Mucosal disease is a fatal condition of cattle, characterised by oral and enteric erosions, which overlie the Peyer's patch lymphoid areas. Animals can die very rapidly but typically they show signs of anorexia, depression and diarrhoea for 2-5 days before death. Sometimes a longer period IS reported. They do not respond to treatment.
The pathogenesis of mucosal disease is complex and has shown interacting roles for both biotypes of the virus. The chronology of events is crucial.
The initial event is an infection of the susceptible (sero-negative) dam in early pregnancy The virus biotype, always BVDVnc, will cross the placentome and establish in the foetus. Before 110 days, the foetus is not immunologically competent and cannot recognise or eliminate the virus.