BVD is a highly contagious cattle disease. It is suggested that over 90% of UK herds have been exposed to BVD and Defra estimates it costs the cattle sector anything from £25-61 million a year.

The clinical signs aren’t always obvious but can result in reproductive problems and losses, weakening of the immune system, especially in young calves, and poor productivity.

If heifers or cows become infected early during pregnancy, the unborn calf may become persistently infected (PI). Such calves are reservoirs of infection and excrete a lot of BVD virus into their environment during their lifetime. They are the biggest source of infection to other animals. BVD is maintained within a herd by only a small population of PI animals; indeed there’s often only 1-2 PI beasts in every 100 animals in infected herds.

• Directly e.g. nose-to-nose contact with infected animals
• From infected dams to their unborn calves
• By buying PI animals, especially cows pregnant with PI calves
• Indirectly through contaminated kit, through farm visitors, through slurry, through biting insects, through co-grazing
•  Through semen from infected bulls

A large number of BVD infections occur after birth when animals become transiently infected (TI) before developing life-long immunity. TI cattle may show few clinical signs but infection could suppress their immune system making them more vulnerable to other common infections like scour or pneumonia.

BVD in early pregnancy causes embryonic death and irregular returns to oestrus, foetal death/abortion, mummification of the foetus, birth defects of the nervous system and eyes, weak/premature calves, as well as live PI calves. It’s not always easy to spot a PI animal; they may present with rough coats and stunted growth but will often appear completely normal. Within 6-18 months, however, the majority of PI calves will go on to develop a fatal condition called ‘mucosal disease’, characterised by severe diarrhoea.

A number of European countries have put in place national programmes for systematic control of BVD and some, like Norway, Sweden, Finland and Denmark, are virtually free of the disease.

Being in the 90% of herds exposed to BVD does not necessarily mean you have an active problem. The first step is to test milk samples from heifers and blood samples from beef and dairy calves to establish whether you have a current or historic problem.

To avoid low conception rates and embryonic loss/abortion and to prevent PI calves being born it’s necessary to stop cows being infected with BVD. Vaccination can help but strict biosecurity measures are essential as are tighter stock purchasing strategies. Removing all PI animals and infected bulls will reduce the level of virus circulating on farm.