Bovine viral diarrhoea (BVD)

What are the clinical signs of the disease?

BVD virus affects cattle of all ages, but clinical signs of infection are most common in young cattle (aged 6–24 months).

Clinical signs include:

• Reduced immunity leading to secondary infections
• Fever
• Lethargy or depression
• Diarrhoea
• Reduced productivity, e.g milk yield
• Reduced fertility
• Abortion
• Weak and premature calves
• Birth defects, particularly to eyes and nervous system
• Death

There is no cure for BVD. Treatment consists of supportive care for secondary infections.

What is the impact of the infection?

BVD has been estimated to cost between £13 and £31 per cow per year in Great Britain.

The national cost could be as high as £61m per year (Bennett and Ijpelaar, 2005).

How is BVD transmitted and spread?

BVD virus is largely spread from contact with infected animals.

The virus is spread via:

• Nasal discharge
• Saliva
• Semen
• Urine
• Faeces

Adult cattle infected with the virus usually recover and become immune. However, if a cow is infected with the virus during early pregnancy, her calf will become persistently (permanently) infected.

These persistently infected (PI) calves act as 'super spreaders' of the disease, producing large volumes of virus throughout their lives. They become a reservoir and the main source of infection for the herd (and any in-contact cattle).

Identifying PIs is critical to enabling management of the disease and in helping to eradicate BVD.

Although they may appear entirely normal, persistently infected calves are usually:

• Smaller
• Suffer from recurring illnesses
• May be born with defects, e.g. blindness/lack coordination

These animals should be culled to prevent infection and for welfare purposes.

What can I do to prevent and control BVD?

Prevention and control of BVD can be achieved through:

• Herd biosecurity – to prevent the disease entering the herd
• Vaccination – to ensure immunity and prevent the birth of further PI calves
• Testing for BVD and culling PI animals without delay

Herd biosecurity to prevent infection

The following biosecurity measures will help to prevent the introduction of BVD into the herd:

• Keep a closed herd
• If buying cattle, purchase from BVD-accredited herds
• If purchasing from non-accredited herds, quarantine and blood test before introducing new animals into the herd; be aware of the risks of buying pregnant cattle
• Double fence the farm’s perimeter to prevent contact with neighbouring cattle

Eradication of the disease from infected herds is possible by:

• Screening the whole herd
• Culling all PIs
• Vaccination
• Following biosecurity measures to prevent re-infection

Vaccination

BVD vaccination is designed to protect cows and heifers in early pregnancy to avoid infection and the production of PI calves.

Vaccination before cattle go through a market or to a show may also be useful to protect susceptible animals if the recommended course of vaccination has been completed in time.

A decision on whether to vaccinate, what with and when is best made with your vet.

Youngstock blood sampling (check-testing) must be carried out before vaccination to ensure that the resulting rise in antibodies does not lead to a positive test result.

Consider the risk factors for BVD infection for the herd, such as:

• Are there neighbouring holdings with cattle?
• Is there nose-to-nose contact with neighbouring cattle?
• Whether you buy in cattle or have a closed herd
• Whether bought-in cattle are of known BVD status
• Are cattle sent to shows?
• Are bulls brought in for breeding and is their BVD status known?

While vaccination may reduce the impact of BVD, it is important to understand that vaccination alone will not eliminate BVD, either from a herd or nationally.

Persistently infected cattle are so highly infectious and shed such large volumes of virus that they will continue to spread BVD even if the herd is vaccinated.

When administered correctly, vaccines are very effective.

It is essential that the manufacturer’s instructions for storage and use are followed as inadequately vaccinated animals in contact with PI cattle are at significant risk.

Your vet can advise how to store, handle and administer the vaccine correctly, including the timing of boosters, to get the best results from vaccination.

Diagnosis and testing routes for BVD

There are several testing routes available for BVD, depending on individual herd circumstances and farm goals.

A decision on which testing option to use is best taken with your vet to get the greatest benefits from testing. 

Government funding for BVD testing is available to beef and dairy cattle farmers in England through the Animal Health and Welfare Pathway; speak to your vet if you think this is an option.

Tag and test

• If you opt to tag and test, all calves born in the herd should be tested for the virus by a tissue sample
• You can test the calves as they are born or all at once
• You must test all calves that are registered as born on your holding
• It is advisable to test any aborted foetuses, stillborn calves and animals that do not produce a live calf or abort a foetus to ensure these are not persistently infected

Youngstock blood sample (check testing)

Whenever possible use option (a) below.

Where this is not possible, perhaps as a result of animals leaving the herd before the age of nine months, then options (b) and (c) should be followed in order.

Before deciding to do a check-test, speak to your vet to identify how many groups to sample in your herd.

If you calve twice a year, you may need to test your herd twice a year.

Your vet will decide how many animals need to be tested and can advise on how best to test herds with very low numbers of cattle.

(a) Five calves aged 9–18 months

Take samples of blood from at least five unvaccinated calves aged 9–18 months from each separate management group (see below for more information).

If you have fewer than five animals in this age group, you should test all of the animals in this category and count them towards the sampling quota in options (b) or (c), as appropriate.

(b) Five calves aged 6–18 months

If fewer than five of your unvaccinated calves are aged 9–18 months, sample all the calves in that age range.

Plus, take a sample of blood from at least five calves in total including animals in the age range 6–9 months, sampling a minimum of five calves in each separate group.

If you have fewer than five animals in this age group, you should test all the animals in this category and count towards the sampling quota in option (c).

(c) Five home-bred animals, including animals over 18 months

If you have fewer than five unvaccinated calves aged 6–18 months, then and only then, and on your vet’s advice, you may choose to use the following method:

Blood sample all of these calves, and a minimum of five unvaccinated older animals from each management group that have been on the holding since birth, so that a minimum of five animals have been sampled.

Discuss with your vet whether tag and test would be a more appropriate sampling strategy for your breeding herd in future years.

Milk testing

The milking herd can be screened for the presence of a PI animal(s) by testing a bulk milk sample for BVD virus.

Check with your laboratory on the maximum number of cows that can contribute to a bulk milk sample for the BVD virus test.

If the herd is too big or if a bulk milk sample tests positive, smaller pools and then individual milk or blood samples will have to be tested to identify the virus-positive animal(s).

Remember that in individual milk sampling, there is always a risk of cross contamination, which should be considered when analysing results.

If a PI is indicated from this milk screen, further testing will be required on the animals contributing to the sample to identify it. Individual testing is required for this.

Accreditation and support programmes for BVD

There are four programmes available through CHeCS (Cattle Health Certification Standards):

1. Accredited Free (AF) Programme – demonstrates the herd is free from BVD virus and allows the sale of cattle as accredited free of BVD virus.
2. Vaccinated Monitored Free (VMF) Programme – also demonstrates the herd is free from BVD virus and is protected by vaccination. The status provided by this programme is considered lower than that of BVD Accredited herds.
3. Dairy BVD Negative Programme – regular surveillance and biosecurity requirements provide reassurance of the absence of active infection with the BVD virus.
4. Eradication Programme – for herds where there has been a recent BVD infection to reduce the negative impact on herd productivity and achieve freedom from BVD.

Animal Health and Welfare Pathway

The Animal Health and Welfare Pathway (the Pathway) was launched in England in 2023 as a co-designed partnership with the Government working together with the wider industry. It offers a programme of funding to support continual improvements in farm animal health and welfare.

Funding is available to cattle farmers in England to test for BVD and obtain veterinary advice, specific to individual farm circumstances.

For further information and details about eligibility and how to apply, please visit:

BVDFree England Ltd. scheme closure

The BVDFree England scheme closed on 31 July 2024.

Current herd status certificates are available by emailing bvdfree.certificates@ahdb.org.uk. Please provide the CPH, farm name and trading name to process your request and allow five working days for a reply.

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