DIAGNOSIS OF NATURALLY-OCCURRING BOVINE VIRAL DIARRHEA VIRUS-INFECTIONS IN RUMINANTS USING MONOCLONAL ANTIBODY-BASED IMMUNOHISTOCHEMISTRY

Formalin-fixed paraffin-embedded tissues from 50 spontaneous cases (39 bovine, nine ovine, two caprine) of bovine viral diarrhea virus (BVDV ) infection diagnosed by virus isolation were retrospectively examined for BVDV antigen by immunohistochemistry using anti-BVDV gp-43 monocl onal antibody (Mab 15C5). The cases were separated into enteric diseas e syndrome, respiratory disease syndrome, and abortion/ weak calf synd rome based upon clinical disease. The purposes of the study were to 1) compare routine virus isolation with immunohistochemistry in determin ing BVDV infection and 2) define tissue and cellular distribution of B VDV in various clinical manifestations of infection. In bovids, there was 100% concordance of virus isolation and immunohistochemistry using Mab 15C5 in cases of enteric disease (mucosal disease, acute and chro nic diarrhea, neonatal diarrhea), respiratory disease, and abortion. W hen laboratory tests were restricted to gastrointestinal tissue and/or feces, virus isolation detected BVDV in only 65% of cattle, whereas i mmunohistochemistry detected BVDV antigen in 100% of cattle. Immunohis tochemical detection of pestivirus was poor in cases of ovine abortion , ovine hairy shaker syndrome, and caprine abortion. The tissue distri bution of BVDV antigen was widespread in individual cattle with all cl inical forms of BVDV infection. Viral antigen accumulation was spatial ly correlated with tissue lesions (in the absence of other pathogens) only in the gastrointestinal tract, lymphoid tissue, lung, placenta, a nd eye. This study demonstrates the utility of immunohistochemistry us ing Mab 15C5 to diagnose BVDV infections in cattle with a broad spectr um of clinical disease.