Bovine Viral Diarrhea (BVD) threatens herd health in a number of ways and can have a major negative impact a dairy’s bottom line. As producers and their advisors meet in the conference room (or kitchen) to discuss BVD, the good news is that combining management and a proper vaccination program with new testing methods can make a difference.
By Tom Shelton, D.V.M.
We didn’t know a lot about BVD when it acquired its name in 1946, and after decades of research and experience, we know today it is often associated with underlying a wide spectrum of diseases. These diseases include sub-clinical infections that are manifested in commonly recognized problems like pneumonia, scours, lameness, mastitis, repeat breeding problems, abortion, mummification of the fetus and congenital defects.
1) When should I be suspicious that I have a BVD problem?
BVD could be the culprit if you notice unexplained animal health challenges or if you run into disease situations beyond the norm.
Ask your veterinarian about additional BVD red flags to look for on your operation and work with your veterinarian to determine if BVD is the underlying problem.
2) I vaccinate my herd regularly for BVD. Why would it still be a problem?
A number of recent studies have looked at the incidence of persistently infected (PI) animals that have been routinely vaccinated. In a number of cases, well-vaccinated herds have had either PI calves or PI lactating cows. While vaccination is critical to BVD protection, if it were 100% effective, we would not be finding this many infected animals.
3) If I can’t count on 100% protection, how can I maximize my vaccination program?
Unborn calves are at risk of developing a persistent infection from 40-120 days of pregnancy. To maximize protection in the dam at this critical time of gestation, an annual booster vaccination should be given 30-45 days post calving. Another common problem that manifests itself as “vaccine failure” may be adding infected animals (or unborn infected calves) to the herd as a result of poor biosecurity measures. For example, it’s common practice to add springer heifers that may be negative themselves for BVD, but are carrying an infected fetus.
To prevent this source of infection, ask your veterinarian about biosecurity measures you should take on your farm.
4) Is BVD a concern after 120 days of pregnancy?
Research has demonstrated that if a cow contracts an acute BVD infection after 120 days of pregnancy, the virus still can infect the unborn calf and have devastating effects. This is called congenital infection, or CI. In addition to a number of congenital abnormalities and abortion, some of these animals are born looking perfectly normal. However, these calves can get acutely sick more than twice as often as unaffected calves, and heifers can be delayed in getting pregnant.
5) What’s the risk of PI compared to CI?
Cows are at risk twice the number of days in gestation for CI compared to PI. For 80 days (from 40 to 120 days), unborn calves are at risk for developing a persistent infection. For 165 days (from 120 to 285 days) unborn calves are at risk for developing a congenital infection.
Talk to your veterinarian about ways to provide fetal protection for the entire pregnancy – for both PI and CI.
6) If we suspect BVD, what testing options do we have?
Testing for BVD within herds and individual animals has progressed greatly. There are now very affordable, accurate tests for bulk milk samples, pooled samples of individual animals and serological monitoring within herds. These new testing procedures have provided a great opportunity to refocus our attention to an insidious problem.
Ask your veterinarian to help you sort out the most cost-effective approach to BVD monitoring and diagnostics.
7) Why is minimizing the effects of BVD so important to the health of my animals?
The way BVD spreads among animals is complex and extensive. It will decrease the overall health of dairy animals and ultimately result in lost production and efficiency. In our quest to raise healthy animals, operate more efficiently and maximize our return on investment, we can’t lose sight of the often hidden scourge, BVD, and remain diligent in our vaccination practices. In addition, new testing methodologies, giving us effective and inexpensive results, have changed the equation for the fight against this costly disease.
• Dr. Tom Shelton is a dairy technical services veterinarian for Intervet/Schering-Plough Animal Health. He lives in Utah and can be contacted by phone: 208-867-3502 or e-mail: firstname.lastname@example.org.