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Bovine viral diarrhea virus (BVDV) is one of the most commonly encountered and economically important pathogens of cattle in North America. Since the mid-20th century, BVDV has been recognized as a significant cause of disease of the gastrointestinal system. The impact of BVDV on reproduction was not perceived for another 30 years, when the occurrence of persistent infection in imunotolerant cattle was described.
BVDV infections may occur in cattle as acute illness- that is, bovine viral diarrhea (BVD)-or as a generally chronic condition-mucosal disease. When susceptible regnant cattle are infected with BVDV, transplacental infections usually occur. Transplacental infections may lead to embryonic or fetal death and abortion, to developmental defects of organs, or to development of immunotolerance and establishment of persistent Infections. Acute BVDV infections contribute, through inmunosuppression, to causing multifactorial diseases, such as diseases of the respiratory and enteric tracts in susceptible calves.