Bovine Viral Diarrhoea (BVD) is a highly contagious viral disease in cattle caused by the pestivirus. The virus is maintained within a cattle population by animals Persistently Infected (PI) with the disease. BVD can be spread directly by infected animals, or indirectly such as by visitors or equipment contaminated with the virus.
A large proportion of BVD infections occur after birth, with animals becoming transiently infected (TI) before recovering. Transiently infected cattle may show no clinical signs, whereas other cases may result in reproductive problems in adult cattle and difficult to treat cases of scours and pneumonia in calves.
An unborn calf infected with BVD virus in the first 120 days of pregnancy, unless it is aborted or reabsorbed, is likely to be born PI. These PI animals are the greatest source of BVD infection to other cattle, as they shed high levels of virus throughout their lifetime. An animal cannot become PI after birth.
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If cows and heifers become infected within the first 120 days of gestation, the unborn calf may become persistently infected or PI. A calf will only become PI if its mother is infected during pregnancy; it cannot become PI after birth.
PIs will shed high quantities of BVD virus into their environment for life. They are the most significant source of infection to other cattle.
Within infected herds, PIs often only account for 1 or 2 out of every 100 animals. It is contact with these PI animals that leads to infection of other animals within your herd, causing the signs listed above.
Please note that the BVDFree Scheme is not in a position to advise farmers on their specific BVD control plans. These should be discussed with a vet.