The origin of the cytopathic virus can be external, as seen in vaccine associated outbreaks of mucosal disease and in experimental studies. More commonly, however, the cytopathic strain arises from the noncytopathic persistently infecting BVDV by a genetic mutation. Mucosal disease exists in more than one clinical form. Differences in the antigenic relatedness of the noncytopathic and cytopathic BVDV may be responsible for the variations in clinical response. Mucosal disease is characterized by fever, depression, weakness, anorexia and a drop in milk production in lactating cows.
Erosive lesions are usually present throughout the digestive tract.
An article on the control of BVDV infections will be forthcoming in the next issue of the Michigan Dairy Review.