BVD is a viral disease of cattle mainly presenting with a variety of reproductive problems. Current estimates are that it costs the UK between £50m - £75m. These costs are a combination of the reproductive problems (stillbirth, mummification, embryonic death, infertility), ill-thrift in growing cattle, pneumonia and scour in calves as well as increased susceptibility to other conditions. The wide range of clinical signs can mean that BVD does not always present in the same way on each farm it infects.
The most important method of spread is by the creation of Persistently Infected (PI) animals. A calf inside an unvaccinated cow, exposed to BVD virus during the first 4 months of gestation will be infected without mounting an immune response. In this case, the virus grows within the calf unhindered and is shed constantly. This is a great danger to other animals in the herd. These PI animals must be found and removed from the herd urgently.
BVD virus can also be spread by nose-to-nose contact or by semen from infected bulls.
Currently, the risk of unknown BVD virus entering or being present in English herds is high, so we recommend protecting all breeding animals with vaccination. We have a couple of different vaccines which protect naive cows from infection with BVD virus, and protect their unborn calf from becoming a PI. These vaccines are very good. The protection must be in place before the heifer or cow is served to ensure that the unborn calf is protected from conception.
But vaccinating does not give you 100% safety - PI animals will not be affected by vaccination and will always give birth to PI calves. Also, a very high infection pressure from very close contact with one or more PIs can overwhelm the protection from vaccination. It is vital to know whether you have one or more PIs in your herd, because blindly vaccinating if there are PIs present is not maximising the value from your vaccine purchase. This is one of the ways that BVD Stamp It Out can help - contact us to get involved.
We are often asked whether we would stop vaccinating in herds which are tested negative. The answer to this is currently 'No', as the risk of virus entering the herd remains high until such time as BVD is eradicated from England. With a national effort, such as the BVDFree England campaign, especially in conjunction with the RDPE-funded BVD Stamp It Out initiative, we have a serious chance of eradicating BVD from England, just like the Scottish have through their national campaign. If England were to become BVD free, it may well be possible to stop vaccinating in certain herds.