Persistently infected (PI) cattle were infected with BVD as a fetus. PI cattle shed large amounts of virus throughout their life.  All calves that are born to PI heifers/cows will be PI as well.  If you have BVD in your herd and choose not to test for PI cattle, controlling BVD in your herd may not be possible.   

It is best to test for PI cattle prior to the breeding season when all, or most of, the cows are open.  It is not necessary to test every cow in your herd in order to find all of the PI animals.  A whole herd test includes testing all calves,  bulls, replacement heifers, and cows that are not currently nursing a calf.  If a pregnant cow tests negative for BVD, she should be kept separate from the herd until she calves and her calf tests negative as well.  The dams of calves that test positive need to be tested.  However, dams of calves that test negative do not need to be tested.

There are several testing options available for BVD PI status. Most tests require a skin sample which is easily supplied by an ear notch.   Contact your veterinarian for details about sample collection and shipment to a laboratory.  Your veterinarian will be able to work with the laboratory to select the specific testing option that best meets your needs. 

Any cattle that are confirmed as BVD PI should be humanely euthanized or sold directly to slaughter.  Read the Academy of Veterinary Consultants BVD position on BVD by clicking on the following link: AVC BVD Position Statement .