Retrospective Analysis of Serological Positivity Patterns for Bovine Viral Diarrhea, Infectious Bovine Rhinotracheitis, and Leptospirosis in Brazilian Cattle Herds: Insights from a 16-Year National Dataset

Bovine viral diarrhea (BVD), infectious bovine rhinotracheitis (IBR), and leptospirosis are among the most important infectious diseases affecting cattle health, reproductive performance, and productivity worldwide. Understanding their spatial and temporal distribution is essential for supporting disease surveillance and control programs. This study aimed to characterize the distribution of serological positivity for these diseases in Brazilian cattle using a large retrospective dataset collected between 2005 and 2021. A total of 24,445 serum samples originating from 3,892 cattle farms distributed across 22 Brazilian states were evaluated. Serological testing for BVD, IBR, and leptospirosis was performed using established diagnostic methods, including enzyme-linked immunosorbent assay (ELISA), viral neutralization, and the microscopic agglutination test (MAT). Data were analyzed descriptively according to year, state, and geographic region. Among the analyzed samples, positivity frequencies of 64.34%, 58.64%, and 33.44% were observed for BVD, IBR, and leptospirosis, respectively. Higher frequencies of positive results for BVD and IBR were identified between 2008 and 2013. Spatial analysis revealed marked heterogeneity in the distribution of positive samples across the country. The South, Southeast, and Midwest regions accounted for the largest number of tested animals, reflecting greater diagnostic coverage. Nevertheless, elevated positivity frequencies were also observed in several states of the North and Northeast regions, suggesting active pathogen circulation in areas with comparatively lower testing intensity. Although the dataset does not represent a population-based prevalence survey, its extensive temporal and geographic coverage provides valuable insights into disease occurrence patterns in Brazilian cattle herds. The findings reinforce the importance of expanding diagnostic surveillance, particularly in historically underrepresented regions, and support the development of region-specific prevention and control strategies for economically relevant cattle diseases.