Bovine Viral Diarrhea Virus (BVDV) is a Pestivirus of the Flaviviviridae family 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 were defined as PI. We found that only 3/18 herds (16.7%) contained antigen-positive cows, and that only 5/157 animals tested (3.2%) were antigen positive. All of the positive animals were confirmed as PI, and all of PI cows were less than 17 months old. The true prevalence of antigen-positive cows was calculated to be 3.31%. A significant proportion (p<0.01) of PI animals exhibited severe weight loss (4/5; 80%). and before this study, it was supposed to be sent to slaughterhouse by the farmers due to loss of weight. We conclude that the prevalence of PI cows in our study is consistent with previous reports. However, our study reveals that severe weight loss in young PI animals requires their removal to minimize the numbers of BVDV infected animals in the herd.

Keywords