Recent test results have proven a significant change in the patterns of bovine viral diarrhoea (BVD), according to Animal Health and Welfare Northern Ireland (AHWNI).

The infection is currently quite prominent in the Armagh and Newry Divisional Veterinary Offices (DVO) areas.

The infection has been recorded in all herd types in the areas, and is now has the equivalent of one third of the total number of herds in Northern Ireland affected by BVD in the last year.

AHWNI said "Geographical hotspots have been a persistent feature of the BVD problem here and farmers are advised to take steps to protect their herds."

BVD is a viral disease of cattle, mainly spreading through herds via persistently infected (PI) calves.

PI calves are animals whose mother was exposed to the virus during her second to fourth month of pregnancy, or was a PI animal herself.

If a calf is exposed to BVD, it will express clinical signs of infection such as: reproductive problems; a fatal condition called mucosal disease; and weakening of the immune system, leaving cattle more susceptible to other infections such as scour and pneumonia.

The majority of PI cattle die before two years-of-age, either from mucosal disease or other illnesses.

PI animals need to be culled from the herd, therefore all calves should be tested using ear punch samples when tagging.

According to AHWNI, there have been approximately 500 herds across Northern Ireland with at least one BVD positive result in the last year.

The animal health organisation said that Armagh is the area with highest percentage of affected herds, while Newtownards had the lowest.

However, AHWNI said that the impact of herd restrictions for BVD is clear, as at the start of September, there were nine BVD positive cattle in six herds being retained for more than 28 days.

This is a large contrast to the same time in 2024 when there was 29 cattle being retained in 25 herds.

AHWNI warned farmers that they should remain vigilant despite decreasing herd incidence of the infection.

Farmers can try to prevent the spread of the infection by improving neighbouring livestock boundaries, limiting contact through the use of either electric or double fences.

Neighbouring farms can also coordinate, managing their season to ensure their cattle are not 'sharing a ditch'.

Farmers should be following their animal health plans by sticking to a strict vaccination programme for the infection, especially if their herd is at high risk.

Farmers should try and maintain a closed herd. If buying stock in, ensure they have tested negative for the infection, and always maintain a quarantine system (ideally four weeks).

AHWNI stated that there continues to be cases of BVD developing in herds that have not previously been a BVD positive herd.

For this reason, it is important for farmers in BVD-free farms to still regularly test their animals to ensure their herd has been not infected, and get ahead of the infection early if it has.

However if an animal tests positive for BVD and the infection is still present after the seven-day grace period, DAERA will restrict the herd and any herds in contact for a minimum of three weeks.

To be unrestricted, a herd must be BVD-negative at least three weeks after culling the positive, and any newborn calves must be over 30 days-of-age and testing negative for the infection.