A review of bovine viral diarrhea virus (BVDV) dynamics is followed by a review of test efficiency measures. BVDV diagnostic challenges are then discussed with attention to its pathogenesis during pregnancy and fetal effects. Economic decision theory methods are then applied to evaluate BVDV testing efficiencies and outcomes given certain herd BVDV characteristics.
Two scenarios evaluated are ELISA antibody testing 1) an infected, naive herd, and 2) an infected, 70% immune herd. In the naive herd, 25% of cows were infected in the high risk 60- 120 day of gestation period. This resulted in a 78% calf crop, an 8% persistently infected (PI) prevalence, and where 5% of normal calves had titers. In the 70% immune herd, approximately 8% of cows were infected in the high risk period, resulting in a 90% calf crop, a 2% PI prevalence, and where 1% of normal calves had titers.
The scenarios yielded different test performances. For the naive herd, we were ~56% confident in positive test results, but ~100% confident in negative test results. In the partially immune scenario, these confidences were ~28% and ~100%, respectively. In the naive herd, we falsely culled 3.9 calves, and missed 0.4 PI calves. In the other scenario, the numbers were 3.5 calves, and 0.1 PI calves, or a 10% reduction in false culls, and a 75% reduction in missed PI animals, in spite of the worse test results. This suggests that, though it impairs test performance, the higher a herd’s immunity, we can quantify improved outcomes.
Slenning BD: Proc Am Assoc Bov Pract Conf 36:45-51, 2003.