FOUR years on since testing for Bovine Viral Diarrhoea (BVD) became mandatory in Scotland's breeding cattle herds the number of incidents of BVD infection and indeed positive herds is well and truly on the wane.

The virus, which causes a complex range of diseases resulting in poor reproductive performance, with more barren cows; abortions and the birth of deformed calves or calves with increased susceptibility to other infectious disease, can have huge repercussions in both beef and dairy herds. Introduction of the disease to herds for the first time can have devastating effects on the health of young calves, with a significant increase in treatments for disease and reduced survival.

Not surprisingly, it carries a big financial burden, with figures from the Scottish Government quoting annual benefits after eradication of the BVD virus of up £15,800 in dairy herds; £2400 in in beef herds per 100 cows.

That's the bad news. The good news is, 89.6% of breeding holdings in Scotland now boast a negative BVD status.

"Our BVD control programme is creating real benefits for the vast majority of our herds and the push is now on to finish the job and make Scotland the first country free of BVD within the British Isles," said George Caldow, of SAC Consulting Veterinary Services.

Since the mandatory scheme to eradicate the disease was introduced in February 2013, up until the end of January 2017, some 4188 Persistently Infected calves, known as PIs – cattle that are born with the virus and which shed the virus continuously – have been identified.

Thankfully, the vast majority of these have been culled, but of those PIs more recently born, some 410 remain on 167 holdings in Scotland. That might sound a lot but the 10.4% of infected herds are mostly confined to dairy units in the South-west and the figure is falling.

The birth of PIs, which are the cause of the vast majority of new BVD infections, means that the disease cannot be eradicated overnight.

In most cases, it takes a full year to re-establish a herd’s negative BVD status after removal of a PI as you have to wait for all the heifers and cows that were pregnant while the PI was alive on the farm to calve, and then test the calves for BVD virus. Only when all these results come back as BVD negative, can the herd status be declared to be negative.

This 12-month delay for return to negative status is another reason to remove the PI as soon as possible: the sooner it is gone from the herd, the sooner you can get your BVD negative status back and the sooner all cattle from the herd can be sold freely through the live market again. And of course removing these animals safeguards the health of your cattle and those of your neighbours. Indeed consideration of the risk of BVD virus coming into the herd is important. In the past it has mostly come in with a PI animal or female carrying a PI calf, but now when the overall risk is much lower the spread through over the fence contact with other cattle or on the clothes and equipment of visitors to your herd is relatively more important.

Compulsory annual testing is in place to support the programme and to facilitate safe trade. And there is a range of testing options to suit the individual herd situation. Consult your vet to get the best fit for your herd and to ensure that both vaccination and biosecurity for BVD is part of your health plan.