Bovine viral diarrhea (BVD) virus can have a severe negative impact on the reproductive efficiency of cow-calf herds. It can also suppress the immune system of calves and can initiate bovine respiratory disease. One of the largest sources of potential BVD infection comes from exposure to animals that are persistent carriers of the virus. These animals are called persistently infected or more simply, PIs. The PIs are animals that are born with the disease and constantly shed the BVD virus in large amounts thus exposing the BVD to their herd mates. It is very important that producers use diagnostic testing to identify PI animals and remove them from the herd.
You can’t tell outwardly if an animal is a BVD PI by simply looking at it, so it requires a sensitive diagnostic test, such as Polymerase Chain Reaction (PCR), to identify these PI animals. PCR is an ideal test to use to find PI animals because it can use either blood or tissue (ear notches) as a sample; can be completed in a very short period of time; and provides very accurate results.