Research and analysis

UK-VARSS 2021 Highlights

Published 8 November 2022

1. Antibiotic sales

1.1 Sales for food-producing animals in mg/kg

Sales of veterinary antibiotics for use in food-producing animals, adjusted for animal population, were 28.3 mg/kg; a 2.0 mg/kg (6%) decrease since 2020 and an overall 34 mg/kg (55%) decrease since 2014. This represents the lowest sales to date.

Bar chart depicting the sales in mg/kg for food-producing animals from 2014 to 2021:

• In 2014, the total mg/kg was 62.3 mg/kg
• In 2015, the total mg/kg was 56.5 mg/kg
• In 2016, the total mg/kg was 39.0 mg/kg
• In 2017, the total mg/kg was 32.1 mg/kg
• In 2018, the total mg/kg was 29.0 mg/kg
• In 2019, the total mg/kg was 30.4 mg/kg
• In 2020, the total mg/kg was 30.2 mg/kg
• In 2021, the total mg/kg was 28.3 mg/kg
• The 2021 mg/kg is 6% lower than the 2020 mg/kg, and 55% lower than the 2014 mg/kg

Sales of Highest Priority Critically Important Antibiotics (HP-CIAs) in food-producing animals account for 0.4% of total sales and have dropped from 0.14mg/kg in 2020 to 0.12mg/kg in 2021; an 18% decrease since 2020.

Line graph depicting the sales of HP-CIAs in food-producing animals from 2014 to 2021:

2014:

• Fluoroquinolones accounted for 0.35 mg/kg
• Third and fourth generation cephalosporins accounted for 0.19 mg/kg
• Colistin accounted for 0.12 mg/kg
• Total HP-CIAs accounted for 0.67 mg/kg

2015:

• Fluoroquinolones accounted for 0.35 mg/kg
• Third and fourth generation cephalosporins accounted for 0.17 mg/kg
• Colistin accounted for 0.13 mg/kg
• Total HP-CIAs accounted for 0.65 mg/kg

2016:

• Fluoroquinolones accounted for 0.23 mg/kg
• Third and fourth generation cephalosporins accounted for 0.14 mg/kg
• Colistin accounted for 0.02 mg/kg
• Total HP-CIAs accounted for 0.38 mg/kg

2017:

• Fluoroquinolones accounted for 0.16 mg/kg
• Third and fourth generation cephalosporins accounted for 0.11 mg/kg
• Colistin accounted for 0.001 mg/kg
• Total HP-CIAs accounted for 0.26 mg/kg

2018:

• Fluoroquinolones accounted for 0.15 mg/kg
• Third and fourth generation cephalosporins accounted for 0.06 mg/kg
• Colistin accounted for 0.0007 mg/kg
• Total HP-CIAs accounted for 0.21 mg/kg

2019:

• Fluoroquinolones accounted for 0.13 mg/kg
• Third and fourth generation cephalosporins accounted for 0.03 mg/kg
• Colistin accounted for 0.0002 mg/kg
• Total HP-CIAs accounted for 0.17 mg/kg

2020:

• Fluoroquinolones accounted for 0.1 mg/kg
• Third and fourth generation cephalosporins accounted for 0.04 mg/kg
• Colistin accounted for 0.00007 mg/kg
• Total HP-CIAs accounted for 0.14 mg/kg

2021:

• Fluoroquinolones accounted for 0.10 mg/kg
• Third and fourth generation cephalosporins accounted for 0.02 mg/kg
• No colistin is sold
• Total HP-CIAs accounted for 0.12 mg/kg

1.2 Sales for food-producing animals (tonnes)

In 2021 the total quantity of antibiotic active ingredient sold in the UK was 212 tonnes, the lowest sales to date.

Infographic depicting the total sales in tonnes for all animals:

• In 2014, 447 tonnes were sold
• In 2015, 406 tonnes were sold
• In 2016, 293 tonnes were sold
• In 2017, 246 tonnes were sold
• In 2018, 223 tonnes were sold
• In 2019, 229 tonnes were sold
• In 2020, 227 tonnes were sold
• In 2021 212 tonnes were sold, which is a decrease of 52% compared to 2014, and of 6% since 2020

Sales of HP-CIAs reduced by a further 0.19 tonnes (18%) from an already low level; a drop of 3.9 tonnes (81%) since 2014. Tetracyclines remain the most sold antibiotic class (32%), followed by penicillins (29%). Sales of HP-CIAs in all animal species represent a small proportion (0.4%) of total veterinary antibiotic sales.

Infographic depicting the tonnes sold in 2021 for each antibiotic class, and the difference in tonnes sold since 2014:

• In 2021, 68 tonnes of tetracyclines were sold in all animal species. Sales have decreased by 4.7 tonnes since 2020 and by 112.9 tonnes since 2014
• In 2021, 61 tonnes of penicillins were sold in all animal species. Sales have decreased by 1.4 tonnes since 2020 and decreased by 26.2 tonnes since 2014
• In 2021, 22 tonnes of trimethoprim/sulphonamides were sold in all animal species. Sales have decreased by 03.0 tonnes since 2020 and by 48.8 tonnes since 2014
• In 2021, 22 tonnes of aminoglycosides were sold in all animal species. Sales have increased by 0.1 tonnes since 2020 and decreased by 3.6 tonnes since 2014
• In 2021, 19 tonnes of macrolides were sold in all animal species. Sales have decreased by 2.7 tonnes since 2020 and decreased by 31.2 tonnes since 2014
• In 2021, 19 tonnes of antibiotics classed as ‘other’ were sold in all animal species. Sales have decreased by 2.4 tonnes since 2020 and by 7.7 tonnes since 2014
• In 2021, 0.75 tonnes of fluoroquinolones were sold in all animal species. Sales have decreased by 0.06 tonnes since 2020 and by 1.8 tonnes since 2014
• In 2021, 0.14 tonnes of third and fourth generation cephalosporins were sold in all animal species. Sales have decreased by 0.13 tonnes since 2020 and by 1.2 tonnes since 2014
• In 2021, 0 tonnes of colistin were sold in all animal species. Sales have decreased by 0.001 tonnes since 2020 and by 0.9 tonnes since 2014

2. Antibiotic usage

Antibiotic usage refers to the amount of antibiotics prescribed and/or administered per sector. The data have been collected and provided to the VMD by the animal industry on a voluntary basis.

2.1 Antibiotic usage by food producing animal species

Infographic depicting the antibiotic usage by food-producing animal species. Please note that the total coverage represents the percentage of animals covered by the data, except gamebirds which represents an estimate of the total percentage of antibiotic sales.

The total tonnage relates to the weight of antibiotic active ingredient using ESVAC methodology.

The total per unit, referred to as the mg/kg for 2021, relates to the amount of active ingredient standardised by kg biomass and calculated using ESVAC methodology.

Percentage doses refers to actual daily bird doses divided by 100 bird days at risk. Finally, please note for gamebirds, the industry estimates suggest that, due to Covid restrictions, gamebird rearing reduced by 30% during 2020.

• Pig production data covers >95% of pigs slaughtered in 2021. Total antibiotic usage was 87.3 mg/kg for 2021. Usage reduced by 17.7 mg/kg between 2020 and 2021 and by 69% since 2015.
• Meat poultry data covers 90% of the population. Total antibiotic usage was 42.6 mg/kg for turkeys, 13.7 mg/kg for broilers and 1.7 mg/kg for ducks in 2021. This is an increase of 16.8 mg/kg for turkeys, a decrease of 2.6 mg/kg for broilers and a decrease of 0.9 mg/kg for ducks since 2020 and presents a reduction of 81%, 72% and 89% for turkeys, broilers and ducks respectively, since 2014.
• Laying hen data covers 90% of the population. Total antibiotic usage was 0.33 % bird days in 2021. Usage reduced by 0.14 % bird days since 2020 and by 50% since 2016.
• Gamebird data covers 91% of the population. Total antibiotic usage in gamebirds was 8.9 tonnes in 2021. Usage increased by 3.1 tonnes since 2020 and decreased by 56% since 2016.
• Salmon data covers 100% of the population. Total antibiotic usage was 43.1 mg/kg in 2021. Total antibiotic usage increased by 13.8 mg/kg since 2020 and by 168% since 2017.
• Trout data covers 90% of the population. Total antibiotic usage in was 5.9 mg/kg in 2021. Total usage decreased by 47.9 mg/kg since 2020 and by 69% since 2017.

2.2 Highest Priority Critically Important Antibiotics by food-producing animal species

• Pig production data covers >95% of pigs slaughtered in 2021. Total HP-CIA usage was 0.03 mg/kg in 2021. Total usage reduced by 0.02 mg/kg since 2020 and by 97% since 2015.
• Meat poultry data covers 90% of the population. Total HP-CIA usage was 0.05 mg/kg in 2021. Total usage increased by 0.04 mg/kg since 2020 and decreased by 96% since 2014.
• Gamebird data covers 90% of the population. Total HP-CIA usage was 26.5 kg in 2021. Total usage reduced increased by 5.0 kg since 2020 and reduced by 59% since 2016.
• Trout data covers 90% of the population. Total HP-CIA antibiotic usage was 2.1 mg/kg in 2021. Total usage decreased by 2.1 mg/kg since 2020 and by 68% since 2017.

3. Antibiotic resistance in zoonotic and commensal bacteria from healthy animals at slaughter

3.1 Resistance in Escherichia coli from pigs

The UK can report mostly decreasing trends of AMR in indicator E. coli from healthy pigs at slaughter since 2015. Of the HP-CIAs, resistance to third generation cephalosporins is low and has declined since 2019; resistance to the fluoroquinolone ciprofloxacin has increased since 2015 but remains at low levels; and resistance to the quinolone nalidixic acid has remained low since 2015. No resistance has been detected to colistin over the monitoring period.

In 2021, the percentage of pig caecal samples positive for ESBL- or AmpC- producing E. coli on selective media reached the highest level seen so far during this monitoring programme, at 18.1% and 12.0% of samples respectively (30.1% combined). This result is unexpected and is being investigated further. This result is unexpected and is being investigated further. No isolates were positive for both phenotypes, and no carbapenemase-producing E. coli were detected during the monitoring period.

Infographic showing the percentage resistance of E. coli grown on non-selective medium:

• In 2015, 150 isolates were tested. 0% of isolates were resistant to third generation cephalosporins, 2.7% to fluoroquinolones, and 1.3% to other quinolones
• In 2017, 186 isolates were tested. 0% of isolates were resistant to third generation cephalosporins, 2.7% to fluoroquinolones and 2.2% to other quinolones
• In 2019, 208 isolates were tested. 2.4% of isolates were resistant to third generation cephalosporins, 3.4% to fluoroquinolones and 1.0% to other quinolones
• In 2021, 237 isolates were tested. 1.3% were resistant to third generation cephalosporins, 4.6% to fluoroquinolones and 1.7% to other quinolones

Infographic showing the percentage of caecal samples positive for ESBL- and/or AmpC-producing E. coli on selective medium:

• In 2015, 327 samples were tested, 25.1% of which were positive
• In 2017, 347 samples were tested, 19.3% of which were positive
• In 2019, 308 samples were tested, 18.8% of which were positive
• In 2021, 237 samples were tested, 30.1% of which were positive

3.2 Resistance in Salmonella spp. from pigs.

This year is the baseline year for testing the resistance of Salmonella isolates from caecal samples (rather than carcase swab samples). Of the HP-CIAs, no resistance was detected to third generation cephalosporins or colistin. Resistance to quinolones, including fluoroquinolones, was detected at low levels.

4. Antibiotic resistance – clinical surveillance

4.1 Resistance in Escherichia coli

Of the HP-CIAs, resistance to fluoroquinolones and third generation cephalosporins was low or not detected in 2021 for all animal species. Resistance to HP-CIAs has generally not increased for any of the animal species tested.

4.2 Resistance in Salmonella spp. from animals and their environment

Of the 4,507 Salmonella isolates tested, 67.5% were susceptible to all of the antibiotics tested. The number of Salmonella isolates from cattle, pigs, chickens and turkeys fully susceptible to the panel of antibiotics tested increased in 2021.

No resistance to third generation cephalosporins or fluoroquinolones was detected in cattle, pigs, sheep and turkeys. In chickens, resistance to third generation cephalosporins and fluoroquinolones was very low (0.1% for both). Resistance to ciprofloxacin was detected in 11 isolates: one from chickens, one from a dog, and nine isolates from feed.

A change to legislation in 2021 meant that Salmonella isolates from dogs became reportable under the Zoonoses Order in Great Britain. Of the 821 isolates tested, 34.6% were resistant to at least one antibiotic in the panel.

Infographic showing the percentage resistance to third generation cephalosporins and quinolones in 2021:

• For pigs, 0% of isolates were resistant to the third generation cephalosporins cefotaxime and ceftazidime and fluoroquinolone ciprofloxacin, and 1.1% were resistant to the quinolone nalidixic acid.
• For turkeys, 0% of isolates were resistant to the third generation cephalosporins cefotaxime and ceftazidime and fluoroquinolone ciprofloxacin, and 16.5% were resistant to the quinolone nalidixic acid.
• For broilers, 0.1% of isolates were resistant to the third generation cephalosporin cefotaxime, 0% to ceftazidime, 0.1% to the fluoroquinolone ciprofloxacin, and 3.9% were resistant to the quinolone nalidixic acid.
• For cattle, 0% of isolates were resistant to the third generation cephalosporins cefotaxime and ceftazidime, 0.1% to the fluoroquinolone ciprofloxacin and 1.2% to the quinolone nalidixic acid.
• For sheep, 0% 0% of isolates were resistant to the third generation cephalosporins cefotaxime and ceftazidime and fluoroquinolone ciprofloxacin, and 1.8% to the quinolone nalidixic acid.
• For dogs, 0.5% of isolates were resistant to the third generation cephalosporin cefotaxime, 0.4% to the third generation cephalosporin ceftazidime, 0.1% to the fluoroquinolone ciprofloxacin and 7.2% to the quinolone nalidixic acid.

4.3 MIC testing of veterinary pathogens

Following the introduction of MIC testing for key veterinary bacterial pathogens against commonly used clinical antibiotics in 2020, as an enhancement of the clinical surveillance programme, additional pathogens have been added to the core range in 2021.

This testing improves the usefulness of our AMR surveillance and also helps vets make better prescribing choices. Many isolates were fully susceptible to the panel of antimicrobials tested. Resistance was uncommon or not detected amongst antimicrobials which are often used as second or third line treatment options.

5. Background

5.1 How are sales data collected?

In the UK, from 2005 it has been a statutory requirement for pharmaceutical companies to report to the VMD the amount of antibiotic products sold for use in animals. The quantity of active ingredient is calculated from the amounts sold and the product characteristics. These sales data do not take into account wastage of veterinary antibiotics. However, this is the best currently available approximation of the quantity of antibiotics administered to animals in the UK.

5.2 How are usage data collected?

Data have been voluntarily provided by producers (pig, poultry and laying hen sectors), feed companies (gamebirds) and veterinary practices (gamebirds and fish). Usage data collection systems have been put in place to collect data from the British Poultry Council (meat poultry), the British Egg Industry Council (laying hen sector), the Game Farmers Association (gamebirds), the electronic Medicines Book (pigs), British Trout Association (trout) and Scottish Salmon Producers’ Association (salmon).

Usage data, i.e. the amount of antibiotics purchased, prescribed and/or administered, have the potential to provide much more precise estimates of use. The VMD has been working with the animal production sectors to develop sector-led data collection systems to monitor their antibiotic usage.

5.3 What is the Population Correction Unit (PCU)?

Trends in sales of antibiotics between years and different countries cannot be determined without taking into consideration variations in the number and size of animals that may require treatment. Therefore, sales data are analysed using the population correction unit (PCU).

This is a standard technical unit of measurement developed by the European Medicines Agency and adopted by EU countries. This allows data to be presented as mg of antibiotic per kg of livestock biomass. For more details see Understanding the mg/PCU calculation used for antibiotic monitoring in food producing animals

5.4 What are Critically Important Antibiotics (CIAs)?

Certain antibiotic classes are categorised by the World Health Organization (WHO) as critically important antibiotics for human use, of which several are designated as ‘highest priority critically important antibiotics’ (HP-CIA). In January 2020, the European Medicines Agency published new scientific advice on the risk to humans from antibiotic resistance caused by the use of highest priority critically important antibiotics (HP-CIAs) in animals. The report was prepared by Antimicrobial Advice Ad Hoc Expert Group (AMEG). Quinolones, third and fourth generation cephalosporins and polymyxins were classified as category B, where the use of these antibiotics should be restricted, as a result of their critical importance in human medicine. For more details see Categorisation of antibiotics in the European Union

5.5 How is antibiotic resistance interpreted?

Antibiotic resistance in bacteria isolated from animals is monitored through two distinct surveillance programmes: harmonised monitoring and clinical surveillance. The harmonised monitoring scheme is a UK-wide programme in which we test bacteria from the gut of healthy pigs and poultry at slaughter, giving us a representative picture of resistance in key livestock species entering the food chain. Clinical surveillance involves the testing of bacteria that have been isolated from clinical samples submitted by farmers and private veterinarians to government laboratories in England and Wales.

Susceptibility testing for harmonised monitoring is performed using broth microdilution to determine minimum inhibitory concentrations (MICs). Resistance is assessed using EUCAST (European Committee on Antimicrobial Susceptibility Testing) epidemiological cut-off values (ECOFFs). Results interpreted using ECOFFs are reported in full in supplementary material 3.

In the 2021 clinical surveillance programme, MIC testing was performed for important respiratory pathogens of cattle, sheep, and pigs, S. uberis isolates from bovine mastitis, S. suis isolates from pigs and E. coli isolates from chickens. The results were interpreted using veterinary clinical breakpoints (CBPs) when possible. Otherwise, resistance was assessed by disc diffusion techniques, and interpreted using BSAC (British Society for Antimicrobial Chemotherapy) human CBPs, where available. Full details of the methods used are available in supplementary material 1.