necrotizing enteritis. The remaining calves stayed healthy and grew up normally. One of the two animals with a transient viremia was five months pregnant at that moment. At birth in 1981 her calf showed nervous disorders, but both the virological and the serological examinations of the pre-colostral blood were negative.(ABSTRACT TRUNCATED AT 250 WORDS)