The Role of Migratory Birds in the Dissemination of Antimicrobial Resistance: A One Health Perspective.

Antimicrobial resistance (AMR) is a major One Health challenge driven by antimicrobial misuse in human medicine, veterinary practice, animal production, and polluted environments. Migratory birds move among wetlands, farms, wastewater-affected habitats, landfills, and coastal ecosystems and may acquire and redistribute antimicrobial-resistant bacteria (ARB) and antimicrobial resistance genes (ARGs) across ecological and political boundaries. This perspective synthesizes evidence on exposure sources, bacterial reservoirs, resistance determinants, cross-species interfaces, and surveillance priorities while explicitly distinguishing four claims: detection or carriage, persistence in individual birds, redistribution along migratory routes, and onward transmission to recipient hosts or environments. Published studies report multidrug-resistant Escherichia coli, Klebsiella pneumoniae, Salmonella spp., Enterococcus spp., and Campylobacter spp., with determinants including blaCTX-M, blaTEM, blaNDM, mcr, tet, sul, and qnr genes. The eight evidence groups summarized here constitute an illustrative, non-comprehensive selection; they are predominantly observational surveys or screenings, and none reconstructs a complete source-bird-destination-recipient transmission chain. Taxon-specific ecology modifies exposure: gulls and storks frequently exploit refuse and wastewater, waterfowl and shorebirds connect aquatic habitats, whereas passerines often reflect more local point-source contamination. Current evidence therefore supports migratory birds primarily as mobile sentinels and opportunistic carriers of anthropogenic AMR, while acknowledging possible natural or ancestral resistance in avian-associated microbiota. Future surveillance should combine longitudinal sampling, baseline cohorts such as pre-migratory nestlings, paired bird-water-soil-sediment sampling, whole-genome sequencing, plasmid profiling, telemetry, environmental DNA, wastewater-based epidemiology, and interoperable veterinary reporting. Practical mitigation requires antimicrobial stewardship, wastewater and landfill control, farm biosecurity, and coordinated veterinary, environmental, and public-health action.