COUNTERMEASURES TO CONTROL AND SUPPORT ERADICATION OF BOVINE VIRAL DIARRHEA VIRUS (BVDV)
Location: Ruminant Diseases and Immunology Research Unit
Title: Bovine viral diarrhea virus type subgenotypes isolated from cattle in the U.S. and Australia: prevalence and antigenic differences
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: December 16, 2008
Publication Date: January 25, 2009
Citation: Ridpath, J.F., Neill, J.D., Fulton, R.W., Kirkland, P.D. 2009. Bovine Viral Diarrhea Virus Type Subgenotypes Isolated from Cattle in the U.S. and Australia: Prevalence and Antigenic Differences [abstract]. 4th U.S. BVDV Symposium. Poster No. 10.
Aim. 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. The purpose of this study was to determine the prevalence of BVDV subgenotypes in the US and Australia and to determine if there are detectable antigenic differences between the prevalent subgenotypes.
Methods. Phylogenetic analysis was performed on two blinded panels of isolates consisting of 351 viral isolates provided by the Elizabeth Macarthur Laboratory, NSW and 514 viral isolates provided by Oklahoma State University. The Elizabeth Macarthur Laboratory (EMAI) panel was collected over a 20 year period from cattle in Australia and the Oklahoma State University (OSU) panel was collected between June 2007 and June 2008 from persistently infected animals identified in southwestern U.S. feedlots.
Polyclonal antisera was produced in goats tested free of BVDV and BVDV antibodies. Goats were hyperimmunized at 3 week intervals with 2 noncytopathic and 1 cytopathic strains of either BVDV1a, BVDV1b, BVDV1c, BVDV2a or BDV. Virus neutralization assays were then performed against 3 viruses from each of the five subgenotypes using the antisera produced against the five subgenotypes.
Results. Of the 351 isolates in the EMAI panel 11 (3.1%) belonged to the BVDV1a subgenotype, 1 (0.3%) belonged to the BVDV1b subgenotype, 338 (96.3%) belonged to the BVDV1c subgenotype, 4 (1.1%) belonged to the BVDV2a subgenotype and 1 (0.3%) was a border disease isolate. In contrast phylogenetic analysis the 514 isolates in the OSU panel revealed 62 (12.1%) BVDV1a strains, 387 (75.3%) BVDV1b strains, no BVDV1c strains, 65 (12.6%) BVDV2a strains and no BDV 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.