Until the introduction of a vaccine in the UK in 1996, the control of BVD was based on either keeping the herd free of disease by identifying persistently infected (PI) animals or by "immunising" heifers before breeding by exposing them to a PI animal. Most farmers, however, neither recognised nor controlled the disease in their herds. Since the development of an effective vaccine and good diagnostic methods, and the recognition of the significance of the disease in terms of reproductive loss and immunosuppressive effect, other control options have emerged (Brownlie et al., 2000; Curwen, 1999; Paton, 1999). The SAC Premium Cattle Health Scheme and the Herdcare National Cattle Health Scheme offer screening and eradication programmes and disease free status accreditation programmes for BVD. Several European countries have established BVD control or eradication programmes (Waage et al., 1994; Thibault et al., 1993; Timm, 1997; Greiser-Wilke et al., 1999; Ferrari et al., 1999; Nuotio et al., 1999).

The main risk factor for BVD infection in a herd is the existence of a PI animal within the herd due to the earlier infection of the dam during pregnancy. The PI animal then infects in-contact animals. Before the introduction of good vaccines, the PI animals were knowingly allowed contact with non-pregnant animals to allow them to be infected and develop natural resistance. This method was, however, unreliable and frequently resulted in disease outbreaks, reproductive loss and sub-optimal immunity in the herd.

Another major risk factor for BVD is the introduction of an acutely infected animal into the herd, such as a purchased breeding or fattening animal, a herd member returning from a show or a hired bull.

Less important but, in certain cases, significant risk factors can be contact with cattle from a neighbouring, infected herd, contact with other ruminants (sheep, deer) or contact with infected materials, such as veterinary instruments, veterinarian’s boots or clothing, other visitors, semen etc.