The detection of neonatal calves persistently infected (PI) with bovine viral diarrhea virus (BVDV) by common antigen-detection tests is negatively affected by colostral immunity

Reducing exposure of pregnant cattle to bovine viral diarrhea virus (BVDV) by early detection and elimination of persis­tently infected (PI) calves is critical for control and eradica­tion programs. Common test for detection of PI calves such as antigen-capture ELISA (ACE), reverse transcription polymerase chain reaction (RT-PCR), immunohistochemistry (IHC) and the calf-side ELISA snap test (i.e., IDEXX Snap® BVDV antigen test, IDEXX, Fort Collins, CO) are commonly used by producers and veterinarians for the detection of PI cattle. Although most BVDV PI antigen tests are highly sensitive, colostral immunity may in­terfere with test performance leading to false negative results. The objective of this study was to identify the most accurate diag­nostic test, reliable sample type and ideal time for detecting neo­natal PI calves following intake of maternal colostrum.