LIC: BVD prevalence in New Zealand’s dairy herd falls below 5%
LIC, a farmer-owned cooperative, introduced commercial BVD screening in 2009, when infection affected as many as 29% of herds in some regions. More than 15 years of control measures have combined regular screening, removal of persistently infected animals and tighter biosecurity. Chin supports establishing a sector-wide eradication framework following the reduction in infections.
New Zealand’s dairy industry eliminated enzootic bovine leucosis in 2009 after a campaign lasting 12 years. That viral infection causes malignant tumours in lymphoid tissue. A separate, decade-long biosecurity partnership targeting Mycoplasma bovis remains on track for eradication by 2028. Current surveillance of bulk milk has recorded no positive detections for that disease. LIC’s leadership cited these programmes as precedents for pursuing BVD elimination.
Persistently infected cattle release large quantities of BVD virus throughout their lives. If a previously unexposed cow becomes infected during her first four months of pregnancy, the virus can pass through the placenta. Outcomes include embryonic loss, fetal mummification, birth defects and persistently infected calves with impaired immunity. Among adult dairy cows, acute infection temporarily weakens immune defences, increasing susceptibility to mastitis and pneumonia and reducing daily milk production.
Diagnostic methods have developed from costly blood sampling of individual animals to PCR testing of bulk milk and tissue-notch sampling. These methods have made surveillance more affordable and accessible to commercial farms. Modelling by the BVD Free Committee puts the annual agricultural cost of endemic infection at approximately $200 million. Its estimate includes forced culling, the expense of raising replacement animals, reduced milk-solids output and poorer reproductive performance. Infected herds also have more dispersed calving dates and lower submission rates during the first six weeks of mating, affecting seasonal pasture use and farm returns.
Chin identified the introduction of an untested bull for natural mating as the greatest single biosecurity threat. Such an animal can introduce infection into a previously clear herd, reversing progress made through screening and culling. The farm-management measures outlined include requiring negative BVD antigen and antibody results before bringing breeding bulls or animals returning from grazing onto the home milking platform. Boundary fencing is another focus of biosecurity precautions.
As New Zealand prepares to move from disease suppression towards elimination heading into 2027, the proposed approach calls for coordination between dairy farmers, veterinary practices and diagnostic cooperatives. Chin’s case for a formal eradication programme combines continued herd surveillance with strict controls on incoming livestock, building on the testing and removal measures already used to reduce infection.
