Guidance for Farmers: complying with bovine viral diarrhoea legislation in Wales

Bovine Viral Diarrhoea (BVD) is a disease of cattle which has major impacts on the health, welfare and productivity of affected animals. Following the Gwaredu BVD programme, which saw over 80% of Welsh cattle herds screened for BVD, the Welsh Government launched a consultation on the introduction of legislation to control and eradicate BVD in Wales.

The aim of the BVD legislation is to ultimately eradicate BVD from Wales. BVD is a disease which we can realistically eradicate, as has been demonstrated in several other European countries.

There are multiple approaches that can be applied to BVD eradication on a national level. The approach currently being used in Wales is the “check test” serological screening of groups of different management groups within herds, to find evidence of disease exposure. This is the approach used in Gwaredu BVD and is also the model used by Scandinavian countries to eradicate BVD.

The check test method is a sensitive way of identifying BVD infection at a herd level, while also keeping the number of mandatory samples that are taken to a minimum. This means that herds without evidence of BVD exposure need not incur excessive financial cost.

Once herd level infection is detected, there will be a requirement to follow-up test to identify any persistently infected (PI) animals on farm. PI animals are made when animals at a certain stage of pregnancy become infected, the calf is born infected and carries the virus for life, shedding and spreading the virus. PI animals are the main risk for onward BVD spread.

There are two types of test we recognise for BVD within the Wales BVD Order.

Antibody tests

Antibody tests check for exposure to the virus. Antibody responses can also be found because of BVD vaccination. For this reason antibody tests will primarily be targeted at young unvaccinated animals. 

An antibody response in an unvaccinated animal indicates the animal has been infected with the virus and has now mounted an immune response. This animal is healthy, but the test has shown us that virus has been, and could still be, circulating in the herd.

Antibody tests are performed on blood samples taken by your own vet, or a trained and approved member of their staff.

Antigen tests

Antigen tests check for the virus itself. Antigen tests can identify if an individual is infected at the moment in time when the sample is taken. 

Antigen tests can be performed on blood samples or tissue samples collected through specific ear tags.

A positive result on an antigen test could indicate that an animal is either a PI, or that they have a temporary, transient infection that they will clear in a few weeks. 

After a positive antigen test it is critical to retest the animal.

All cattle herds in Wales must undertake a mandatory annual BVD screen. This screen is the check test, and will be used to determine herd status.

The check test screens five animals from separate management groups. This test is looking for antibodies which indicate exposure to infection and that the virus could be circulating in the herd.

Your vet will help select the animals for a check test. 

The annual antibody check test should use method (a) below. Where this is not possible method (b) should be used. When method (b) is not possible method (c) should be used. Finally if no other method is appropriate method (d) should be used.

1. Five unvaccinated calves aged 9 to 18 months

Your veterinary surgeon should take samples of blood from five unvaccinated calves in the age range of 9 to 18 months in each relevant  separately managed group (groups between which in the vet’s clinical judgement there is no appreciable risk of direct disease spread). Ten unvaccinated calves aged 0 - 9 months

If any of your sample of calves are aged 0-9 months, then your veterinary surgeon should take a sample of blood from not less than ten unvaccinated calves in the age range 0-9 months in each separately managed group (as above). 

2. If you have no animals that fulfil the above criteria then your veterinary surgeon should advise on an appropriate sample population and size from the available age ranges within the herd.

Each cattle holding in Wales will have a herd level status following a test:

• Unknown - no annual screen has taken place yet. This status is time limited and predominantly applies to new herds within their first 30 days.
• Negative - there is no evidence of BVD infection or exposure
• Not negative - there is evidence of BVD infection or exposure or mandatory herd screening has not taken place within compliance deadlines.

Individual animals are also assigned a status based upon antigen tests. 

• Unknown:  these animals have not had an antigen test so their status is unknown.
• Negative: these animals have had a negative antigen test. This status lasts for life.
• Positive: these animals have had a positive antigen test, they should be re-tested at least 3 weeks later to determine whether they are persistently infected.
• PI: these animals have had repeated positive antigen tests. These animals should be culled. If you choose not to cull them then they must be isolated for life and can only leave your holding to slaughter.

If all your antibody screening results are all negative then your herd will be given a negative status.

This means no evidence of infection has been found in your herd. Your herd can continue to trade as normal for the next year. You should take care not to introduce BVD into your herd, and for further advice consider consulting your private vet.

You should ensure that you only introduce animals from other negative holdings, or animals with a negative pre-movement test.

If you buy cattle from English or Scottish herds you should seek assurance that the animals are free from BVD. You will be required to post-movement test the animals, and if they have a positive post-movement test then you will lose your negative status.

Any positive result on your annual antibody screen will result in a not negative status. Positive antibody results can indicate exposure to virus, and means there is a risk that virus is circulating in the herd.

If you have not completed an annual antibody screen in the past 12 months your status will also be set to not negative. If you decide to complete your annual screen and all the results are antibody negative, then the herd status will become negative.

When a herd has an animal with an individual status of antigen positive, or a PI animal in it, then the herd will have a status of not negative.

If you have bought an animal from a BVD not negative holding in Wales, which has not had a valid pre-movement test, your status will be set to not negative.

If a herd has bought an animal from a holding outside of Wales and the animal has not been post-movement tested within 20 days of arrival, the holding status will become not negative. If the post-movement test result is positive the holding will also become not negative.

If you have a not negative status you face movement restrictions and further testing requirements from 1 July 2026.

You may:

• send animals to slaughter
• move animals to a veterinary practice for treatment
• move cattle onto the holding

You must:

• arrange for the sampling of all animals on farm to give them an individual BVD status based upon an antigen test
• test all newborn calves on your holding using ear tissue tagging. This requirement will remain in place for 12 months after you regain negative status and includes aborted or stillborn calves
• any antigen positive animals should be retested no less than 21 days after their positive test to determine PI status
• if any PI animals are identified on your holding they must be isolated for life and can never move to another holding

You must not:

• move any cattle off holding without a valid pre-movement test
• move any PI animal off the holding unless to slaughter

If you have had a positive antibody result at your annual screen, your status will be not negative. This means that you will need to:

• undertake a screen of all cattle in your herd to identify any PI animals. This will mean every animal needs an antigen test and can be either an ear tissue tag, or your veterinary surgeon can arrange collection of a blood sample
• you will need a pre-movement test to move animals off your holding. This must be an antigen test. A pre-movement test needs to be performed by your vet and will be valid for 60 days
• test all newborn calves in your herd while your status is not negative, and for a further 12 months after you regain negative status

Any animals which have two positive antigen results will be given PI status. These animals can never be moved to another holding. You should cull them. If you decide to retain PI animals then they must be isolated for life. 

PI animals may be sent to slaughter.

To move from not negative to negative status you will need to evidence that there are no positive or persistently infected animals on your holding. This means testing every animal for antigen to assign them an individual animal status.

When every individual animal on your farm has a negative status then your herd status will be changed to negative. However, you will have the continued requirement for 12 months of screening all newborn, aborted or still-born calves.

Negative herd status

If your herd has a negative status there are no specific requirements around calf sampling, you may wish to test calves for your own assurance. If you currently screen calves as a part of your routine farm health management you may wish to continue doing so, doing so will provide your animals with individual BVD statuses should you have any issues in the future. 

Not negative herd status

If your herd status is not negative or your herd has had a not negative status within the previous 12 months then you must screen all calves born into your herd within 20 days of birth. This must be done with an ear tissue tag sample.

This means that even if you have completed a PI hunt and regained negative status, you must continue testing newborn calves for 12 months from the last date of your not negative status.

This requirement also applies to any aborted or stillborn calves, which must be tagged within 7 days.

Negative herd status

If your BVD status is negative then you can move and sell your cattle as you normally would.

Not negative herd status

If your  BVD status is not-negative then you cannot move stock from the holding without a valid pre-movement test. This includes selling stock or moving cattle to any other holding you own, manage or graze.

Pre-movement tests must be taken by a veterinary surgeon or approved blood sampler, and are valid for 60 days from the date of sampling. You must inform the new keeper of the animal of the BVD pre-movement test result no more than 3 days before moving the animal.

No animal with an individual BVD status of positive or PI is permitted to move.

Movements to slaughter may continue as normal for all herds regardless of BVD status, you may also move animals to a veterinary practice for treatment as required regardless of your BVD status.

All cattle holdings within Wales will have a BVD status. If you are moving cattle on from a negative herd in Wales there will be no implications for you and you may continue as normal.

If you are receiving cattle from a holding with a not negative status after 1 July 2026 they should have had a negative pre-movement test within the previous 60 days. 

If this condition has been followed then there will be no implications for you, but you should request evidence of a negative pre-movement test result for your own assurance.

After 1 July 2026, if you receive cattle from a holding in Wales with a not negative status which do not have a valid pre-movement test then you risk losing your negative status. 

If you have two or more separate holdings each will need their own BVD statuses. The rules for moving animals between your own separate holdings are the same for movements between any other holdings.

Movements can be made freely from a negative holding to any other holdings.

Movements from holdings with unknown or not-negative status require a negative pre-movement test.

These requirements exist to keep your negative holding safe, and ensure that it remains negative.

If you move cattle onto your holding from outside of Wales which do not have a known individual BVD status then you will be required to arrange for a post-movement antigen test within 20 days of the move. This test must be taken by a veterinary surgeon or approved blood sampler. 

If a post-movement test result is positive then your herd status will change to not-negative, see “Implications of a not negative status” above.

Keepers moving in-calf cattle with unknown individual BVD statuses must isolate them until they calve or until a negative post-movement test has been performed. Be aware that the calf may have a different status to the dam, so you should also test the calf once it is born. Beware of Trojan calves, these pose a real threat of introducing BVD to your herd.

A note on BVD statuses of cattle moving from outside Wales

At present only cattle which are sampled in Wales or have a result submitted onto the Welsh BVD system will have a known BVD status. All others will have an unknown status. If stock you purchase has been previously screened for BVD antigen and has negative results, you should ask the vendor for a copy of these. If you provide these to your vet they are able to change animal statuses and a post-movement test will not be necessary.

Antibody test

Antibody tests are tests for evidence of immunological responses. These tests are performed on blood samples and can detect responses to either infection, providing evidence that animals have been exposed to the virus. Vaccination can also trigger positive antibody results so selecting the right animals for these tests is critical.

Antigen test

Antigen tests detect the virus itself in a sample. They provide evidence that an individual animal is infected with the virus at the time which the sample was taken.

Approved blood sampler

An approved blood sampler is a person authorised by authorities to collect blood samples from cattle to support the control of BVD. These persons can only sample under the direction of a veterinary surgeon, so will be employed within veterinary practices.

Bovine Viral Diarrhoea/BVD

This is a viral disease of cattle. Despite the name the virus does not commonly cause diarrhoea, however it is immunosuppressive making cattle more susceptible to other diseases such as respiratory or enteric infections, and causes reproductive losses.

Check test

A way of sampling for herd level BVD status with a relatively small sample size using antibody status of small numbers of unvaccinated animals. This keeps the mandatory cost to keepers associated with BVD screening to a minimum.

Ear tissue tag

These are ear tags which collect a sample of tissue when they are applied. This tissue can then be tested for antigen to determine individual BVD status of an animal.

Persistently infected (PI) animal

These are animals which are permanently infected with BVD virus. These animals were infected before they were born within the uterus of their dam. Their immune system has developed alongside the virus and as a result they do not recognise BVD virus as an infection. They will shed large quantities of virus into their environments and pose a major risk of infecting other animals.