Unveiling Equine Abortion Pathogens: A One Health Perspective on Prevalence and Resistance in Northwest China.

Equine bacterial abortion presents substantial economic and One Health challenges; however, comprehensive epidemiological data from China are limited. This study sought to ascertain the overall prevalence of key pathogens-namely, Chlamydia spp., Coxiella burnetii, Salmonella abortus equi, and Brucella spp.-in equine populations in northwestern China. In this study, we aimed to further elucidate the characteristics of co-infections, profile antimicrobial resistance genes, and identify associated risk factors. Conducted as a cross-sectional analysis across four provinces, we collected 508 blood samples and 24 abortion tissue samples from 15 farms. Pathogen detection was performed using ELISA and real-time PCR, complemented by a targeted PCR panel screening for 29 AMR genes. The highest prevalence was observed for S. abortus equi (serology: 35.03%; molecular: 23.03%), followed by C. burnetii (28.94%; 15.35%) and Chlamydia spp. (18.90%; 14.17%). No PCR-confirmed cases of Brucella spp. were detected, despite low-level seropositivity. Notably, donkeys and horses aged 5-10 years exhibited higher positivity rates, and co-infections were common, particularly S. abortus equi + C. burnetii (n = 44). Among the 196 PCR-positive samples, extended-spectrum beta-lactamase (ESBL) genes were predominant, with CTX-M (n = 158) and TEM-1 (n = 106) being the most prevalent. Additionally, we identified a high prevalence of genes conferring resistance to fluoroquinolones (qnrA/B), tetracyclines (tetM), macrolides (ermA/B/C), and sulfonamides (sul1), along with sporadic occurrences of carbapenemase genes. This study presents the inaugural comprehensive analysis of pathogen prevalence and associated antimicrobial resistance (AMR) gene carriage in equine abortion cases in northwest China. The findings highlight the imperative for integrated serological and molecular surveillance, revealing a significant discrepancy between empirical therapeutic approaches and the prevalent resistance genotypes. Consequently, this research lays the groundwork for evidence-based biosecurity measures and antimicrobial stewardship within a One Health framework.