Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 10/27/1998
Publication Date: N/A
Technical Abstract: A bovine viral diarrhea virus (BVDV) strain pathogenic for neonatal pigs was serendipitously discovered in our laboratory. We were attempting to attenuate the virulence of the Miller #3 strain of transmissible gastro-ent s virus (TGEV) by serial passage on McClurkin swine testicular (ST) cell culture. However, the TGEV retained virulence after 70 in vitro passages which lead us to suspect contaminating agents were present in the ST cell culture. A BVDV contaminant (BVDV-C) was subsequently discovered and purified. Sequence analysis of the 5' untranslated region revealed 97.3% homology with BVDV strain NY1. The source of the BVDV-C is presumed to be commercially-purchased fetal bovine serum (FBS) used in the ST cell culture medium. Retrospective analysis revealed that the TGEV culture was contaminated with BVDV-C after the 15th in vitro passage which corresponded chronologically with the commercial purchase of several lots of FBS contaminated with BVDV. In subsequent pathogenicity studies with the purified viruses, neonatal pigs orally inoculated with BVDV-C or TGEV + BVDV-C developed severe diarrhea and enteritis with lymphocyte depletion of Peyer's patches, spleen, and thymus. Pigs inoculated with TGEV developed enteritis without lymphocyte depletion. Pigs inoculated with BVDV- NY1 did not develop diarrhea or lesions, but those inoculated with TGEV + BVDV-NY1 developed lymphoid lesions of variable severity in addition to enteritis. The results indicate that certain BVDV strains can be highly pathogenic in pigs and that nonpathogenic BVDV strains may act synergistically with TGEV to deplete lymphoid organs.