Wild birds as environmental reservoirs of antimicrobial-resistant Salmonella: a global systematic review and meta-analysis

Background – The lack of consolidated global data on the prevalence and antimicrobial resistance (AMR) profiles of Salmonella in wild bird populations hinders our understanding of their epidemiological role as reservoirs and disseminators of resistant strains and impedes accurate evaluation of their potential implication for global public health. Methods – A random-effects meta-analysis was conducted to generate a pooled prevalence estimate of Salmonella and its AMR patterns in the global wild bird populations. Results – The pooled prevalence of Salmonella spp. in wild birds was 5.77% (95% CI: 4.21–7.54%), with the highest prevalence observed in Asia (10.13%), followed by Africa (6.66%) and Europe (6.14%). Serovar-specific analysis revealed that S. Typhimurium had the highest prevalence (4.12%), followed by S. Enteritidis (1.42%). Significant variation in prevalence across avian taxonomic orders has been detected, with Accipitriformes (6.85%) and Charadriiformes (6.15%) exhibiting the highest infection rates. Resistance to critically important antimicrobials ranged from 0% to 29.6%, with the highest prevalence observed for macrolides (29.6%), monobactams (22.9%), and penicillins (14.7%). In addition, a significant temporal increase in resistance was observed for key antimicrobials, including fluoroquinolones (R² = 19.21%, p = 0.003) and penicillin/β-lactamase inhibitors (R² = 66.75%, p < 0.01), suggesting an escalating environmental selective pressure. Conclusions – A significant temporal increase to some critically important antimicrobials highlights the growing influence of environmental selective pressures on AMR dynamics in wild bird populations. These trends suggest increasing environmental exposure to antimicrobial residues and resistant determinants, reinforcing the role of wildlife as sentinels and potential reservoirs for clinically relevant resistance with important implications for ecosystem health and public health surveillance. Given the interconnectedness between wildlife, livestock, and humans, the presence of AMR Salmonella isolates in wild birds represents a potential public health concern, even when resistance levels are low to moderate. These findings support the need for integrated One Health surveillance approaches and coordinated global policy interventions to monitor and mitigate the dissemination of resistance across ecosystems.