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
BVD will cause reproductive problems, failure to conceive, abortions and calf abnormalities. These cause economic losses but are not always immediately obvious to the farmer. BVD infection results in poor calf health because it affects their immune system making them vulnerable to pneumonia and other diseases. Estimated financial losses are around £45,000 for a 100 cow beef herd over ten years, and larger amounts for a similar sized dairy herd.

The Route of Transmission
The most important route is through the respiratory secretions from persistently infected (PI) calves, so screening for these and removing them is important. Farmers can separate cattle with 3 metre fencing to eliminate nose-to-nose contact from neighbouring farms or between separately managed groups, and/or vaccinate the herd to prevent pregnant animals from becoming infected. Infected bulls can shed the virus in semen for up to 10 weeks during the acute infection phase. If the level of BVD infection in a herd is very high, vaccination may be a useful additional tool to control disease.