Prevalence of calves persistently infected with bovine viral diarrhea virus in beef cow-calf herds enrolled in a voluntary screening project

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.

Epidemiology and control of BVD in the U.S

The apparent prevalence of bovine viral diarrhea virus (BVDV) persistently infected cattle has been found to be low in U.S. dairies, beef herds and feedlots. Current management practices within U.S. cattle industries that impact the epidemiology of BVDV infections include purchasing untested cattle, lack of biosecurity procedures, large herd sizes, mixing cattle from multiple sources, high cattle densities in dairy and feedlot operations, synchronous breeding of beef herds, communal grazing and widespread vaccination. Evidence for BVDV infection has been found in farmed and free-ranging wildlife in North America; however the risk of BVDV transmission from wildlife to cattle is not known. The perception of a low prevalence of BVDV herd infections, the unrestricted sale of PI cattle, lack of economic data, intensive marketing of vaccines, reluctance to accept federal regulations, and a "gambler's" attitude among producers are impediments to implementation of a national systematic BVD control program. Since 2004, voluntary BVDV control programs have been organized in nine states reflecting the recognition of BVD as an important and preventable problem in the U.S.