Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 6/21/2004
Publication Date: 10/20/2004
Citation: Ridpath, J.F. 2004. Impact of BVDV type 2 on American BVD control approaches. In: Proceedings of the 2nd European Union International Symposium on BVDV Control, October 20-22, 2004, Oporto, Portugal. Available: http://bvdv-control.org/uploaded_files.asp?meny=22. Interpretive Summary:
Technical Abstract: In the early 1990's research groups in North America reported that a newly recognized severe acute form of bovine viral diarrhea virus infection, termed hemorrhagic syndrome, was associated with a distinct subgroup of BVD strains. This new subgroup was named BVDV genotype 2 or BVDV2. All BVDV strains previously characterized in the literature belonged to a separate genotype, BVDV genotype 1 or BVDV1. However, not all BVD strains identified as BVDV2 were associated with severe acute infections. One of the earliest studies characterizing BVDV2 strains found that 11 out of 76 had been isolated from persistently infected animals born to dams previously vaccinated against BVDV. Characterization of BVDV strains used in the vaccines revealed these strains belonged to the BVDV type 1 genotype. Subsequent surveys of BVDV strains isolated from clinical submissions to diagnostic laboratories and contaminated fetal calf serum suggested that the ratio of BVDV2 to BVDV1 strains in the U.S. approached 50%. Further, while antigenic cross reactivity has been noted between BVDV1 and BVDV2 strains, cross neutralizing titers are typically a log or more higher between BVD viruses within the same genotype compared to viruses from different genotypes. These observations prompted vaccine manufacturers in North America to produce vaccines against BVDV that contained antigens from both BVDV1 and BVDV2 strains. As of January 2004, at least five major biologics companies were marketing modified live and/or killed vaccines containing both a BVDV1 and a BVDV2 strain. Under experimental conditions these new vaccines offered improved protection against type 2 strains, however field data is still insufficient to assess their efficacy in practice. Questions regarding stability of multivalent BVDV vaccines and the benefit of include BVDV genotype subgroups are current topics of discussion among researchers and biologics manufacturers in the U.S.