Bovine Viral Diarrhoea (BVD) is a pestivirus of cattle, it is a multifactoral disease of cattle causing many clinical signs. These include abortion, infertility, an immuno-supression that underlies calf respiratory and enteric disease and mucosal disease, a fatal wasting disease of adult cattle.
The disease is maintained by a small population of animals that become persistently infected (PI) with the virus. These PI animals are the major reservoir of BVDV and arise after becoming infected whilst in the uterus during early pregnancy.
Such infections remain throughout the pregnancy and, after birth, for the lifetime of the animal. Interestingly, although infection of the foetus results in a persistent infection, the mother is only transiently infected and becomes immune to the virus within 2-3 weeks. PI calves often die prematurely with respiratory or enteric disease but may also live a relatively normal life for several years; all the time, shedding large amounts of virus and acting as a reservoir of infection for in-contact cattle.
Thus, PIs are the main and most significant source of infection of BVD virus. Removing PIs from the population removes the source of infection and reduces the disease reproduction rate to the point that the virus cannot survive and the disease is controlled. There are other methods of virus maintenance and transmission, but they are considered of lesser significance in maintaining the disease.
Good diagnostic tests exist to detect both the PI animals and also the antibody status of the herd (i.e. to indicate whether BVD virus is present and circulating within a group of cattle). Good vaccines exist to protect breeding cattle and prevent the creation and birth of PIs. This disease is now eminently controllable.
This endemic viral disease of cattle is common in the UK and causes significant losses. Herds with BVD suffer infertility and reproductive disorders. Their health is poor, with problems such as pneumonia and scour. The disease may be insidious and protracted; you get used to living with the problem in the herd, to the point where you don’t realise how badly it affects you – until it is gone.
Control of BVD
Identification of the PI animal.
In order to control BVD effectively you must remove any PI animals. To start the process a bulk milk sample should be tested to look for PI animals in your herd, if positive we can start to blood sample individuals to find the PI animal. Speak to one of our Vets to arrange an individual protocol tailored to your herd.
All calves are now issued tagged and tested for BVD under the eradication scheme.
There are two vaccines available, one is a single injection which lasts for 1 year, the other consists of a primary course of 2 injections spaced 4 weeks apart, the second injection needs to be given 4 weeks prior to service to provide protection to the new foetus. This vaccine requires 6 monthly booster injections.
Please speak with one of our vets who will advise you on the most suitable course for your herd.