BROOKINGS, S.D. - Bovine viral diarrhea virus (BVDV) infections are one of the major contributors to bovine respiratory disease (BRD), resulting in losses in U.S. herds estimated at $2 billion per year, according to SDSU professor Chris Chase of the veterinary and biomedical science department.
Since 1996, the Agricultural Experiment Station researcher has been studying BVDV - how it occurs and what it does to sabotage the animal's immune system. "It is an immune-suppressive disease," he explains, making the animal vulnerable to pneumonia and other respiratory diseases.
The virus results in either a transient infection that affects the animal for a few weeks before the immune system fights off the virus; or a persistent infection causing the animal to shed the virus for its entire life.
BVDV controls include vaccinating, monitoring through testing, eliminating persistently infected animals, and quarantining and testing any new animals before they are brought into the herd. Chase adds, "Buying bred heifers or cows is always a big risk because the calf can be infected in utero and we don't have a good way to test for that."
Chase and his colleagues are devoted to better understanding the virus so they can develop a more effective vaccine. A total of 12 graduate students have completed their degrees through research on BVDV over the last 17 years.
In 2003-2004, Chase had access to a group of 136 cows that produced 60 persistently infected calves. The animals provided Chase and his graduate researchers "a gold mine of samples."
They found two viruses and one mutation. In some cases, the virus incorporated part of a cow gene or another virus in the part of the genome in which most mutations take place, Chase explains. This makes developing a vaccine to prevent the virus challenging.
Because BVDV is spread among animals through direct contact, Chase believes the best kind of immunization would be to increase the mucosal immune response - which are the antibodies secreted on the surfaces of the nasal cavity, gastrointestinal and respiratory tracts.
Currently, through a five-year SDSU-USDA Experiment Station project, Chase and his immunology collaborators Alan Young and Adam Hoppe in SDSU's Chemistry and Biochemistry department are examining how BVDV suppresses the cow's immune response. Hoppe's unique imaging system allows the researchers to use fluorescence to see what's happening at a molecular level in live cells.
Their ultimate goal is to understand how persistent infection occurs, which may then lead to developing a more effective vaccine to prevent the BVD virus from infecting the fetus and avoid creating a persistently infected animal that is a threat to the entire herd.
This information was originally published in the SDSU Agricultural Experiment Station 2013 Annual Report.