BOVINE viral diarrhoea virus (BVDV) causes widespread infection of cattle populations worldwide and, even though the majority of infections go unnoticed, is an important disease (Brownlie and others 2000). BVDV infection impacts on animal welfare and causes significant economic losses (Ridpath 2010). Approximately 1 per cent of cattle are persistently infected with BVDV and are the major source of infection within a herd. Persistently infected cattle can be clinically normal yet shed high titres of infectious virus (Nettleton 2013). BVDV naive animals may succumb to acute infection, usually due to contact with a persistently infected animal. By contrast, the spread of the virus by animals with acute infection may be quite inefficient (Niskanen and others 2000). After acute infection, the virus is detected in blood and secretions for one to two weeks, and infection has been shown to induce suppression of specific …