16 Jun 2026
Clare Eames BVSc, MRCVS considers the latest understanding of this disease in cattle and how vets can work with farmers to control and eradicate it.
Clare Eames
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Image: Rob Steward / Adobe Stock
Bovine viral diarrhoea (BVD) remains one of the most significant endemic infectious diseases affecting cattle populations in the UK.
Despite sustained progress through national and regional eradication programmes, the virus continues to exert substantial impacts on cattle health, productivity, and farm profitability. Its economic consequences are frequently underestimated, and for practising vets BVD presents both a technical disease challenge and an opportunity to deliver measurable value through herd health planning, diagnostics and biosecurity advice.
This article reviews the latest understanding of BVD transmission routes, clinical impacts at both individual and herd levels, and the economic implications for UK cattle enterprises, set against the evolving policy landscape of BVD control and eradication.
The BVD virus (BVDV) is a pestivirus primarily affecting cattle. In the UK, the majority of circulating strains belong to the BVDV type 1 group, with several subgenotypes identified through molecular surveillance. Although type 2 strains have been reported, they remain uncommon. Pestiviruses are small enveloped RNA viruses that infect mammals; others that are closely related are border disease virus in sheep and classical swine fever virus in pigs.
Transmission of BVDV occurs through several routes; it can be present in any body secretions, including nasal discharge, saliva, semen, blood, faeces, urine, tears and milk. Spread is mainly by direct contact, sexual transmission, transplacental transmission and fomites. Spread might also occur through biting insects such as midges and nuisance flies.
Indirect transmission via fomites is a significant consideration for vets moving between both animals and farms. The virus can be transferred mechanically through contaminated equipment, clothing, vehicles, veterinary instruments and needles. While BVDV does not survive indefinitely in the environment, it can survive outside the body for up to a few weeks dependent on environmental conditions, with damp, cold and dark conditions being favourable.
High levels of contamination combined with poor hygiene can facilitate spread – particularly between groups of youngstock on farm. Thorough cleaning between batches of animals on farms is essential to reduce contamination with fomites, and farm biosecurity advice should always include recognition of fomites on farm visitors, slurry spreaders, shared grazing, transport trailers and so forth.
BVD epidemiology, however, is dominated by the presence of persistently infected (PI) animals. These animals arise when a susceptible dam becomes infected with non-cytopathic BVDV during early pregnancy – typically prior to 120 days of gestation. At this early stage in development, the fetal immune system fails to recognise the virus as foreign, resulting in immunotolerance. Calves born under these circumstances are persistently viraemic, do not produce antibodies to BVDV and shed large quantities of virus throughout their lives.
PI animals are widely recognised as the most important reservoir and source of infection within and between herds. A single PI animal can maintain viral circulation in a herd due to continual viral shedding and, therefore, maintain sustained infection pressure. They will infect susceptible cattle through direct contact and shared environments.
In addition, transient infection of naive animals plays a role in BVD transmission. Acutely infected cattle may shed virus for usually one to three weeks, during which time they can infect in-contact animals.
Although transient shedders are less efficient transmitters than PI animals, they are epidemiologically important – particularly when introduced into naive herds or when infection occurs during early pregnancy.
A particularly challenging transmission scenario for identification of origin on farm is posed by movement of so-called “Trojan cows”. These are pregnant animals that were infected during early pregnancy that have mounted an immune response that has eliminated the BVD virus, but which are carrying a PI fetus. When such animals are moved into a BVD-free or low-prevalence herd, the birth of a PI calf can introduce infection despite apparent compliance with testing requirements.
The clinical manifestations of BVD are diverse and depend on the immune status of the animal, the timing of infection, pregnancy status and the presence of concurrent disease challenges.
One of the most significant impacts of BVD is on reproductive performance. Infection of breeding animals can result in early embryonic death, reduced conception rates and increased and irregular returns to service. Infection later in gestation may lead to abortion, stillbirth or the birth of calves with congenital abnormalities affecting the central nervous system, eyes or skeletal system. These reproductive losses often occur without obvious clinical signs of illness in the dam, making them easy to attribute to other causes unless BVD is actively considered.
The immunosuppressive effects of BVD virus are well documented and contribute substantially to its overall disease burden. Infection can impair both innate and adaptive immune responses, reducing the animal’s ability to respond effectively to other pathogens. In calves and youngstock, this immunosuppression is associated with increased prevalence and severity of respiratory disease and enteric infections. At herd level, this can translate into higher treatment rates, increased antimicrobial use and poorer overall health performance.
Acute BVD infection in immunocompetent animals is often mild or subclinical, presenting with transient fever, lethargy, reduced appetite and occasional diarrhoea. Milk yield reductions may be observed in dairy cows during the acute phase. While these signs are usually self limiting, their economic significance should not be underestimated – particularly when infection occurs during critical production or breeding periods.
PI animals exhibit a wide range of clinical outcomes. Some fail to thrive from an early age, showing poor growth rates, ill-thrift and increased susceptibility to disease. Others may appear outwardly healthy for months or even years, allowing them to remain in the herd and continue shedding the virus.
All PI animals that do not die or are not culled for other reasons will eventually develop mucosal disease, a severe and fatal condition characterised by erosive lesions of the gastrointestinal tract, persistent diarrhoea, dehydration, and rapid deterioration to death. Mucosal disease typically occurs when a PI animal becomes super-infected with a cytopathic strain of the virus, usually following spontaneous mutation.
At herd level, the cumulative effects of BVD infection include reduced milk production, extended calving intervals, increased calf mortality, higher culling rates and reduced lifetime performance of replacement animals. These impacts may be subtle and develop gradually, reinforcing the importance of proactive surveillance rather than reliance on overt clinical disease.
Understanding the true cost of BVD to a farm goes well beyond the initial veterinary bill. The disease imposes both direct and indirect costs that can accumulate rapidly, eroding profitability.
Much of the UK costings work was completed around 20 years ago and concentrated on infection in naive herds, but some more recent information is available; for example, in 2020, Schmitt-van de Leemput et al showed that failure to control BVD in endemically infected herds could be costing up to 169 litres of milk per animal per lactation1.
In 2017, Yarnell and Thrusfield completed a BVD economic impact systematic review. They reported that the economic impact ranges from £0 to £552 per cow per year. The range represents both endemic or subclinical disease in herds with stable BVD virus infection, and epidemic or severe acute infections such as in naive herds. The variations in figures for economic impact of BVD relate to the immune status of the herd and severity of the viral strain involved2.
Remember that as well as direct production losses, indirect costs exist, which may include increased veterinary costs, additional feed and housing for unproductive or poorly performing animals, and the economic hit of culling and then purchasing replacement stock.
Reproductive inefficiency represents a major component of BVD-associated costs. Extended calving intervals, increased barren rates and higher abortion losses directly reduce output and increase replacement costs. In dairy systems, reduced milk yield and impaired lactation performance further erode margins. In dairy, beef and suckler systems, poorer calf growth rates and increased mortality undermine system efficiency and profitability.
Additional costs arise from increased veterinary intervention, diagnostic testing and treatment of secondary diseases. The immunosuppressive nature of BVD often leads to higher incidence of respiratory and enteric disease, increasing labour demands and antimicrobial use. Opportunity costs also exist, associated with movement restrictions, delayed sales and potential reduced market value of animals from BVD-positive herds.
Economic modelling consistently demonstrates clear financial benefits from BVD eradication. Herds that successfully eliminate the virus typically experience improvements in fertility, milk production and youngstock performance. These gains often outweigh the costs of testing, biosecurity enhancements and, where applicable, vaccination.
At industry level, eradication delivers benefits through improved animal health, enhanced trade confidence and reduced reliance on antimicrobials, contributing to broader sustainability goals.
Nationally, it is estimated that BVD costs UK farmers around £61m per year2.
The UK approach to BVD control varies between devolved administrations, but all share the common objective of identifying and removing PI animals while preventing reintroduction. The compulsory programmes in Northern Ireland and Scotland have made significant inroads: in Scotland, 92 per cent of breeding herds are negative, and in Northern Ireland only three per cent of herds are BVD positive . Wales has introduced a mandatory testing scheme in the past two years, and a compulsory BVD eradication scheme is set to be introduced in England in 2027, so hopefully these nations will see further improvements in the coming years.
From responses to the National BVD Survey 2024, it is apparent that most respondents recorded improvements in herd health by engaging with their national BVD eradication programme; however, 44 per cent did not think they had seen a benefit from doing so. The most common positive benefits identified included an overall healthier herd, improved fertility and a decreased level of disease seen in calves.
Northern Ireland operates one of the most advanced and stringent eradication programmes. Recent regulatory changes have tightened movement restrictions and reduced grace periods following positive or inconclusive test results. These measures reflect an increasing focus on rapid PI removal and prevention of onward transmission, including recognition of Trojan cow risks.
Scotland has progressed through multiple phases of its eradication scheme, with increasing emphasis on targeted testing, herd status classification and enforcement measures. Economic assessments suggest significant benefits to both individual farms and the national industry as prevalence continues to decline.
Wales has implemented compulsory industry-led measures requiring annual testing and defined actions following detection of infection. The Welsh approach emphasises collective responsibility and long-term industry benefits, including improvements in animal welfare and environmental sustainability.
Until 2027 in England, BVD control remains largely voluntary, driven by industry initiatives, market requirements and herd health planning. While this approach offers flexibility, it places increased responsibility on veterinary practitioners to promote best practice and encourage proactive engagement with BVD control. Ahead of the start of a compulsory programme, government funding is currently available for farmers to have an animal health and welfare review, including BVD testing via an Improve Animal Health and Welfare agreement.
Across the UK, herd health schemes under the umbrella of CHECS (formerly known as Cattle Health Certification Standards) have also been beneficial for trade and to eradicate disease from herds. CHECS certifies and quality controls CHECS-licensed cattle health schemes in the UK and Ireland, and ensures that all the schemes operate to the same set of technical cattle health standards.
Since its initiation in 1999, more farmers now than ever use a CHECS scheme to work towards having a healthier herd rather than solely to gain accreditation health status prior to sale.
Veterinary surgeons play a central role in all aspects of BVD control, from diagnosis and surveillance to farmer education and strategic planning. Effective use of all the diagnostic tools available, including antigen testing, serology and bulk milk analysis, allows vets to tailor control programmes to individual herd circumstances.
Biosecurity advice is a critical component of veterinary input. This includes guidance on quarantine protocols, testing of purchased animals, management of Trojan cows and mitigation of fomite transmission risks. As eradication programmes progress and prevalence declines, preventing reintroduction and managing transient infections become increasingly important.
Vaccination remains a useful adjunct in some herds – particularly where biosecurity risks cannot be fully mitigated. However, vaccination should be integrated into a broader strategy focused on identification and removal of PI animals, rather than viewed as a standalone solution.
Finally, veterinarians are well placed to communicate the economic rationale for BVD control, helping farmers to understand both the hidden costs of infection and the long-term benefits of eradication. This advisory role is likely to become even more important as regulatory frameworks evolve and industry expectations increase.
BVD continues to pose significant clinical and economic challenges to the UK cattle industry. Its complex transmission dynamics, often subtle clinical presentation and long-term impacts on productivity mean that it remains a priority disease for veterinary intervention.
While substantial progress has been made through coordinated eradication efforts, sustained vigilance is required to prevent reintroduction and achieve lasting freedom from infection. For UK veterinary practitioners, BVD offers a clear opportunity to deliver value through evidence-based diagnostics, strategic herd health planning and informed biosecurity advice.
Successful control not only improves animal health and welfare, but also delivers tangible economic and sustainability benefits for cattle enterprises and the wider industry.
Clare Eames has worked in the south-west since qualifying from the University of Bristol in 2001. She works part time at Synergy Farm Health and farms with her husband the rest of the time. Clare is particularly interested in regenerative farming and improving whole farm health.