SEVERE RESPIRATORY-DISEASE IN DAIRY-COWS CAUSED BY INFECTION WITH BOVINE RESPIRATORY SYNCYTIAL VIRUS

Outbreaks of severe respiratory disease caused by bovine respiratory s yncytial virus (BRSV) were recorded in dairy herds throughout Sweden i n 1988 and subsequently. The virus was demonstrated in nasopharyngeal swab material from animals in the acute stage of the disease by cultur e, the polymerase chain reaction (PCR) and by immunofluorescence. Sero logical data from the herds investigated showed that the cows had sero converted to BRSV rather than to bovine coronavirus, bovine viral diar rhoea virus or parainfluenza-3 virus. It was predominantly dairy herds in isolated areas that contracted a severe primary BRSV infection, of ten after the purchase of new animals. A nationwide survey for BRSV an tibodies in bulk milk samples showed the highest prevalence, of 84 to 89 per cent, in the southernmost regions of Sweden and the lowest prev alence, of 41 to 51 per cent, in the north of the country. The prevale nce of BRSV was highest in areas with the highest populations of cattl e.