Global trends in antimicrobial use in aquaculture

Aquaculture is a rapidly expanding sector, contributing significantly to global animal protein intake, particularly in low- and middle-income countries (LMICs). Its growth rate outpaces that of meat and dairy consumption. While the use of antimicrobials in aquaculture is documented, quantitative data on its extent across the diverse industry is lacking. This study addresses this gap by estimating global trends in antimicrobial use in aquaculture, aiming to inform surveillance and antimicrobial stewardship policies. The increasing use of antimicrobials in animal production, including aquaculture, is a major driver of antimicrobial resistance (AMR), a significant global health challenge. AMR leads to treatment failures, impacting animal welfare and sustainable food production. In aquaculture, the environmental pathway of antimicrobial distribution through water poses unique ecosystem health implications, affecting the environmental microbiome and potentially acting as reservoirs for AMR genes. While several geographically limited studies exist, comprehensive global data on antimicrobial use in aquaculture is lacking, hindering targeted interventions and policies. This study aims to fill this knowledge gap by estimating global antimicrobial consumption trends and projecting use to 2030, comparing these trends with human and terrestrial food animal antimicrobial use data.

The researchers conducted a systematic review of peer-reviewed and grey literature (2000-2019) on antimicrobial use in aquaculture, using search terms related to antimicrobials, their use, and aquaculture. They identified 25 studies from 12 countries, providing 146 biomass-adjusted use rates. These studies, along with qualitative reviews, informed the understanding of aquaculture antimicrobial use and influencing factors. However, the overall picture of global antimicrobial use in aquaculture remained largely undocumented before this study.

The study estimated baseline antimicrobial consumption and projected growth through 2030 by applying species-specific antimicrobial use coefficients to current and projected aquaculture production. A systematic review of peer-reviewed and grey literature identified 146 species-specific antimicrobial use rates (mg/kg of aquatic animal biomass). These rates were used to calculate mean antimicrobial use coefficients for six species groups (catfish, trout, tilapia, shrimp, salmon, and a pooled group). Aquaculture production data for 2017 and projections to 2030 were obtained from the OECD/FAO Agricultural Outlook and FAO FishStat, covering 33 countries, the European Union, and aggregated data for 232 countries and territories. A sensitivity analysis was conducted to identify and remove outlier surveys. The uncertainty interval (95% UI) was calculated using log10-transformed data. Finally, the study compared aquaculture antimicrobial use with previously published data on human and terrestrial food animal antimicrobial use.

Global antimicrobial consumption in aquaculture in 2017 was estimated at 10,259 tons (95% UI 3163–44,727 tons), projected to increase by 33% to 13,600 tons (95% UI 4193–59,295) by 2030. The Asia-Pacific region accounted for the largest share (93.8%) of global consumption in 2017, with China contributing 57.9%. Antimicrobial consumption intensity varied considerably across species groups, with catfish exhibiting the highest intensity (157 mg/kg, UI 9–2751), followed by trout (103 mg/kg, UI 5–1951), tilapia (59 mg/kg, UI 21–169), shrimp (46 mg/kg, UI 10–224), and salmon (27 mg/kg, UI 17–41). The pooled species group had a mean of 208 mg/kg (UI 70–622). All antimicrobial classes identified were classified as medically important. By 2030, global antimicrobial use across all sectors (human, terrestrial, and aquatic food animals) is projected to reach 236,757 tons. Aquaculture represents 5.7% of this total but has the highest use intensity per kilogram of biomass (164.8 mg/kg in 2017, 168.8 mg/kg projected for 2030), surpassing human and terrestrial animal consumption on an equivalent biomass basis. The most commonly used antimicrobial classes globally were quinolones, tetracyclines, amphenicols, and sulfonamides, many of which are critically important for human medicine. There was no significant association between production system intensity (intensive, semi-intensive, mixed) and antimicrobial use.

The study's findings highlight the significant and growing use of antimicrobials in aquaculture, particularly in the Asia-Pacific region, and the high intensity of use for some species. The reliance on medically important antimicrobials raises concerns about the potential contribution of aquaculture to AMR. The high intensity of antimicrobial use in aquaculture relative to other sectors underscores the need for targeted interventions and policies. While the study provides a valuable first global assessment, the limitations associated with data scarcity highlight the urgent need for improved surveillance and monitoring systems. The variability in antimicrobial use across countries and species necessitates a nuanced approach to antimicrobial stewardship in aquaculture.

This study provides the first global estimate and projection of antimicrobial use in aquaculture. Although aquaculture's share of global antimicrobial consumption is relatively small, the high use intensity and rapid growth of the sector warrant attention. The findings emphasize the critical need for improved data collection, particularly in LMICs, to enable more effective antimicrobial stewardship strategies. Future research should focus on developing and implementing standardized surveillance systems, exploring alternative approaches to disease management in aquaculture, and investigating the links between antimicrobial use and the emergence of AMR.

The study's estimates are subject to considerable uncertainty due to the limited availability of point prevalence surveys on antimicrobial use in aquaculture. Surveys from China, the world's largest aquaculture producer, are under-represented. The high diversity of farmed aquatic species and production systems introduces variability, potentially affecting the accuracy of the estimates. The assumption of constant mean use coefficients between 2017 and 2030 might oversimplify the dynamics of antimicrobial use. The study likely underestimates antimicrobial application through indirect pathways, such as the use of manure effluents in integrated farming systems.