Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: August 26, 2002
Publication Date: August 26, 2002
Technical Abstract: Bovine viral diarrhea virus (BVDV) strains can belong to one of two biotypes, cytopathic (cp) and noncytopathic (ncp). Biotypic differentiation is based upon activity in cultured epithelial cells. The cytopathic biotype is commonly associated with genomic insertions in the NS2/3 coding region. Biotype appears to have no correlation to virulence in acute infections. In the mid 1980's, a severe acute form of BVDV (SA BVDV) was reported. It is chracterized by elevated basal temperature (>40.5), lymphopenia (>60% drop), thrombocytopenia (>60% drop) and severe depletion of lymphoid tissues throughout the body. To date published reports of SA BVDV have been associated with noncytopathic BVDV genotype 2 (BVDV2) strains. Although only BVDV2 have been associated with SA BVDV, most BVDV2 strains are not highly virulent and only cause mild clinical disease in acute infections. While virulent BVDV2 strains are noncytopathic, insertions have been found in sequences flanking the NS2 coding region. Insertions have not been found in avirulent BVDV2 strains. When virulent BVDV2 strains are propagated in lymphoid derived cells lines (BL-3), cell cytopathology is apparent. Cytopathology was also observed with cp BVDV2 strains. Infection of BL-3 cells with ncp avirulent BVDV2 did not result in cytopathology. Cytopathology associated with cp strains was apparent within the first 48 hours after infection. Cytopathology associated with ncp virulent strains was apparent 96 hours after infection. This suggests that different mechanisms are involved in the cell death associated with cp strains and than in the cell death associated with ncp virulent strains. Further this research suggests that BVDV2 may be grouped into three biotypes, cp (based on cytopathology in epithelial cells and cultured lymphoid cells within the first 48 hours after infection), ncp (based on lack of cytopathology in both epithelial and lymphoid cells lines and lymphoid cp (based on cell death in lymphoid cell lines after 96 hrs post infection). The practical significance of these groupings is that the lymphoid cp biotype is associated with clinically severe acute infections in vivo.