Host response to bovine viral diarrhea virus and interactions with infectious agents in the feedlot and breeding herd.

Bovine viral diarrhea viruses (BVDV) have significant impact on beef and dairy production worldwide. The infections are widespread in the cattle populations, and in many production systems, vaccinations are utilized. BVDV strains have the hallmark of adversely affecting the immune system's many components, both the innate and acquired systems. While BVDV do cause primary infections and disease, their role in the pathogenesis of other agents underscores the complexity of viral-bacterial synergy. A greater understanding of the role of the persistently infected (PI) animal resulting from susceptible females infected at a critical stage of pregnancy has permitted acknowledgment of a major source of infection to susceptible animals. Not only do we understand the role of the PI in transmitting infections and complicating other infections, but we now focus attempts to better diagnose and remove the PI animal. Vaccinations now address the need to have an immune population, especially the breeding females in the herd. Biosecurity, detection and removal of the PI, and effective vaccinations are tools for potential successful BVDV control.