BVD IN NEW ZEALAND

BVD is widespread

• 95% of dairy herds show evidence of past exposure (BVD antibody detectable in bulk tank milk)
• At of 2015, approx. 60% of dairy herds were “actively infected” (s:p >0.75)

Contact with PI animals is the source of active BVD infection. So, BVD control requires two phases:

• Find and eliminate PIs
  • Monitoring
  • Culling PIs
• Prevent new PIs from being created
  • Biosecurity
  • Vaccination

MONITORING

BVD antibody testing

• Blood or milk samples from >9 animals
• Indicates herd’s level of past exposure to PIs
• Higher group antibody = more recent & widespread PI exposure
• S:P > 0.75 means there may be a PI in contact with the herd now: “active” BVD infection

BVD virus testing

• Blood, milk or body tissue (ex: ear notch) from one or more animals
• A positive test means an animal which has been tested is either a PI or is transiently infected
• Isolate and retest positive animals (or cull them straight away)
• Cull all confirmed PIs ASAP — they will always be a source of BVD infection!
• Get vet involved to find PIs or possible sources of PI contact

BEST PRACTICE MONITORING & CULLING PROGRAM FOR DAIRY FARMS:

1. Bulk milk testing
   • Antibody (s:p): 2-3 times per year
   • Virus test (PCR): necessary if bulk milk antibody is >0.75, or has gone up significantly since last test. Recommended 1-2 times per year, before mating, when all cows are contributing to the vat
   • Get vet involved: if you need to find a PI or a source of PI contact, they will be able to help!
2. Calf & purchased/leased animal testing
   • Virus test (PCR or Antigen ELISA) blood samples or ear notches
   • Cull/reject any PI animals you find
   • This checks how well your biosecurity and vaccination programs are working
3. Service bulls
   • Virus test (PCR or Antigen ELISA) blood samples or ear notches
   • Vaccinate (sensitiser & booster) 1 month before mating

REFERENCES

1. Weir, A. (2016). Epidemiology of BVD in New Zealand dairy herds. Massey University PhD thesis dissertation.
2. Hill, F et al. (2010). Testing of pooled sera to predict the BVDv infection status of cattle. VetScript. 05/2010: 38-39.
3. MC Gates, CA Evans, C Heuer, H Voges & JF Weston (2021) Temporal trends in bulk tank milk antibody ELISA and PCR test results for bovine viral diarrhoea in New Zealand pastoral dairy herds, New Zealand Veterinary Journal, 69:2, 73-82.

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