title: Milk as a diagnostic sample for a commercially available ELISA to identify bovine viral diarrhoea (BVD) antibodies in dairy herds.
abstract: OBJECTIVE
  The aims of this study were to evaluate a commercially available ELISA for the detection of bovine viral diarrhoea virus (BVDV)-specific antibodies in individual milk compared with individual serum samples, and in bulk milk samples compared with within-herd antibody prevalence and bulk milk quantitative reverse transcription polymerase chain reaction (qRT-PCR) results.
  
  
  METHODS
  Paired individual serum and individual milk samples were collected from 125 lactating cows and tested by ELISA; 96 bulk milk samples were also tested. Within-herd antibody prevalence was calculated based on milk ELISA results for 25 individual cows in each herd. Additionally, 167 bulk milk samples were tested for BVDV-specific antibodies by ELISA and for the presence of BVDV by qRT-PCR to establish the correlation between antibody result and virus presence.
  
  
  RESULTS
  Good agreement was observed between individual milk and serum results (Kappa = 0.865). The ELISA was observed to detect BVDV-specific antibodies in individual milk samples with a relative sensitivity of 96.6% and specificity of 89.2%. The bulk milk samples revealed a strong (r(2) = 0.95) relationship between the ELISA result and the within-herd antibody prevalence. The proportion of herds that tested positive by bulk milk qRT-PCR increased as the bulk milk antibody S/P ratio increased.
  
  
  CONCLUSIONS
  Commercially available ELISA testing of individual and bulk milk samples is an appropriate alternative to serum testing with good test performance in these samples. Determining a threshold for the detection of herds containing active BVD infection by testing bulk milk is a novel use for an antibody ELISA kit and provides more practical, relevant test results.
authors: School of Animal and Veterinary Sciences, University of Adelaide, Roseworthy, South Australia, 5371, Australia. sasha.lanyon@adelaide.edu.au.
authors: S R
authors: SR
authors: Lanyon
authors: R
authors: R
authors: McCoy
authors: E
authors: E
authors: Bergman
authors: M P
authors: MP
authors: Reichel
mesh_terms: D000818:Animals; D000914:Antibodies, Viral; D001912:Bovine Virus Diarrhea-Mucosal Disease / Q000097:blood / Q000175:diagnosis* / Q000453:epidemiology / Q000821:virology*; D002417:Cattle; D001908:Diarrhea Viruses, Bovine Viral / Q000276:immunology* / Q000302:isolation & purification*; D004797:Enzyme-Linked Immunosorbent Assay / Q000662:veterinary; D008892:Milk / Q000821:virology*; D015203:Reproducibility of Results; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000662:veterinary; D014739:Victoria / Q000453:epidemiology
chemical_list: D000914:Antibodies, Viral
keywords: ELISA; PCR; bovine viral diarrhoea; milk