First reported by the Shrewsbury VI service in 1956 as a disease of sheep in the Welsh Borders, hence the name Border disease. Often restricted to a few farms where there can be serious problems. This condition may be underdiagnosed in the field. Dams infected one season appear to be immune to subsequent infection. Persistently infected lambs that survive are a source of infection to other sheep. There is evidence that BVDV from cattle can infect sheep and give rise to disease as described for BDV.