Photo: Wick Natzijl

Bovine virus diarrhoea is a highly contagious viral disease that is caused by the Bovine Viral Diarrhoea Virus. Because the virus is so contagious, it causes substantial damage on dairy farms. The BVD virus is split into two types, depending on its genetic makeup: BVDV-1 and BVDV-2. These types can be subdivided into different subtypes. The virus can be introduced to a farm in various ways. When animals come into contact with the virus for the first time, they start to produce antibodies. If a pregnant animal is infected during the first four months of pregnancy, the calf is born as a BVD carrier. BVD virus carriers are the main source of spread of the virus within the population. The BVD virus carriers secrete the virus for life and continuously. BVD virus carriers are also referred to as persistently infected animals (PI).