It has been almost 20 years since persistent infection with noncytopathic BVDV was reported. This condition occurs when a fetus is infected with noncytopahic BVDV during the first four months of development. Usually, the fetal infection follows an acute infection of a susceptible heifer or cow. For most midwestern beef herds, this means the dam was infected with BVDV during the summer or early fall.
Persistent infection lasts for life.
Persistently infected cows give birth to persistently infected calves. Persistently infected bulls seldom sire persistently infected calves. Persistently infected cattle spread disease, and it is desirable to eliminate them from a herd. This can be done by testing for persistent infection or by vaccinating the herd for BVD at regular intervals. Using the latter approach takes longer, but it is effective and economical.