Screening of persistently infected cattle with bovine viral diarrhea virus on dairy farms by using milk tanker and bulk tank milk samples for viral RNA and viral-specificantibody detection

摘要

The objective of this study was to provide a screening scheme of persistently infected (PI) cattle on dairy herds by combining reverse-transcription polymerase chain reaction (RT-PCR) todetect bovine viral diarrhea virus (BVDV) in milk tanker samples and commercial enzyme-linked immunosorbent assay to detect BVDV antibodies in bulk tank milk. We conducted a pilot survey andregional survey targeting all dairy farms in Ibaraki Prefecture by using milk tanker and bulk tank milk samples to screen PI cattle. Farms with positive samples underwent a follow-up test toidentify PI cattle. In the pilot study, all virus-positive samples in bulk tank milk were included in the positive milk tanker samples. The RT-PCR assay successfully detected BVDV atdilutions of 1:1,600 by using two PI cows’ milk. In the regional survey, 5 of 79 milk tanker samples were virus-positive. The virus was detected in three PI lactating cows and one PI calf onthree farms. Antibody screening using bulk tank milk samples revealed 15 of 363 samples were positive, and 12 of 348 farms were BVDV antibody-positive. Follow-up tests on one farm identifiedthree PI calves. Thus, eight PI cattle on five farms were identified in this study. In conclusion, combining BVDV detection using milk tanker samples and antibody detection using bulk tankmilk is a feasible and economical method to efficiently screen PI cattle and confirm the PI-free status among dairy herds.