1a.Objectives (from AD-416):
Determine if there is a correlation between bovine viral diarrhea virus (BVDV) neutralizing antibodies and protection against BVDV exposure in vaccinated calves.
1b.Approach (from AD-416):
Angus beef calves raised under production conditions will be vaccinated with a commercial bovine viral diarrhea virus (BVDV) vaccine. Calves with low, mid range, or high levels of serum neutralizing antibodies following vaccination will be selected. Selected calves will be transferred to the National Animal Disease Center and challenged with a high virulence BVDV. This will be done to determine the level of neutralizing antibodies required for protection.
Under this agreement, NADC was provided with calves, which had been vaccinated and raised in a setting typical of commercial beef production. The goal was to examine the protection afforded by vaccination conducted in a typical production unit using a commercially available vaccine. One of the ways of evaluating the success of vaccination is to measure the level of antibodies present in the blood system before and after vaccination. In previous studies, we had found that not all animals in the herd respond the same way to vaccination. While some generate a lot of antibodies following vaccination a notable proportion generate a very low level of antibodies. The purpose of this project was to determine if animals with a low response were protected from disease. We did this by exposing previously vaccinated calves to one of the pathogens that the vaccine was licensed against. The pathogen used was bovine viral diarrhea virus. All vaccinated calves, regardless of the level of antibodies, did not get as sick as non vaccinated calves. However, those calves with lower antibodies still developed mild clinical signs of infection. Calves with mid range or high levels of antibodies did not get sick. These results indicate that vaccination is effective, but vaccination practices need to be changed/improved to provide protection for the whole herd. One paper detailing these studies has been submitted.