Guidance for veterinary surgeons: bovine viral diarrhoea (BVD) eradication

Following the Gwaredu BVD scheme, which successfully screened more than 80% of the cattle herds in Wales, Welsh Government was approached by industry with a request for legislation to support BVD eradication.

Whilst Gwaredu BVD achieved fantastic results in its coverage of cattle herds, disappointingly only 50% of persistently infected (PI) animals were culled or sent to slaughter and around 25% of the PI animals identified during the programme were sold on to other keepers. The industry recognised that, without legislation, eradicating BVD would not be possible.

Welsh Government’s approach to BVD eradication involves partnership working with an industry Steering Group, representing farming unions, veterinary delivery partners (VDPs) and other organisations such as Welsh Lamb and Beef Producers, Hybu Cig Cymru and the Livestock Auctioneers Association. The Steering Group sets the broad strategic direction for BVD eradication and advises government on the requirements for and the implementation of legislation. A BVD Technical Advisory Group provides support and advice to both the Steering Group and Welsh Government.

The BVD legislation follows the familiar approach of Gwaredu BVD. Youngstock management groups within the herd are identified and from these a small number of animals are sampled for antibodies, which could indicate viral exposure. 

Using this methodology over 80% of the herds within the Gwaredu BVD scheme were identified as being free from BVD.

Herds are given a status based on the presence or absence of antibodies in the annual screen. If all samples are BVD antibody negative, then the herd will have a negative status which lasts for 12 months. Any seropositive animals mean the herd will receive a not-negative status. 

The legislation requires every holding with cattle in Wales to complete an antibody screen at least every 12 months. Any herds which do not complete the screen will be assigned a not-negative status.

This guidance should be read in conjunction with the screening guidance already issued by BVDCymru. 

A negative herd can continue to trade cattle without restriction and without the need to carry out a BVD pre-movement antigen test. A negative holding should take steps to prevent BVD infection entering their herd. It should be noted that if animals are bought from outside Wales, they will need an individual status – see later sections. 

If a herd has a not-negative status due to a positive test in the annual screen, further testing requirements will apply. 

If you believe the status of not-negative is inappropriate, please see the later section on changing status.

If the status is appropriate, then the following must be carried out:

• every individual animal will require an individual antigen status. This testing can be either blood or tissue based, and tissue tagging can be performed by livestock keepers
• all calves born into herds which have shown evidence of exposure to BVD virus at their annual screen will require testing before they exceed 20 days of age with an official ear tag sample
• the tagging and testing of newborn calves must continue until at least 12 months after the herd regains its negative status

If this process leads to a virus positive animal being found, then the holding status will remain not-negative until the animal is shown to be negative or removed from the herd. 

Keepers with negative status holdings can move their animals as usual with no further BVD testing requirements.

Keepers with a not-negative holding status may continue to move animals off their holding, however they will require a valid negative pre-movement antigen test done by a vet or an approved blood sampler or ATT.  Not-negative farms can still receive animals, but they must comply with the movement legislation as for other farms.

Pre-movement tests are antigen tests and are valid for 60 days from the date of sampling. Pre-movement tests can be blood or tissue based. Pre-movement tests must be performed by a vet or person under the direction of a vet (employed by or reporting to the vet). There is an exception for young calves, aged 20 days or less, which may be sampled by the keeper with a tissue tag that is also an official ID ear tag. A negative result using this process would also be considered a valid pre-movement test.

Where an animal is moving holdings, the current keeper of the animal must inform the receiving keeper of the pre-movement test results (antigen test results). In any and all cases, keepers must not move a virus positive animal. 

The BVDCymru system will inform farmers of their herd status, any pre-movement test requirements that may apply to their animals, and keep track of the validity of a pre-movement test.

Animals within Wales can only move if they are coming from a negative holding or have a valid BVD antigen pre-movement test from a not-negative holding.

These requirements apply whenever animals move between different CPHs, regardless of whether ownership changes.

If non-compliant animals are moved onto a holding the BVD system will detect these moves and advise the receiving keeper.

Moving non-compliant animals onto a negative holding puts that herd status at risk and is in breach of the legislation. 

Animals moving onto a Welsh holding from outside of Wales, and which do not have a known status, will have 20 days to get their status added to the BVDCymru database, either through evidence presented by the new keeper or by testing the animal for antigen. 

At present no individual BVD statuses can be automatically recognised for cattle moving into Wales, unless those animals have previously been antigen tested while on a Welsh holding. 

Veterinary surgeons can update individual animal statuses should they be provided with evidence of a previous negative BVD antigen test, which would remove the requirement to post-movement test (see guidance later).

There are several types of BVD test recognised within the legislation:

*with appropriate training.

If you have clients who already tag and test their calves, they should be encouraged to continue this approach. If BVD enters a herd, tagging and testing provides keepers with an opportunity to identify and remove PI animals early after their birth.

Furthermore, anticipated changes to the BVD legislation will recognise individual animal antigen results as contributing to the overall herd status. This development is based upon feedback from the veterinary profession, farming industry and the BVD Steering Group. Animals having an individual negative BVD status will therefore provide greater flexibility for herds to achieve their BVD negative status in future.

An individual negative status will follow the animal throughout its life onto new holdings, which may be a desirable feature for marketing or trade.

You can change the status of a holding by making a declaration on the BVDCymru system. To do this you must have supporting evidence for the change of status and be prepared to provide this evidence if requested. Further guidance is provided later in this document.

You can change the status of individual animals on the BVDCymru system if you have evidence to support this change. You should retain records of this evidence.

You may be requested by clients to change the status of animals, which they have purchased from outside of Wales. This is acceptable and further guidance is provided under “Evidence required to change BVD statuses”.

The legislation provides scope for you as a veterinary surgeon to decide, based on your own professional judgement, what constitutes an appropriate sample of the available livestock. The screening requirement applies to every holding and is not optional. You may need to consider the use of vaccination on farm in the interpretation of results. To avoid future false positive results, it may be worth considering alternative vaccination strategies with your client.

Furthermore, anticipated changes to the BVD legislation will recognise individual animal antigen results as contributing to the overall herd status.

Inconclusive antibody results are not currently captured by the BVDCymru system, these results may be reported online as insufficient samples. In instances where a definitive result has not been obtained, the sampling should be repeated.

Inconclusive antigen results are not currently captured by the BVDCymru system, these results may be reported online as insufficient samples. In instances where a definitive result has not been obtained, the sampling should be repeated. If an ear tag test has not yielded a definitive result, the repeat testing should use a sample of blood to avoid applying excessive ear tags to an individual animal.

The legislation provides veterinary surgeons with the ability to change the BVD status of herds and individual animals. The Scottish BVD legislation also provides scope to change herd status, however it is rarely used.

The consequences of erroneously changing a BVD status from not-negative to negative could be severe should PI or positive animals subsequently be sold to other keepers.

The BVD Technical Advisory Group has considered the circumstances in which such changes could be justified. It also endorsed guidance on the evidence that should be collected to support these decisions.

Herd status 

Unknown to negative 

• antibody screen with all animals being negative for BVD antibodies
• all animals on farm have a virus test that is negative 

Not-negative to negative 

• antibody screen with all animals being negative for BVD antibodies 
  • Where possible it should also include the animals that tested negative in first instance and be at least 28 days after the initial test. See Screening guidance issued Autumn 2024
• all animals on farm have a virus test result that is negative on the BVDCymru system.  It is advised to undertake a check against CTS records in this scenario
• a CHeCS accreditation certificate where the screening method is calf screening

Individual animal status 

Positive to negative 

• a laboratory report (headed) with a veterinary signature showing a virus test that includes the official ID of the animal and the negative result details

Unknown to negative 

• a laboratory report (headed) with a veterinary signature showing a virus test that includes the official ID of the animal and the negative result details

Persistently infected animal 

• any animal with a double positive antigen result cannot have its status changed

Serious consideration should be given to any decision to change status. Veterinary surgeons must ensure they maintain evidence should their decisions and any related consequences be challenged.

For queries regarding how to change status contact the EID Cymru Service desk. For any additional support and advice contact BVDCymru.

Welsh Government is working in partnership with the BVDCymru Steering Group and the Technical Advisory Group to ensure that the BVD eradication process works for cattle keepers and vets in Wales. We recognise the legislation will need to evolve and adapt over time. Additionally, it is important that legislation in Wales does not unduly conflict with legislation either in place or being developed in other UK nations. 

Based upon industry feedback and advice, Welsh Government is proactively reviewing the legislation and considering whether amendments could be made in future to support alternative screening methods for herds, including reducing the sampling burden in PI hunts. 

Any potential changes to the legislation will be pro-actively communicated as they develop and come into force. Until any forthcoming amendments come into force, the current legislative requirements apply and must be observed.