Bovine Viral Diarrhoea (BVD)

The Disease

BVD virus interferes with reproduction, detrimentally affects the unborn calf, contributes to calf pneumonia and other diseases by reducing their ability to fight off disease, and can cause severe diarrhoea. The most important effect is on pregnant cows, which may abort the foetus, or cause calf deformities. If the cow is infected during the first third of the pregnancy, the calf may become persistently infected with the virus (a 'PI' calf). The PI calf will shed the virus throughout its life, sometimes developing a severe fatal disease called mucosal disease (but often appearing healthy).

The Effect in Your Herd

Economic losses from BVD infection are a combination of detrimental effects on reproduction and conception rates and an increase in calf disease because the virus affects the immune system making calves more vulnerable to pneumonia and other diseases. Estimated financial losses are around £45,000 for a 100 cow beef herd over ten years, and  at least twice this figure for a similar sized dairy herd. (Figures from SAC BVD reference)

The Route of Transmission

The most important route is through the respiratory secretions from PIs, so screening for these and removing them is vital. Farmers can separate cattle with 3 metre fencing to eliminate nose-to-nose contact from neighbouring farms, and/or vaccinate the herd to prevent pregnant animals from becoming infected. Bulls can shed the virus in semen for up to 10 weeks after infection, so should not be used for this time after exposure. Vaccination of breeding stock is used to prevent the production of further PIs whilst the disease is being eliminated from a herd.

• BVD Ear Tissue Sampling