Rationale
Bovine viral diarrhea virus (BVDV) is one of the most important viral pathogens of both feedlot and dairy cattle. Depending upon the circumstances, susceptible cattle are either transiently (TI) or persistently (PI) infected.
TI animals are typically infected after birth, and shed relatively low levels of BVDV and for a limited period of time.
Persistent infection is the result of in utero exposure to BVDV. A fetus exposed to BVDV before it is capable of mounting an immune response will be immunotolerant to the BVDV strain it was exposed to in utero. The result of this immunotolerance is lifelong shedding of large quantities of BVDV in excretions and secretions.
Animals to be Tested
Since PI calves are the main source of BVDV transmission, it is important that they are identified as early as possible and removed from the farm. Aborted calves should also be tested for BVDV. Testing heifers is indicated when their calves are determined to be PI or when they have lost their calves. In addition, purchased non-pregnant or pregnant heifers and any bulls that are purchased need to be tested.
High Volume Testing: Pooled Sample Screening and Follow-up Testing
The initial test we use for BVDV screening consists of pooling samples from 12 animals and testing the pooled sample by real-time PCR. When a pool is positive, follow-up testing of those 12 samples is done by individual PCR-based testing . The turnaround time for this test is two to four business days.
Individual animals testing positive need to be retested three to four weeks later to differentiate between PI and true TI animals.
Individual Animal or Low Volume Testing
We offer the IDEXX BVDV SNAP test for this purpose. Sample collection and submission protocols are the same as for the larger volume testing. The turnaround time for this test is one business day. As described above, animals testing positive need to be retested after the initial submission.
Sample Collection and Handling
Sample collection is accomplished using a 5/16 inch, V-shaped ear notching tool. Samples are submitted individually, preferably in 3 x 4 inch ear notch bags which are available through MSU VDL in 1,000 bag cartons. The collected and labeled samples should be stored at refrigerator temperature and sent to the MSU VDL within 72 hours of collection.
Details about proper sample collection, disinfection technique, storage and shipping are found in the Test Catalog.