HoBi-Like Pestivirus Is the Most Frequently Detected Pestivirus in Cattle Across Different Regions of Brazil.

Pestiviruses are major viral pathogens of cattle worldwide, causing substantial economic losses and posing persistent challenges to animal health and productivity. Brazil hosts the world's largest cattle population and represents a strategic setting for the emergence and maintenance of bovine pestiviruses. Although previous studies have investigated pestiviruses in Northern, Northeastern, and extreme Southern Brazil, available molecular data remain geographically fragmented across this country of continental dimensions. HoBi-like pestivirus, HoBiPeV (HoBiPeV) has been frequently detected in Northern and Northeastern regions in previous molecular studies, whereas BVDV-1 and BVDV-2 are more frequently detected in the extreme South, leaving large areas with limited molecular information. This study investigated the occurrence and genetic diversity of pestiviruses in cattle from Northern Brazil and Paraná state, a key region connecting Southern and Midwestern Brazil. A total of 20,267 bovine serum samples were screened by RT-qPCR, including 10,832 from the Northern region (Acre, Amazonas, Rondônia, and Roraima) and 9,435 from Paraná State. Positive samples were subjected to sequencing and phylogenetic analyses. Pestivirus RNA was detected in 0.10% of samples (21/20,267), with HoBiPeV accounting for 90.5% of all detections. Notably, HoBiPeV predominated in both regions, reaching 93.3% of detections in Paraná, a state previously lacking molecular surveillance data. This study provides large-scale molecular evidence supporting the circulation of HoBiPeV across distinct cattle-producing regions of Brazil, where it was the most frequently detected pestivirus among the positive samples. These findings highlight the risk of silent HoBiPeV circulation that may escape BVDV diagnostic surveillance, which may facilitate undetected regional and potential undetected regional transboundary spread and pose a challenge to pestivirus control and eradication strategies. They also underscore the need for updated diagnostic approaches and continued genomic surveillance, as HoBiPeV circulation may be underestimated in South America and other cattle-producing regions.