1. Test early-before placing the calves in a group if possible to reduce virus spread and definitely before breeding them as heifers.
2. Test all calves-if positive, euthanize the calf and test the dam. Cull (+) dams.
3. Test any open cow if her calf died or was sold untested. Cull positives.
4. Test all bulls and replacement heifers (purchased or raised). Cull positives.
5. For Pregnant cows-test calf when it is born. If calf is positive, euthanize calf then test cow.
6. Purchased Pregnant Cows-Quarantine and test cow and, if negative, she can join the herd. However, bear in mind her calf could still be a PI. Therefore, when her calf is born, test her calf and if it is positive, euthanize this calf.
7. Any positive test in valuable animals can be confirmed by segregating the animal and retesting blood drawn at least 3 weeks after the first sample. True PI animals will still be positive after 3 weeks. Remember PIs are considered defective and there is a moral and ethical obligation to euthanize and dispose of these animals. They are still considered safe for human consumption.
To control BVDV, effective vaccines are available to combine with management practices in order to prevent/limit its introduction into the herd. For heifers, vaccines should be given 4-6 weeks prior to breeding to reduce the risk of reproductive problems and fetal infection. The lactating herd should receive at minimum an annual vaccination with at least 5 way viral protection. Dairy calves should be vaccinated after 4 months of age; ideally with 2 doses of a modified live vaccine given 4 weeks apart (observe label warnings). Boostering the vaccine to heifers at least 2 weeks before a stressful event such as transport or commingling is beneficial in certain management situations. Consult your veterinarian for specific recommendations for your herd. Other important management practices to reduce the risk of BVDV include:
1. Screen newly purchased cattle for the presence of the virus (submit ear notch or serum) and isolate cattle until the results are known. Remember that pregnant cows may be test negative for BVDV but the unborn fetus may be PI so you must test the cow and her newborn calf.
2. Show cattle should be isolated 3-4 weeks after returning to the farm.
3. Test new bulls before they are used (virus can live in the semen).
4. Prevent potentially BVDV contaminated objects (boots/vehicles/equipment) from entering the premise.
5. Limit wildlife interaction with the cows if possible.
6. Vaccinate the lactating herd annually to maintain immunity in the event of exposure.
7. Manage pastures to minimize fence line contact with other cattle, especially during early pregnancy.
Consult with your local veterinarian on the best way to detect BVDV on your farm as well as to assess the most biologically appropriate and cost-effective control measures. Successful control will result in improved productivity, performance, health, and ultimately economic return.
Source: Michelle Arnold, DVM, University of Kentucky Ruminant Extension Veterinarian