Bovine Viral Diarrhea Virus Type 1 and Type 2 (BVD)
The majority of BVDV infections are subclinical, with severity of disease determined by strain virulence and host susceptibility. However, BVDV infections almost always produce some degree of immunosuppression determined by virulence of the infecting strain. If the animal is exposed to other pathogens while it is immunosuppressed, morbidity and death -loss can be greatly increased. Initial infection is in the respiratory or vaginal mucosa, followed by systemic viral replication and widespread infection of the immune, respiratory, reproductive, and enteric systems. Infected cattle shed BVDV in various body fluids and tissues including saliva, nasal discharge, blood, feces, urine, and aborted fetal tissues. Persistently infected animals can shed more viruses and for longer periods than acutely infected cattle.