Interventions to reduce antimicrobial use in livestock: a systematic review and evidence map.

Objective: To identify and describe government policy targeting veterinary antimicrobial use and antimicrobial resistance in production animals globally and to map these interventions to identify evidence gaps. Methods: We searched MEDLINE, CAB Abstracts, Web of Science and ProQuest Dissertations and Theses Global databases from inception to April 2025 for studies that quantitatively assessed the impact of government-enacted policy interventions by measuring the change in antimicrobial use (for example, mg/kg biomass, mg of active ingredient or defined daily doses for animals) or antimicrobial resistance in production animals or humans. Two reviewers independently completed screening, data extraction and risk-of-bias assessment for identified studies. Findings: We identified 40 policy evaluations, all originating from the World Health Organization (WHO) Region of the Americas, European Region or Western Pacific Region. No eligible studies from other WHO regions were identified. Most studies (35/40) evaluated legislative or regulatory interventions and 26 were primarily bans or restrictions on specific antimicrobial uses. Most (34/40) articles reported decreases in antimicrobial use in animals or in antimicrobial resistance in animals or humans that were associated with policy implementation. However, the studies were methodologically heterogeneous and had a high risk of bias. Conclusion: This systematic review and evidence map fill an important gap in knowledge supporting evidence-informed action on antimicrobial resistance. However, we identified relatively few quantitative evaluations of government policies targeting veterinary antimicrobial use or resistance, which highlights the need for additional, methodologically robust, policy evaluations.