Clinical and immunologic responses of cattle to vaccinal and natural bovine virus diarrhea virus (BVDV)

by Cortese, Victor Stuart

This research had two objectives. First, to determine ifBVDV vaccines containing type I BVDV were safe and efficacious against a type II BVDV challenge in calves. Second, to determine if modified live BVDV vaccines could stimulate a greater degree of protection against BVDV reproductive syndromes as well as a longer duration of cross neutralizing antibodies than the current inactivated vaccines. One to nine week old cakes were adrninistered modified Iive and/or inactivated BVDV containing vaccines on various schedules. The calves were monitored for adverse effects and foliowed serologically for 12 weeks. BVDV challenge studies were performed in calves vaccinated with either a modified live or inactivated vaccine beginning on day 14 of age. BVDV sero-negative and seropositive calves were included in the study. Studies were performed in BVDV sero-negative cows. Safety was determined by assessing the risk of BVDV transmission of vaccinal virus. Duration of cross neutralizing antibodies stimulated by a single modified live BVDV vaccine was determined. Finally, the ability of a modified live BVDV vaccine to provide fetal protection was assessed. Neither the modified live BVDV vaccines r,ûr the inactivated BVDV vaccine used in these studiss caused adverse reactions in the young calves. Calves with BVDV maternal antib~dy less than 1:64 by virus neutralization testing responded to BVDV vaccination. Calves vaccinated with modified live BVDV vaccine or with high maternal antibody against BVDV were protected from a type