Border Disease Virus (BDV) belongs to the Pestivirus genus within the Flaviviridae family. BDV has a linear, positive-sense, single-stranded RNA genome of 12.3Kb in length. This virus is the causative agent of congenital disorder of lambs and reproductive problems in ewes. The virus has a tropism for foetal lymphoid tissue, hair follicles, and the central nervous system (CNS) and causes abortion in affected animals or the birth of weak lambs. Transmission occurs via contact with infected bodily fluids and excrement. Infection with BDV during pregnancy can lead to cross placental infection resulting in development of placentitis over a period of around 30 days. The majority of infected lambs die before weaning but those that survive can shed the virus throughout their lifetime, completing the transmission cycle. Animals infected in adulthood present with only mild symptoms including moderate fever, mild diarrhoea and decreased milk production.