Bovine Viral Diarrhoea Virus (BVDV) is a worldwide distributed infectious disease of cattle. This Pestivirus of the Flaviviviridae can cause economical losses. The aims of this study were to estimate the prevalence of Bovine Viral Diarrhoea Virus (BVDV) antigen positive in dairy cattle herds, and evaluate the significance of the associated between the BVD positive antigen animals and culled cows referred to slaughterhouse in Mashhad-Iran. Totally, 157 individual blood samples were taken from 18 Holstein dairy cattle herds in suburb of Mashhad-Iran. Forty-one (26.11%) out of the total samples were prepared from culled animals referred to slaughterhouse in suburb of Mashhad. They were examined for the presence of BVDV antigen using Pestivirus-Ag capture ELISA. The results showed that 5 (3.18%) animals tested were antigen positive. Only one herd had one antigen positive cow. The infected cow retested after 3 weeks which was positive again. However, 4 infected antigen positive cows were detected from the slaughter house. All the positive BVDV aged less than 17 months old. The calculated true prevalence of antigen positive was 0.18%. The differences between BVD antigen positive in slaughter house cows and dairy cattle herds were significantly higher (P<0.01). It was concluded that the prevalence rate of positive BVD virus cows were not more than the other studies. It is likely that the positive cows were PI animals which were culled from the herds to be referred to slaughterhouse.

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