Characterization of spp. circulating in industrial dairy cattle farms in Iran: a field study 2016 - 2023.

Bovine brucellosis, an infectious disease transmitted by and , presents a significant zoonotic risk for agricultural economics and animal health. The primary objective of this study was to present a comprehensive understanding of the prevalence and features of strains within the industrial dairy farming sector in Iran. Rose Bengal plate test, standard agglutination test, and indirect enzyme linked immunosorbent assay tests were used to confirm all seropositive animals. A total number of 1,311 bovine samples from seropositive animals including were collected from 224 farms in 21 provinces of different regions of Iran and examined. The discovered isolates were phenotyped and molecularly characterized. The isolates were all or . Bacteria analysis revealed that 70.53% of seropositive farms were tested positive for strains, predominantly biovar 1 (43.42%) and biovar 3 (27.11%). Geographical distribution revealed that biovar 1 was the most common in dairy cow farms (16 provinces), followed by biovar 3 (six provinces). Also, the prevalence of biovar 2, biovar 3, biovar 1, biovar 2 and RB51 vaccine were restricted to certain provinces. AMOS ()-polymerase chain reaction and Bruce-ladder PCR confirmed species identification. These results highlighted the complexity of bovine brucellosis in Iran and illustrated that was spread from small ruminants to cattle. This study provided important epidemiological insights for targeting future brucellosis control programs in the Iranian dairy farms.