By Nigel Miller, Chairman of Livestock Health Scotland

"BOVINE VIRAL Diarrhoea (BVD), which erodes health and production within affected herds, is a resilient virus, infecting calves in the womb, creating a new generation of virus super-shedders. These persistently infected (PIs) animals are the driving force of the disease, continually shedding high levels of virus, spreading infection within the herd and seeding new infections.

Detecting PI cattle and removing them from the herd is the key to eradication.

The Scottish BVD Eradication programme created a national framework to identify risk herds and incentivise the detection and removal of PIs. The faster that process moves, the faster herds become free of the virus and the lower the risk of spread.

We are entering the toughest stage of BVD eradication in Scotland with now less than one in 10 herds affected in many regions, but PI calves are still being born and can quickly spread infection. To maintain the momentum of eradication BVD, PIs must be identified promptly and culled as quickly as possible. Tissue tag testing aids early detection and is an effective way of screening calves born to animals purchased in calf.

With spring turn out, and the bulling period approaching this is a crucial moment. It is vital to remove PI calves before the bulls start working to break the disease cycle and avoid a new generation of PI calves being born next year. It is important to ensure PI cattle do not go to grazing and pose a risk to all contact cattle, including neighbouring stock. Unless we get this right BVD will continue to fight back.

BVD is probably the number one production disease and eradication can be challenging in some herds especially when linked to complex management systems. If eradication has not progressed well it is worth reviewing the testing approach with your vet, to ensure no PIs remain undetected, and that the risks linked to grazing away from home and bringing in new cattle are properly managed.

Phase 5 of the BVD scheme is now being developed, with guidance from the BVD Advisory Group. The aim will be to get tough on PI cattle and through more robust controls protect herds which are free of BVD virus.

Scottish Government has already added a new status to the BVD herd classification system, high risk herds that have retained PI cattle on the holding will now be classified as ‘positive herds’.

This is a start of a tougher approach moving a heavier burden of control onto the herds which don’t actively drive BVD eradication and represent a risk to the health status of neighbouring stock. Those herds which slip into positive herd status can regain not-negative status by removing the BVD PI animals.

It is critical that we move eradication on quickly, being tough on BVD PIs is essential for us all."

(This blog originally appeared on