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Bovine viral diarrhoea is a viral infection of cattle.

First published:
24 June 2024
Last updated:


BVD is one of the most important cattle diseases in terms of economic cost, productivity and welfare. Most herds in Wales are free of it. 

BVD causes: 

  • immunosuppression
  • abortion
  • infertility
  • failure to thrive 
  • death, particularly in calves

BVD control is centred on the identification of BVD Persistently Infected (PI) animals and their removal from the herd. PIs shed large amounts of virus throughout their lives and are the main source of infection. 

Eradicating BVD from those remaining herds would be worth millions of pounds to the Welsh cattle sector.

Clinical signs

BVD causes a complex of diseases in cattle. The most important of which can interfere with reproduction, affect the unborn calf and lead to mucosal disease. 

BVD virus can also cause enteritis during acute or transient infection. This is usually mild but occasionally severe enough to cause death, even in adult cattle. 

Transient BVD virus infection is associated with significant suppression of disease resistance. This can contribute to outbreaks of pneumonia or scours in calves, and other diseases.

The disease is mainly spread by persistently infected, or PI, cattle. These are born with the disease, having come into contact with the virus in the womb during the first 120 days of gestation. They will have BVD all their lives and they shed the virus extensively, infecting naive cattle directly and indirectly. 

Most die as calves but a few live much longer. Identifying and removing them from the national herd is critical to any eradication attempt.

Find more information in the leaflet from the Moredun Research Institute. You can also watch this video from Moredun Institute (on YouTube) on how to combat and prevent BVD in your herd.

Protecting your herd from BVD

BVD is spread easily and quickly by PIs (persistently infected cattle). The focus of Wales’s BVD eradication scheme is to find all PIs and prevent them from infecting other cattle. We know from other national programmes that if all PIs are removed, BVD can be eradicated.   

Infection can spread by other routes, but these are much less important than PIs in keeping disease circulating. The other routes for spreading BVD are:

  • transiently infected cattle, which produce less virus than PIs and only for 2-3 weeks and
  • contaminated surfaces; you can transport the virus on dirty hands, clothing, vehicles, and equipment.

To protect your herd from BVD infection, firstly prevent contact with PIs and transiently infected animals. The risk can come from:

  • within your herd
  • neighbouring herds over the fence
  • from cattle in the same show ring
  • the next pen at the market 
  • inside the same vehicle

Secondly, reduce the risk of bringing viruses onto the farm via contaminated surfaces. Good hygiene applies to all visitors to the farm, as well as to the keeper and any farm staff.

Protective measures to consider

BVD herd status

Cattle herds must update their BVD herd status annually and should investigate any signs of infection. Your vet will be able to advise you.

Careful sourcing of replacement cattle

If in doubt, check the animal’s status before buying. All cattle keepers in Wales must disclose the BVD herd status and the individual BVD status of cattle before selling.

“Trojan cows”

Take extra care if you are bringing in-calf cows or heifers into your herd. The unborn calf may not have the same BVD status as its mother and cannot be BVD tested until it is born. 

If unprotected females were exposed to BVD early in pregnancy, the calf will be a PI. If you have purchased an in-calf cow or heifer, calve her in isolation and test the calf for BVD virus as soon as possible. 

Tissue tagging allows a test for BVD virus at the earliest possible age. Don’t allow the calf to have contact with other cattle until it has a BVD-negative test result.


All livestock markets in Wales should be able to tell you the BVD status of the animal you intend to buy. 

Keepers and livestock markets must tell prospective buyers the BVD status of the animal and the BVD status of the herd the animal comes from before the sale. 

Remember that some diseases, including BVD, can spread easily between pens at a market. Consider keeping newly purchased cattle away from the rest of the herd for the first couple of weeks.


BVD vaccination can reduce the risk of infection entering the herd. Your vet will be able to advise.


Double fencing can stop contact with neighbouring cattle.


Show cattle can catch BVD from others at the event. Some PIs look healthy and cattle in the same class as yours may be carrying the infection. Consider vaccinating your show animals before the show season; your vet will be able to advise.


PIs can be taken directly to slaughter. When a transporter is doing multiple pick-ups of animals intended for slaughter, the PIs must not be unloaded at any of the interim premises before arrival at the slaughterhouse (direct movement). 

Ideally, any animals that are known to be BVD positive (PIs or suspect PIs) should be the last animals of a multiple pick-up round. If an emergency arises and BVD-positive animals must be unloaded, they must not be allowed to come in contact with cattle other than those that are also travelling to slaughter. 

If they have to be unloaded, it is advisable to clean and disinfect any area where BVD-positive animals have been before other cattle use the same hard standing or equipment.


The principal BVD legislation is The Bovine Viral Diarrhoea (Wales) Order 2024. This sets out the main requirements of the BVD eradication scheme in Wales.