The dirty muzzle and watery eyes of this calf are first signs of bovine respiratory disease. The virus lowers the animal’s immune response and makes it susceptible to other respiratory diseases.
Looking at the two genomes of BVDV reveals differences in the NS23 segment between noncytopathic (NCP) and cytopathic strains. Experiments reveal that infection in utero involving the NCP genome can lead to persistently infected calves.