the prevalence of bovine viral diarrhea virus in persistently infected cows in industrial dairy herds in suburb of mashhad- iran

bovine viral diarrhea virus (bvdv) is a pestivirus of the flaviviviridaefamily that infects cattle, and its widespread distribution can cause substantial economic losses worldwide. the aims of this study were: (1) to estimate the prevalence of animals persistently infected (pi) with bvdv in industrial dairy cattle herds in suburb of mashhad- iran; and (2) to compare the occurrence of persistently infected (pi) animals in industrial dairy cattle herds where bvdv animals had been either removed from or retained in the herds. in total, 157 blood samples were taken from individual cows from 18 holstein dairy cattle herds each containing 250-3000 cows in suburb of mashhad. the blood samples were analyzed for the presence of bvdv using pestivirus antigen-capture elisa. positive animals were retested after three weeks and animals those tested positive again weredefined as pi. we found that only 3/18 herds (16.7%) containedantigen-positive cows, and that only 5/157 animals tested (3.2%) wereantigen positive. all of the positive animals were confirmed as pi, andall of pi cows were less than 17 months old. the true prevalence ofantigen-positive cows was calculated to be 3.31%. a significantproportion (p