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Bovine viral diarrhoea (BVD) is one of the most economically significant viral diseases of cattle in New Zealand.
DairyNZ estimates the annual BVD-related losses for dairy farmers at $127 million, equating to approximately $70,000 for an average-sized infected herd of 431. That's an average of $162 per cow.
BVD is a Pestivirus that primarily affects cattle. Reports have shown that due to persistently infected (PI) animals' ability to shed the BVD virus's rapidly, it's estimated that about 80 per cent of New Zealand's dairy and beef herds have been exposed. (DairyNZ, 2019).
Three types of infection can result from the disease: acute (transient), foetal and persistent.
Persistently infected cattle are the number one cause of new infections (including foetal infections) due to their shedding of enormous amounts of the virus via all body fluids.(Reichel et al., 2018).
BVD in cattle can cause infertility, abortion, reduced milk production, increase susceptibility to Bovine respiratory disease and other illnesses, increased calf deaths and increased congenital defects.
Often there are no signs of a problem at all. However, in all cases, BVD infection negatively impacts production and increases economic loss. The early detection and immediate removal of PI animals is, therefore, an essential step in all BVD control program.
As the effects of BVD often look like those of other diseases, knowing your BVD status is crucial in the fight to achieve control and maximise productivity and profitability.
Simple diagnostic testing plans are fundamental to making informed decisions to control and prevent the spread of the BVD virus.
BVD control consists of two critical mechanisms that, together, break the within-herd transmission cycle: the early identification and removal of PI animals; and strict herd biosecurity to prevent the reintroduction of the BVD virus from outside sources (Han et al., 2018).
Detecting PI animals is and should remain, the primary focus of all farmers working to remove BVD from their properties.
A breakthrough 2019 research trial done in New Zealand by Cognosco Animal Health demonstrated that farmers now have a superior BVD testing method available to them for calves, the IDEXX BVD antigen ELISA on ear-notch.
Listen to Jamie Mackay's interview with Andrew MacPherson on The Country below:
The trial tested the sensitivity (ability not to miss a PI) and specificity (ability not to falsely call a calf positive) of ear notch samples of calves. The results showed that you can now not only effectively control BVD regardless of age, but you can also minimise unnecessary calf culling with the IDEXX test.
The IDEXX test is available through your veterinarian and is unique in that it targets a very specific area of the BVD virus called the Erns structural unit of the virus.
Results of the trial demonstrated an economical breakthrough with Andrew MacPherson, IDEXX Medical Affairs Veterinarian quoted saying "we now have the perfect test to focus our efforts on identifying only PI animals (i.e. using the IDEXX antigen ELISA test) thereby saving unnecessary culling of animals that are not PI's testing falsely positive using other methods. This will enable farmers to maximise their return on the calves born each year".
Today, effective BVD control by targeting all calves born in New Zealand is entirely achievable and economically beneficial.
Testing all calves born represents a significant opportunity for the New Zealand dairy industry to control BVD voluntarily. This coupled with a collective' willingness to test all calves to identify PI animals, and remove them from farms, alongside good biosecurity, will deliver economic benefits for every farmer in New Zealand and lead to significant improvements in New Zealand's BVD status.
To motivate change, it's crucial we all get on board with a determined community effort that encourages all farmers to get on board for the benefit of their farms, the community, the region and the country.
Ask your neighbour if they know the BVD status of their calves.
DairyNZ. BVD Virus.
Han JH, Weir AM, Weston JF, Heuer C, Gates MC. Elimination of bovine viral diarrhoea virus in New Zealand: A review of research progress and future directions. New Zealand Veterinary Journal 66(6), 273–80, DOI: 10.1080/00480169.2018.1509030, 2018
Hill FI, Reichel MP, McCoy RJ, Tisdall DJ. Evaluation of two commercial enzyme-linked immunosorbent assays for detection of bovine viral diarrhoea virus in serum and skin biopsies of cattle. New Zealand Veterinary Journal 55, 45–8, 2007
Reichel M, Lanyon SR, Hill FI. Perspectives on Current Challenges and Opportunities for Bovine Viral Diarrhoea Virus Eradication in Australia and New Zealand. Pathogens 7(1), E14, 2018