Antimicrobial Use Surveillance Indicators: Use and Practicality in Salmonid Aquaculture Settings

• Author / Creator

  Narbonne, Jacob

• Antimicrobial resistance (AMR) is a unique threat to One Health, and salmonid aquaculture industries are increasingly challenged to demonstrate responsible antimicrobial stewardship. Indicators and metrics to quantify antimicrobial use (AMU) data can comparatively enhance understanding of antimicrobial use patterns to inform stewardship policy. Global salmonid aquaculture growth and increased AMU creates the potential for the exchange of AMR between aquatic and terrestrial environments and humans, making AMU surveillance imperative for the salmonid aquaculture industry. The objectives of this thesis were to identify robust candidate AMU indicators for use in the salmonid aquaculture industry; apply robust AMU indicators to top salmonid producing regions using AMU and production datasets to summarize and describe annual AMU in each regions' salmonid aquaculture industry; and to analyze AMU in salmonid aquaculture using robust indicators and evaluate temporal and regional trends among top salmonid-producing regions. To identify current AMU metrics and indicators that could be applied to salmonid aquaculture AMU data, a systematic search strategy was applied to five databases: Medline, Embase, Agricola, CAB Abstracts, and Biosis. To be included, studies must have reported on at least one AMU surveillance indicator for use in animals. Total annual salmonid slaughter mass and AMU data were gathered from Norway, Chile, the United Kingdom (UK), and British Columbia (BC). Data for salmonid production and AMU were gathered for the comparison of unadjusted and biomass-adjusted AMU between 2004-2018. We applied the AMU indicator milligrams of active ingredient per adjusted and unadjusted Population Correction Unit (mg/APCU, mg/PCU) based on life-adjusted and non-life-adjusted annual salmonid slaughter and average production weights (mg/PCUSlaughter/AW) using data from these regions for 2004-2018 (2005-2018 for Chile). Antimicrobial use between regions was analyzed using descriptive statistics of unadjusted and adjusted AMU, ordinary least squares (OLS), and variance weighted least squares (VWLS) regression analysis.
  Over the entire study period, Chile had the highest mg/PCUslaughter (p<0.01), followed by BC (p<0.01), and then the UK and Norway. The Chilean mg/PCUSlaughter was consistently 2-6 times higher than British Columbia and 300-500 times greater than Norway for the entire study period. Norway had among the lowest annual overall AMU based on mg/PCUSlaughter estimates. The mg/PCUSlaughter decreased in Chile from 2015-2018 despite increasing production, whereas BC AMU fluctuated over the same period. Norway and the UK have maintained annual mg/PCUSlaughter/AW levels below 50 mg/PCU throughout the study period. The BC drug-specific mg/APCUSlaughter/AW showed greater drops in drug-specific use when the total slaughter biomass species composition shifted away from Pacific salmon to Atlantic salmon in 2004-2006. The mg/PCUslaughter varied significantly between salmonid-producing regions when evaluating all AMU between 2004-2018 in the VWLS model, which was required to account for unequal variance in biomass-adjusted AMU by region. Individual OLS models were fit to each region using year (centered on 2004) as the temporal variable and found significant changes in mg/PCUslaughter over time. British Columbian biomass-adjusted salmonid aquaculture AMU followed a quadratic relationship, declining until 2011 followed by a subsequent increase into 2018 (p<0.01). Chilean biomass-adjusted salmonid aquaculture AMU rose and fell throughout the study period, with a decline towards the end of the study. Norwegian biomass-adjusted salmonid aquaculture AMU declined linearly over the entire study period (p<0.01). Biomass-adjusted salmonid aquaculture AMU in the United Kingdom declined from the first yearly quartile (2004-2007) to the second (p<0.01) and did not increase or decrease significantly afterwards. Indicators based on the PCU improve the comparability of AMU between regions with different levels of salmonid production by standardizing annual AMU by measuring the size of the population. However, PCU-based indicators fail to account for differences in drug potency. If regions use different drugs with marked differences in mg/kg dosing, there can be large resulting differences in mg/PCUSlaughter or mg/APCU. However, indicators that account for drug dosages require a definition of an average treatment weight for aquaculture species. This research identified and described useful AMU indicators for reporting AMU data and determining how best to inform antimicrobial stewardship in the salmonid aquaculture industry. It also described possible reasons for differences in salmonid aquaculture AMU between regions. Future work will explore other AMU indicators and the use of AMR indicators in salmonid aquaculture, and the potential links between AMU and AMR/disease pressure in the context of salmonid aquaculture.

• Subjects / Keywords

  • Antimicrobials
  • Salmon
  • Aquaculture
  • Stewardship

• Graduation date

  Fall 2021

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-c2f2-7r70

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.