ABSTRACT

Background and Aim: Antimicrobial resistance (AMR) is a major global health concern affecting humans, animals, and the environment. Although surveillance has traditionally focused on healthcare settings and livestock, wildlife is increasingly recognized as a potential reservoir, carrier, and indicator of antimicrobial-resistant bacteria and resistance genes. This review examines the ecological factors, movement patterns, and transmission pathways influencing AMR in wildlife, with particular emphasis on potential spillover to humans and domestic animals. Wildlife can acquire resistant microorganisms through contaminated water, soil, food, agricultural runoff, wastewater, and interactions with humans and livestock. Habitat fragmentation, urbanization, agricultural expansion, feeding behavior, and predator–prey relationships further influence exposure and opportunities for bacterial transmission. Local movements and long-distance migration may contribute to the geographical dissemination of resistant bacteria and resistance genes between ecosystems. Evidence from different wildlife populations has identified extended-spectrum β-lactamase-producing Escherichia coli in migratory birds, methicillin-resistant Staphylococcus aureus in wild mammals, and fluoroquinolone-resistant bacteria in primates inhabiting areas with frequent human contact. Marine and aquatic wildlife may also contribute to AMR circulation through exposure to wastewater, pharmaceutical residues, and other environmental contaminants. Horizontal gene transfer involving plasmids, integrons, and transposons further contribute to the persistence and dissemination of resistance genes within microbial communities. Humans may be exposed through direct contact, wildlife handling, hunting, and indirect exposure to contaminated water, soil, and food. However, detecting resistant bacteria in wildlife does not necessarily establish the direction or occurrence of transmission to humans. Key challenges include limited wildlife surveillance, inconsistent sampling methods, insufficient ecological data, and difficulty identifying transmission sources. Integrating wildlife monitoring with genomic analysis, environmental surveillance, and animal movement studies could improve understanding of AMR distribution and transmission risks. A coordinated One Health approach involving human health, veterinary, environmental, and wildlife sectors is essential to better characterize potential transmission pathways, strengthen surveillance, and develop effective strategies to reduce AMR spread across interconnected ecosystems.

Keywords: antimicrobial resistance, environmental contamination, horizontal gene transfer, migratory birds, One Health, resistance genes, wildlife reservoirs, zoonotic spillover.