Bovine Viral Diarrhea – Persistently Infected (BVDV-PI)
Testing is Crucial First Step
It is impossible to prevent BVD-PI if infected animals are in your herd; therefore, testing for BVD is a crucial step in eliminating BVD.
BVD infections can negatively affect:
- conception rates
- pregnancy rates
- milk production
- overall dairy operation profits
While BVD is a challenging disease to control, it can be addressed with proper management. Vaccinating and testing cattle are two ways to start battling BVD. Always follow proper bio-security measures. Animals that are positive for BVD should be isolated and removed from the herd as soon as possible.
It would be unethical to sell a BVDV-PI positive animal on the open market (livestock auction, private sale, etc) unless the seller notifies potential buyer(s) of PI status. Appropriate disposition of BVDV-PI positive animals include:
- Euthanasia (humanely killed)
- Kept separate from all negative animals and fed to finish (risk of death prior to reaching finiah weight)
- Sell to slaughter (upon clearance of withdrawal times)
Economic Impact of BVD
Some producers think they can’t afford to test for BVD, but really you can’t afford not to test.
- Dairies exposed to BVD had 26% higher bulk milk somatic cell counts
BVD impacts cost of gain, feed conversion, weight gain and mortality of pen mates and cattle in adjacent pens
- Feed yard studies show a loss of $31-$41 per head across entire feed yard in productivity
- U.S. Veterinarians estimate that BVD costs producers more than $30 per head each year in productivity and this is after cattle are vaccinated
PI versus TI
Persistently Infected (PI) cattle are born with the disease. A PI positive calf does not always have a PI positive mother. In fact, the mother will be PI negative 90 % of the time. Pregnant cows are most vulnerable from 30 to 150 days gestation. If the mother is exposed to BVD (transmitted from other cattle) during that time, the fetus can be infected.
Unfortunately, once an animal is identified as a BVD-PI, that animal is always infected and no vaccine can cure it. PI cattle cannot be identified by sight alone. At times, some of the healthiest “looking” calves are actually infected with BVD. The only way to determine their health status is by testing them.
Cattle that are transiently infected (TI) are exposed to BVD from another TI or PI animal. They will shed the virus, but not to the extent of a PI. A BVD TI infected calf will shed 10,000 viral particles per day and will recover in 10 to 14 days. A BVD PI infected calf sheds 10 million viral particles every day.
After a few days to a few weeks, a TI infected animal will eventually fight off the virus, but could be susceptible to other diseases. While vaccines help keep TI cattle healthy from BVD, a PI calf can overwhelmingly infect those vaccinated. This risk emphasizes the importance of implementing a testing protocol.