A: A solid vaccine program is significant for protection against BVD. An immunized animal has a better chance of not forming a PI than a non-vaccinated animal.
An idea for a surveillance program would be:
Step 1: Survey presence of BVD in your milking herd by checking the bulk tank milk quarterly. Running the bulk tank test every few months will ensure the testing of all cows (i.e., some may be dry at the time of testing) and will monitor the introduction of either newly purchased animals and/or new heifers to the milking line.
Step 2: If the bulk tank is positive, break down the herd in groups by string sampling to determine which group(s) has a positive. Then, at some point individual cows need to be tested using either an individual ear notch, serum or milk sample.
Step 3: Continue surveillance by testing all:
- Newborn calves (heifers and bulls, and aborted, stillborn or dying calves)
- Purchased animals
- Clean-up bulls
Now, if an ear notch comes back positive:
- The animal should be isolated if possible (a minimum of ten feet and with separate access to water and feed).
- A confirmatory sample should be taken from the PI positive animal three weeks after the original test. If the test is positive again, that animal is a BVD-PI. If the test is negative, that animal was acutely exposed to the BVD virus.
- The PI animal needs to be eliminated from the herd. Once a PI animal, always a PI animal. PI animals should be humanely euthanized.