Fighting the bugs: the war on antimicrobial resistance
Antimicrobial resistance is a serious issue but the aquaculture sector is playing its part.
Since the early days of commercial fish farming, awareness of the dangers of AMR has grown significantly and the approach to using antibiotics is far more responsible.
In the UK, RUMA (the Responsible Use of Medicines in Agriculture Alliance) now publishes an annual report across all the leading livestock sectors, including aquaculture. The most recent report, published in November last year and covering 2023, summarises the fourth year of progress against the current set of antibiotic use targets which span 2021-2024.
RUMA says: “2023 has been another year of great effort and commitment from across UK livestock sectors in the responsible use of antibiotics; national usage figures remain low and largely unchanged from last year and the long-term AMR surveillance work carried out by the Veterinary Medicines Directorate (VMD) shows multi-drug resistance in animals is at its lowest level in a decade.”
The figures published in the latest UK-Veterinary Antimicrobial Resistance and Sales Surveillance (VARSS) Report, also released in November, show that antibiotic sales in food-producing animals remained at 25.7 mg/kg which maintains the 59% reduction since 2014. Meanwhile, sales of antibiotics which are the most critically important in human health only account for less than half a percent of total sales.
Introducing the report, RUMA Agriculture Chair, Cat McLaughlin, said: “These latest results from both the VARSS Report and in our RUMA Targets Task Force Report demonstrate that the collaborative, voluntary efforts over the past decade from the UK farmed animal, bird and fish sectors in addressing AMR are clearly paying off.
“The fact that AMR continues to decline with multi-drug resistance in animals at an all-time low should be applauded and should reassure everyone that the work on responsible use and stewardship is making a real and tangible difference.”
Salmon’s record
For the UK salmon industry, farmers recorded an overall increase in the volume of antibiotic used, compared to 2022, but use remains significantly below the levels recorded in 2020 and 2021. Increases were observed in both the freshwater and marine phases of production. Antibiotic treatments are still limited to a relatively small number of farms each year, with only 7.5% of freshwater farms and 9.8% of marine farms undertaking an antibiotic treatment in 2023.
The VARSS report provides more detail: In data collected by Salmon Scotland representing 100% of the industry, 3.7 tonnes of antibiotic active ingredient were used in 2023, representing 19.9 mg/kg. This is an increase of 7% (1.4 mg/kg) since 2022 and 24% (3.9 mg/kg) compared with 2017, when data was first published.
In 2023, 50% of use was oxytetracycline and 50% florfenicol. Between 2022 and 2023, oxytetracycline use reduced by 21% (2.7 mg/kg) whereas florfenicol use increased by 69% (4.1 mg/kg). Since 2017, oxytetracycline use has reduced by 28% (3.8 mg/kg) whereas the use of florfenicol has increased by three and half times.
Both of these agents are described as “lower priority” in terms of their AMR risk, while the higher risk oxolinic acid was not used at all during this period.
Salmon Scotland said: “The data records an increase in antibiotic use compared with 2022 but remains significantly below the levels recorded in 2020 and 2021. Increases were recorded within both the freshwater and marine phases of production. It is important to state that antibiotic treatments are relatively infrequent… the salmon sector continues to focus on a holistic and preventative approach to health management, including vaccination, antibiotic stewardship, biosecurity, and health and welfare planning.”
Dr Iain Berrill, Head of Technical at Salmon Scotland, told Fish Farmer: “Veterinary prescribed medicines are used responsibly, sparingly and only when required in the health and welfare interests of our fish.
“Although the sector faced significant environmental challenges in 2023, use of antibiotics remains low and we are committed to reducing use as low as possible.”
Trout continues to make progress
For the trout sector, RUMA says: “Usage of antibacterials decreased in 2023 to 6.9 mg/kg. The decrease is very positive news (following a disease outbreak in 2022 which saw a rise in antibiotic use to treat the fish) and the sector is back on track to keeping below 20 mg/kg. The trout sector has a proven track record of reduced usage over the past six years. The industry remains committed to decreasing usage overall and there is no prophylactic usage of antibacterials.
“The sector is still undergoing changes with a move towards larger fish production. Total tonnage has increased based on fewer but larger fish. Through the production cycle this means that farms buy fewer fry to grow on, stocking densities are then lower and fewer problems are seen.
“The extreme [warm] weather conditions remain a concern and can cause higher water temperatures which at times can prove challenging for some farms. The sector is looking at ways of mitigating issues caused by extreme weather.”
The VARSS report says the latest data demonstrates that a total of 0.09 tonnes of antibiotic active ingredient was used, representing 6.9 mg/kg, a reduction of 84% (37.2 mg/kg) between 2022 and 2023 and the lowest usage seen in the trout sector since electronic recording began in 2017. This follows the almost five times (35.2 mg/kg) increase between 2021 and 2022, which was linked to an outbreak of Aeromonas salmonicida on a small number of production sites.
The British Trout Association (BTA) has also been working with the Centre For Environment Fisheries and Aquaculture Science (CEFAS) on a “bug bank”, collecting and storing examples of pathogenic organisms, which it is hoped will lead to the creation of new vaccines in future.
Vaccine concerns
Vaccine availability in general has also been a topic of much focus in recent years with agricultural and companion animal sectors reporting shortages in vaccine availability, which in certain sectors is starting to curtail the veterinary response to some diseases.
Cat McLaughlin commented: “This is a red flag in efforts to tackle AMR and we are concerned that there could be a resultant increase in antibiotic usage to resolve the consequences of failing to effectively prevent disease threats through vaccination... we believe there is a need for political recognition of this risk and more collaboration to highlight the importance and availability of veterinary vaccines.”
Looking to the future, the next cycle of RUMA Targets (TTF3) will be developed over the coming year and will be launched this coming autumn.
A new UK five-year national action plan for antimicrobial resistance 2024 to 2029 and updated Veterinary Medicines Regulations (VMRs) will also be important references to help frame and shape the journey, challenge and opportunities of the TTF3 strategy, RUMA said.
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