EN
Infection with bovine viral diarrhea virus is widespread in cattle populations all over the world and thus results in significant economic and breeding losses in herds of various sizes. The studies were conducted on 270 dairy cattle herds that have never been vaccinated against BVDV. Altogether 3732 samples were tested. Antibodies to BVDV were detected in 53.9% of herds. The correlation between herd size and seroprevalence was statistically significant and equal to 0.319 (p < 0.001). Analysis of clinical signs of BVD commonly observed in dairy cattle made it possible to conclude that a sudden drop of milk yield (OR = 2.037), diarrhea in calves (OR = 1.422), emaciation in young animals (OR=1.774) and emaciation in adults (OR = 1.715) were observed much more frequently in infected than uninfected herds. No increase was noted in the occurrence of other clinical signs regarded as typical for infected herds, such as spontaneous abortions and fetopathies in cows or respiratory and alimentary tract disorders.