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it can appear in a herd in a number of different ways, depending on the herd's immune and reproductive status. Diarrhoea, respiratory infection, infertility and abortion are the most common clinical signs of the disease when the disease is first introduced, but the endemic situation in many herds, is more significant and has often been underestimated in terms of its affects on animal health and the economics of the farm.

The long-term effects caused by a herd infection are infertility, embryonic death, foetal mummification, abortion, congenitally damaged calves, weak or ill-thriven calves and persistently infected (PI) calves. Infection of a naïve cow in the first half of pregnancy will lead to infection before the development of the calf's immune system.Thus, the calf remains infected and is a source of infection throughout its life. BVD virus has also been identified as an immunosuppressive agent, and reduces the calf's own immune system, increasing the risk of infections such as respiratory disease and scours and making them much more difficult to treat.
 
Good diagnostic tests exist to identify both the PI animals and also the antibody status of the herd and this means we can identify if BVD is present on the farm, and if it is circulating within a group of cattle. Good vaccines also exist to protect breeding cattle and prevent the creation and birth of PIs. Because of this it is now possible to control BVD at farm level, and the disease could be eradicated completely from the farm. BVD control and eradication is relevant for any farm, whether the disease is there or not.  Even if a herd is uninfected it needs protection, as introduction of BVD into a herd that has not been previously exposed to BVD could be disastrous.
 
If you have any concerns over BVD please contact your local VET.

Livestock Health South East, funded by SEEDA through RDPE, are organising a number of meetings focusing on the effects of BVD and how best to manage the disease.
 
For further information http://www.livestockhealthsoutheast.org.uk