|Vander Ley, Brian|
Submitted to: American Association of Veterinary Laboratory Diagnosticians
Publication Type: Abstract Only
Publication Acceptance Date: 8/21/2008
Publication Date: 10/23/2008
Citation: Ridpath, J.F., Vander Ley, B.L., Sweiger, S.H., Fulton, R.W., Kirkland, P.D. 2008. Prevalence and Antigenic Differences of Bovine Viral Diarrhea Virus Subgenotypes Isolated from Cattle in Australia and the U.S. [abstract]. American Association of Veterinary Laboratory Diagnosticians. p. 130. Interpretive Summary:
Technical Abstract: Bovine viral diarrhea viruses are segregated into two different species within the pestivirus genus, bovine viral diarrhea viruses type 1 (BVDV1) and bovine viral diarrhea viruses type 2 (BVDV2). While this segregation was first based on phylogenetic analysis, subsequent characterization of viral strains from the two species demonstrated antigenic differences. The practical significance of antigenic differences was evidenced by the failure of vaccines and diagnostics based on BVDV1 strains to control and detect, respectively, BVDV2 strains. Further phylogenetic analysis has revealed subgenotype groupings within the BVDV1 and BVDV2 species. Thus far twelve BVDV1 subgenotypes (BVDV1a, BVDV1b, BVDV1c, BVDV1d, BVDV1e, BVDV1f, BVDV1g, BVDV1h, BVDV1i, BVDV1j, BVDV1k, BVDV1l) and two BVDV2 subgenotypes (BVDV2a and BVDV2b) have been identified. The practical significance of segregation into subgenotypes is still a matter of discussion as to the impact on conferring cross protection to heterologous challenge and the ability of reagents in diagnostic tests to detect the broad range of subgenotypes. Different BVDV1 subgenotypes predominate in different countries. Phylogenetic analysis of 298 pestivirus isolates of bovine origin archived at the Elizabeth Macarthur Agriculture Institute in New South Wales, Australia revealed that 15 isolates (5.0 %) belonged to the BVDV1a subgenotype, 3 (1.0 %) belonged to the BVDV1b subgenotype, 272 (91.3%) belonged to the BVDV1c subgenotype, 4 (1.3%) belonged to the BVDV2a subgenotypes and 4 (1.3%) were shown to be isolates of border disease virus (BDV). In contrast phylogenetic analysis 514 bovine pestiviruses isolated from U.S. between June 2007 and June 2008 revealed 62 (12.1%) BVDV1a strains, 387 (75.3%) BVDV1b strains, no BVDV1c strains, 65 (12.6%) BVDV2a strains and no BDV strains. There is a least one commercial vaccine line available in Australia that is based on viruses belonging to the most prevalent subgenotype present in that country, BVDV1c. While the BVDV1b subgenotype predominates in the U.S., vaccine lines are based on BVDV1a and BVDV2a strains. Goats hyperimmunized with either 3 different BVDV1a, BVDV1b, BVDV1c, BVDV2a or BDV strains mounted serological responses with comparative antibody levels that correlated with subgenotype used as immunogen. That is, serum from goats hyperimmunized with strains from one subgenotype was better able to neutralize other strains from that same subgenotype compared to strains from a different subgenotype. Similarly, serological immune responses mounted by 40 co-housed feedlot cattle persistently infected with different BVDV strains suggested differential responses to strains from the same subgenotypes as the persistent virus compared to strains belonging to other subgenotypes. These studies suggest that there are antigenic differences between BVDV strains belonging to different subgenotypes. Further studies need to be conducted to determine if vaccine protection can be improved by basing vaccines on the BVDV subgenotypes that are prevalent in the region in which the vaccine is to be used.