Submitted to: Journal of Veterinary Diagnostic Investigation
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/21/2010
Publication Date: 3/1/2011
Citation: Ridpath, J.F., Lovell, G., Neill, J.D., Hairgrove, T.B., Velayduhan, B., Mock, R. 2011. Change in predominance of bovine viral diarrhea virus subgenotypes among samples submitted to a diagnostic laboratory over a 20-year time span. Journal of Veterinary Diagnostic Investigation. 23(2):185-193. Interpretive Summary: Bovine viral diarrhea viruses (BVDV) cause a number of different diseases in cattle. Infection with BVDV results in reduced beef and dairy production. Vaccination is used to control BVDV infections. There are many different kinds of BVDV, these different kinds of BVDV are known as subgenotypes. To be most effective the BVDV subgenotypes used in the vaccines should be similar to the BVDV subgenotypes that are circulating in cattle. Previously published research suggested that the BVDV subgenotypes circulating in the United States may be changing. The purpose of this research was to look at BVDV strains isolated by one diagnostic laboratory over a 20-year time span to see if the prevalence of the different BVDV subgenotypes changed over time. It was found that the prevalence of the BVDV subgenotype that most closely matched the subgenotype in the most frequently used vaccines, BVDV1a, was decreasing in prevalence while the prevalence of a BVDV subgenotype not included in vaccines, BVDV1b, remained the same. This data suggests that vaccines in use between 1988 and 2008 did a better job of preventing BVDV1a than BVDV1b. The authors hypothesized that including BVDV1b strains in vaccines would improve control of BVDV.
Technical Abstract: While the causative agent of bovine viral diarrhea was initially categorized as one species, phylogenetic analysis revealed that these viruses belong to two different species, bovine viral diarrhea virus type 1 (BVDV1) and BVDV2, with 2 to 11 subgenotypes within each species. Distribution of species and subgenotypes has been shown to vary with geographic region. It is not known if distribution shifts over time. Surveys conducted between 1994 and 2008, reported three subgenotypes circulating among cattle in the United States; BVDV1a, BVDV1b, and BVDV2a. The average percent prevalence of BVDV1a, BVDV1b, and BVDV2a strains reported in surveys prior to 2001 were 21%, 43%, and 36%, respectively. Surveys conducted on viruses isolated after 2001 reported decreasing percentages of BVDV1a and BVDV2a strains with BVDV1b strains accounting for 75% to 100% of samples. Comparison of these surveys is confounded by differences in geographic location, collection methods, and sample type used in survey. The purpose of this study was to determine if there was a shift in the prevalence of BVDV subgenotypes in samples collected from the same geographic region and by the same laboratory over time. BVDV strains isolated in years 1988, 1998, and 2008, at the Texas Veterinary Medical Diagnostic Laboratory, Amarillo, Texas, were genotyped and prevalence of BVDV1a, BVDV1b, and BVDV2a strains were determined. Typing, based on phylogenetic analysis, was done on 148 samples. The strongest trend detected among these samples was a pronounced decrease in the number of BVDV1a strains over time.