Immunosuppression as a factor in allowing mucosal disease to occur

In order to verify the role of immunosuppression in the pathogenesis of Bovine Viral Diarrhea Virus (BVDV) infection, two experiments have been carried out. In one experiment, calves previously infected with cytopathogenic (CP) or non-cytopathogenic (NCP) BVDV were treated with dexamethasone (DMS) 30 days later. In the other experiment, calves were simultaneously exposed to BVDV infection and to DMS treatment. In both experiments the DMS treated calves developed a more serious disease which in one calf was fatal. It was speculated that immunosuppression represents one of the most significant "key factors" in the occurrence of the bovine viral diarrhea/mucosal disease in cattle.