Climate change and the global spread of antimicrobial resistance in livestock systems: a comprehensive review.

Climate change and antimicrobial resistance (AMR) are converging threats to livestock systems, food security, and public health. This review synthesizes mechanistic evidence linking climate variables to the proliferation of AMR in livestock and proposes integrated mitigation strategies. Elevated temperatures compromise livestock immunity, increase disease susceptibility, and drive antimicrobial use, while enhancing horizontal gene transfer (HGT) through increased plasmid stability, integrase activity, and bacterial stress responses. Altered precipitation and humidity influence biofilm formation, pathogen survival, and the mobilization of resistant bacteria and antimicrobial residues from manure into soil and water. Floods and droughts further concentrate or disperse resistance determinants across environmental reservoirs, creating transmission bridges between livestock, wildlife, and humans. Key evidence gaps include understudied climate variables (humidity, soil temperature), geographic blind spots (Sub-Saharan Africa, South Asia, Southeast Asia), and a scarcity of field data validating laboratory-based HGT mechanisms. Addressing these challenges requires climate-smart livestock practices (improved housing, adaptive breeding), enhanced antimicrobial stewardship (vaccination, probiotics, biosecurity), and sustainable waste management (anaerobic digestion, composting). Global coordination under a One Health framework, supported by robust policy mechanisms and targeted research funding, is essential to safeguard animal and public health from AMR in a changing climate.