Bovine Viral Diarrhoea (BVD)

• ​BVD is a contagious disease of cattle occurring worldwide and many livestock farmers rate it among their highest economic and welfare concerns
• BVD is caused by a pestivirus, Bovine Viral Diarrhoea Virus (BVDV) and is responsible for a range of different clinical outcomes, including infertility and reproductive problems, respiratory and gut disease, and in some cases fatal Mucosal Disease (MD)
• The main effects occur when susceptible pregnant cows become infected with BVDV which can cross the placenta, colonising it and causing disease in the developing foetus
• If infection occurs in the first half of pregnancy, the foetus can die and be reabsorbed, presenting as infertility or ‘repeat breeding’. Some infected foetuses die later and may be aborted or stillborn. Many foetuses, however, survive to term. Some may be weak or grow poorly but most appear normal
• All calves surviving foetal infection in the first half of pregnancy are persistently infected (PI) with the virus, which is present everywhere in their bodies. They will not produce antibodies against BVDV
• Once colostrum-derived antibodies against BVDV have waned, PI calves will excrete virus continuously for the rest of their lives. They will rapidly infect other cattle that are in close contact. They may also develop MD (a fatal enteric disease) at any age
• If a PI cow breeds successfully she will always produce a PI calf
  Cattle that are not infected as foetuses cannot become persistently infected. These cattle may be transiently infected later, and their immune systems can be temporarily dampened down by BVDV, making calf pneumonia and scour more severe. Occasionally, virulent strains of BVDV can cause severe illness and death
  Bulls transiently infected with the virus may become infertile for several months and can transmit the virus to susceptible cows in their semen
• Control and prevention of the infection can be achieved by applying strict biosecurity procedures, vaccination and long term control strategies
• Several countries have successfully eradicated BVD​

Research at Moredun is focused on understanding the diversity of BVDV viruses in the UK, with the potential to help us understand how new outbreaks of BVDV might occur at late stages in the eradication. Diagnostic samples from PI animals are being collected and the sequence of a short region of the BVDV genome is defined for each sample. Between 2012 and 2018, about 4000 samples were analysed (about two-thirds of these from Scotland) and illustrate the distribution of BVDV strains within the UK and provide a baseline dataset for analysis later in the eradication.

Moredun is contributing to the Scottish BVDV eradication scheme. The Scottish cattle industry, supported by Scottish Government, embarked upon a Bovine Viral Diarrhoea (BVD) eradication programme in 2010. The impact of this programme has been significant: over 90% of Scottish breeding holdings now have a negative BVD status.

The programme is based on the use of herd- and individual level diagnostic testing to assure herd and animal BVDV status, with restrictions on the movement of PI cattle and on movement from holdings which have a non-negative BVDV status.

Current interests and future aims

We are interested in looking at how the diversity of BVDV strains is changing during the eradication campaign in Scotland, using the analysis of virus sequences and collaborating with scientists within the EPIC centre of expertise.

We are also interested in developing methods to sequence entire BVDV genomes from small diagnostic samples to provide high-resolution strain identification and to understand how the virus may change within and between animals.

This work is funded by the Scottish Government via the RESAS Strategic Research Programme and the EPIC centre of expertise in animal disease outbreaks.

For information about the eradication schemes currently operating in the UK please follow the links to the relevant websites below:

• Scottish BVD Eradication Scheme
• NI BVD Eradication Programme
• BVDFree England Scheme
• Welsh BVD Eradication Programme

BVD eradication in Scotland – Poster (2017)

PCR-sequencing of the BVDV genome reflects quasi-species variation defined by next-generation sequencing – Poster (2017)

Bovine viral diarrhoea virus loses quasispecies diversity rapidly in culture – Poster (2015)