Colostrum-derived immunity reduces detection of calves persistently infected with bovine viral diarrhea virus by common diagnostic tests.

Abstract

OBJECTIVE: This study aimed to compare the most accurate sample type, test, and timing for detecting bovine viral diarrhea virus (BVDV) in persistently infected (PI) calves at different time points following birth and colostrum intake. METHODS: Thirteen 18-month-old pregnant heifers were inoculated with BVDV 1b at approximately 75 days of gestation to induce PI offspring. Serum, nasal swabs (NS), and ear notch (EN) samples were collected from PI and negative control calves from birth until day 28 after colostrum intake. Serum immunoglobulin G and BVDV 1b neutralizing antibodies were assessed, and the BVDV detection probability of antigen-capture ELISA (ACE), reverse transcription quantitative PCR (RT-qPCR), virus isolation, and Idexx SNAP test was evaluated using stepwise mixed-effects generalized linear models. RESULTS: 10 PI calves were born. Colostrum-derived BVDV 1b antibodies markedly inhibited BVDV detection, producing false-negative results in up to 100% of samples from PI calves during the first week of age. Total serum immunoglobulin G concentration did not influence BVDV detection. The probability of detecting BVDV in EN samples by RT-qPCR, ACE, and Idexx SNAP increased in PI calves after 7 days of age; however, virus isolation and serum-based tests remained less dependable due to a higher incidence of false negatives. CONCLUSIONS: Colostrum-derived BVDV antibodies suppressed BVDV detection in PI calves during the first week of life, leading to false-negative results with various sample types and tests. CLINICAL RELEVANCE: Evaluating EN samples with RT-qPCR, ACE, or Idexx SNAP after 7 days of age allowed reliable detection of PI calves in the face of colostrum-derived immunity.