Genomic Surveillance of BVDV in Southern Brazil: What Changed After a Decade in Rio Grande do Sul?

Bovine viral diarrhea virus (BVDV) is a major cattle pathogen associated with significant economic losses worldwide. In Brazil, the high genetic diversity of circulating strains represents an additional challenge for disease control. To update the molecular epidemiology of BVDV in southern Brazil, 16,198 bovine serum samples collected in 2020 through a national surveillance program were screened for pestivirus RNA by RT-qPCR. Forty-nine samples (0.36%) were positive and subjected to partial sequencing of the 5'UTR and N^pro regions. Phylogenetic analysis identified BVDV-1a (25/49; 51%), BVDV-1b (1/49; 2%), BVDV-1d (7/49; 14%), and BVDV-2b (16/49; 33%), with no detection of HoBiPeV. When compared descriptively with data from 2010 in the same region, BVDV-1a remained the most frequent subgenotype, while BVDV-2b also represented a substantial proportion of detections, contrasting with other regions worldwide. Although the two datasets are not directly comparable, and no statistically significant differences were observed, these findings provide an updated overview of circulating BVDV subgenotypes in Rio Grande do Sul. The absence of HoBiPeV contrasts with reports from other regions of Brazil and suggests a distinct regional pattern of pestivirus circulation. Overall, the results reinforce the importance of continuous genomic surveillance to monitor changes in viral diversity and support control strategies in cattle populations.