Bovine Viral Diarrhoea Virus (BVD), despite the name, doesn’t often cause diarrhoea in adult cattle. The main effects are reduced fertility, abortions and general suppression of immunity that can lead to pneumonia, scour and other infectious disease.
Vet Pam Brown Vet, of Alnorthumbria Veterinary Group’s Wooler branch, said: “The incidence of BVD is not fully known in the UK but in recent years, the majority of farmers have become aware of the disease and most are now testing. Many are already vaccinating even if they do not fully understand the disease.”
Over the past two years, using funding from Defra, vets across the at-risk area have delivered a BVD scheme. The areas covered so far are the Coquet Valley, Forestburngate and northwards to the Scottish border on the west of the A697.
Scotland has had a compulsory BVD testing programme for two years; it is hoped a similar scheme will be rolled out in England.
Alnorthumbria Vets have now tested 82 farms in the area. This involves blood sampling five nine to 18-month-old unvaccinated animals from each separately managed group (two groups on most farms).
The samples are tested for antibody to BVD which at this age, they will only have if they have been exposed to the disease and mounted an immune response.
If only one or two out of 10 calves test positive, it is unlikely that there is a persistently infected (PI) animal present on the farm but they may have been exposed to the infection through poor biosecurity. If four or more out of 10 test positive, it is assumed that a PI is present on farm.
The confusing part is that calves that test positive for antibody are not the ones to worry about – they have been exposed to the infection but have mounted a healthy immune response.
The worrying calves are those that are antibody negative; PI calves are unable to make antibodies.
Cattle cannot become PIs – they are born this way when the dam is infected early in pregnancy. This is why, vital to the control of BVD, is vaccination of breeding cattle before going to the bull.