He says the many gains would include improved fertility and consequently less unplanned culling, better growth rates and feed conversion performance, and reduced medication costs.

Mr Miller recommends a three-part process suitable to all types of cattle enterprise to maximise the “eradication dividend” and minimise the risks posed by BVDv and other infectious diseases: “First, know your own herd’s disease status and take advice from your vet about any changes for the better that could be made,” he says.

“Then, before any new cattle arrive on farm, establish their health status and minimise the infectious disease risk to animals already on the unit and new arrivals alike. Finally, develop an ongoing disease management policy for your farm and make sure it is working 365 days a year. Routine vaccination for BVDv may play a part in steps two and three in many regions.”

As BVDv eradication in Scotland proceeds, Mr Miller acknowledges that open borders mean constant vigilance will be needed to preserve the progress made. He cautions that without widespread adoption of whole herd health protection, the BVDv eradication dividend could be squandered.

“Already from BVDv-free Scottish herds, we have fantastic opportunities to maximise performance potential,” he adds. “But we must also recognise that non-exposure to infection makes cattle vulnerable when they move to a new unit and mix with cattle from different sources. This is particularly so during the early and mid stages of the eradication process, when it is inevitable that undetected BVDv-PI [persistently infected] cattle will still be present among the population.

“The reality is that many farmers who operate feeding enterprises already manage the risks of mixed sourcing. One of our challenges is to make this risk management easier on Scottish units and, as we move towards wider control and eventual eradication of BVDv, we must not ignore lessons learnt. Even when eradication has been achieved, strategic use of vaccines to protect cattle at risk will remain an important part of whole herd health protection for as long as there are open borders to cattle movements.”

Livestock vet Robert Anderson from the Merlin practice in Kelso favours an integrated approach involving the entire breeding and feeding production chain. “If breeders can test calves for BVDv at six months of age before they’re sold, they might as well do it at one week of age instead using an ear notch from the secondary tag,” he suggests.

“If the calf is a PI, you can get rid of it before any further rearing costs have been incurred. And if it’s BVD-negative, then the dam is too, so you’re getting two test results for the price of one."

“With test results on file, breeders can state with confidence that calves they’re selling are not PIs, and even pass on a copy of test results to the buyer with the passport. If calves have also had a pre-sale vaccine with a BVDv component, that can be declared too. By taking such action, breeders introduce valuable reassurance about health status to the buyer of their calves. Indeed, without testing to eliminate PIs plus routine vaccination, any control plan will fail.”

In the absence of specific confirmation of calves’ health status, Mr Anderson suggests that the safest option is the time-tested adage, ‘let the buyer beware’. He advises a simple blood test and appropriate vaccination on arrival, and keeping newly purchased cattle segregated until test results are known. He adds that this is equally valid for arrivals to fattening units or breeding herds.

Introducing BVD virus to an unexposed breeding herd can have huge repercussions, according to Pfizer vet William Sherrard. “Depending on the stage of pregnancy at the time of infection, foetuses may abort or be born with deformities,” he explains. “But they may also be born alive and apparently normal, while actually carrying and spreading the virus continuously. This is what’s called persistently infected or PI status."

“When a BVDv-PI animal is mixed with previously unexposed and unvaccinated cattle, the virus’s immunosuppressive effect makes infected animals much more vulnerable to other diseases such as pneumonia. Clearly, this can cause major losses on a beef finishing enterprise.”

To defend against this, Mr Sherrard recommends in order of preference:

• Purchasing cattle which are known to be BVDv accredited free, or which have already been screened to detect and remove PI animals, and vaccinated for BVDv.
• Screening animals on arrival to detect PI animals, either by blood sampling or ear notching, and taking veterinary advice about the best course of action based on test results.
• Purchasing cattle already vaccinated for BVDv. While this does not rule out the risk of buying in a PI animal, it does ensure that vaccinated cattle have some protection in place should they be exposed to infection.

As well as the threat of BVDv, the risk from other viruses, particularly those associated with bovine respiratory disease, needs to be taken into account when buying in stock. “New arrivals to finishing units should be vaccinated against IBR as a bare minimum,” adds Mr Sherrard.

“Also, depending on the age of those cattle, your vet may advise including vaccination against the two commonly occurring pneumonia viruses, RSV and PI3. Cattle sold under the SureCalf® programme are vaccinated pre-sale against these three viruses and BVDv, ahead of the stress associated with weaning, transport, re-housing, and mixing with new group-mates, meaning the vaccine is working and minimising disease threat during this high risk period."

“Among all options, the safest is to purchase animals from a herd free of the BVD virus that have already been vaccinated for BVDv and the viruses commonly associated with respiratory disease.”