Diagnosis, characterization, and impact of bovine viral diarrhea virus (BVDV) infection in dairy cattle under field management conditions

The goal of the present research was to provide a better understanding of the epidemiology of BVDV infection in intensively managed dry-lot dairies. The objectives included developing a cost-effective method to identify cattle with BVDV persistent infection (PI), understanding of the decay of BVDV-specific colostral antibodies, estimation of the extent of congenital infection (CI) with BVDV, assess whether BVDV infection affects fertility, and development of a model to identify optimal vaccination programs to minimize BVDV infection in youngstock.; A simulation model was developed to identify the most cost-efficient protocol for pooled-sample testing. The optimal protocol involved re-pooling and splitting of positive pools. Calves can be expected to become seronegative to BVDV type I and type II colostral antibody by 141 and 114 days of age, respectively. Prolonged decay of colostral antibodies was associated with a high initial colostral BVDV titer (P < 0.001) and with CI (P = 0.03). Calfhood BVDV vaccination may prolong BVDV antibodies in calves with failure of passive transfer (P = 0.049). CI was estimated to be 10% and was associated with the dam having a high BVDV type II SN titer (P = 0.035) and being uniparous (P = 0.099). Calves with CI had a higher risk of severe morbidity in the first 45 days of age (P = 0.30). Decreased fertility was associated with high BVDV type II titers at 10–12 months of age (P = 0.013); however, BVDV exposure at 5–6 months of age (P < 0.01) or prior to breeding or conception (P = 0.016) was associated with improved fertility. L. hardjo decreased fertility of heifers with CI but not of those without CI (P = 0.043). BVDV vaccination at 120 days of age and re-vaccination one month later minimized BVDV PNI transmission before first breeding.