The launch of a Scottish BVD eradication scheme last December has put the subject firmly in the spotlight for dairy and beef farmers in the rest of the UK, writes Thomas Tiley, vet adviser for Novartis Animal Health, a joint sponsor of two BVD control programmes in England.
By December 2012, all Scottish herds will be required to have been screened for the virus, with results passed to the Scottish Government. After this date, the Scottish Government plans to make it an offence to knowingly sell a persistently infected (PI) animal, which has implications for English farmers who sell stock in Scotland.
Not that BVD has been off the agenda in the rest of the UK. Back in 2006, Joe Brownlie and Richard Booth, of the Royal Veterinary College, established a pilot eradication scheme in south-west England, with the preliminary finding recently published in the Veterinary Record.
One of the main conclusions of the study, which involved 30 dairy herds and four beef herds, has been that BVD eradication is a real possibility even in areas where biosecurity was more difficult to maintain. An earlier eradication plan in Orkney had the advantage of the islands’ natural biosecurity, but there was no way of knowing how this would play out in more open areas.
The other, and equally important, aspect of the scheme is the ongoing gathering of data to show if BVD-free herds have a generally higher standard of herd health and fertility, and what the financial implications are for farmers who decide to take part. Mr Brownlie and Mr Booth intend to publish on this later in the year, and it is anticipated the financial arguments in favour of eradication will be powerful.
There are other projects under way in the UK. In the north of England there is one at Coquet Valley in Northumberland involving 30 farms and one at Nidderdale in North Yorkshire that has 20 farms on board. Both sites have been chosen with biosecurity in mind, using natural features of the landscape, such as hills and rivers.
The first stage of any eradication or control project is to find out what the farmer wants, and what they are prepared to do to achieve this. A full biosecurity audit should be performed at this stage to ascertain and minimise the risks of BVD entry into a herd. Simple and relatively cheap test are available to determine the BVD status of a herd. Bulk milk tests and blood samples from five to 10 youngstock in each management group above six month will allow your vet to determine whether or not the virus is likely to be present in a herd.
If the herd is clear, then a decision needs to be made on what action, if any, should be taken. Depending on biosecurity or the frequency of incoming stock, the farmer should vaccinate to help maintain BVD-free status. He would certainly be advised at this stage to develop a surveillance programme with his vet to continually monitor the herd, enabling rapid detection of any disease incursion.
For herds where the virus is present, it is recommended that PI animals are identified and culled. These animals are thought to make up 1-2% of an infected population and act as a reservoir for the disease. They tend to be sickly and are a real risk to the rest of the herd. They maintain the disease within the herd and are a major cause of immunosuppression and poor fertility in the animals they infect. In some cases, they can appear normal and survive to produce more PI offspring. Removing PI animals and herd vaccination provides the quickest route to BVD freedom for infected herds.
From a biosecurity viewpoint, eradication by geographical area rather than individual farms is easier, but the group projects and schemes under way in the UK shouldn’t eclipse the hard work being done by individual vets and their clients on the local level. This is undocumented at this stage but will no doubt be a significant factor in achieving a highly beneficial goal for dairy and beef farmers: a BVD virus-free UK.