CABI Blog

One of a series of blogs written by CABI editors for One Health Day November 3rd 2016

Most antibiotics in livestock farming are used in aquaculture, but significant amounts are also used in terrestrial livestock species, particularly in poultry and pigs.

Most antibiotics in intensive livestock farming are used for non-therapeutic purposes

Approximately 70% of antibiotics are used for non- therapeutic purposes, i.e. many antibiotics are used in sub- therapeutic doses and over prolonged periods, which leads to the development of genes that confer antimicrobial resistance to animal pathogens. These genes can subsequently be transferred to human pathogens and it is estimated that 75% of recently emerging diseases in humans are of animal origin.

Antimicrobial resistance (AMR) problems are further exacerbated by the fact that antibiotic resistance genes were found in bacteria long before antibiotics were ever used on super-pathogens in farm animals.

AMR is a worldwide problem, which clearly affects both animal and human health, and hence it is truly One Health issue.

Antimicrobial resistance and O’Neill’s Review
Recognising that the problem is severe and rapidly growing, the UK Government’s Department of Health and the Wellcome Trust commissioned a Review on Antimicrobial Resistance¹ in July 2014. The aim of the review, chaired by macroeconomist Jim O’Neill, was to examine the growing threat of AMR from an economic perspective and to recommend solutions. The review was published on 19 May 2016.

According to the report, antimicrobial drugs are becoming less effective and the world is not developing enough new ones to keep up. Drug-resistant infections and super-pathogens could kill 10 million people a year by 2050 – the equivalent of one person every three seconds. The report concluded that a comprehensive global action plan is needed to highlight the problem.

Antimicrobial drugs are rapidly becoming ineffective

The document sets out 10 areas to tackle antimicrobial resistance globally. Recommendations include targets set by individual countries for antibiotics use in agriculture, giving governments the flexibility to decide how they will reach lower levels. Quicker progress is needed on banning or restricting antibiotics that are vital for human health from being used in livestock farming.

The Review included eight thematic papers that address different aspects of the problem of AMR. These are as follows:

• Antimicrobial Resistance: Tackling a crisis for the health and wealth of nations (published in December 2014);
• Tackling a global health crisis: Initial steps (February 2015);
• Securing new drugs: The pipeline of antibiotics (May 2015);
• Rapid Diagnostics: Stopping unnecessary use of antibiotics (October 2015);
• Safe, secure and controlled: Managing the supply chain of antimicrobials (November 2015);
• Antimicrobials in agriculture and the environment: Reducing unnecessary use and waste, (December 2015);
• Vaccines and alternative approaches: Reducing our dependence on antimicrobials (February 2016);
• Infection prevention, control and surveillance: Limiting the development and spread of drug resistance (March 2016).

Use of antibiotics in livestock farming remains stubbornly high
The European Medicines Agency (EMA), however, recently published a report² showing that the amount of antibiotics used in animal production is not reducing and that many European countries are failing to put an end to excessive overuse of antibiotics in farming. In fact, the use of antibiotics in livestock³ still remains more than twice as high as in humans.

The EMA data show that the average European level of antibiotic use in livestock is 152 mg/kg, over three times higher than suggested level at the O’Neill’s Review, who recommended that high-income countries should aim for a short-term target of 50 mg of antibiotic per kg of livestock¹. Over 91% of European farm antibiotics were used for mass medication in feed or drinking water and a large proportion of this was for routine disease prevention in intensively farmed pigs and poultry.

In the 25 European countries which provided comparable data, sales of farm antibiotics per unit of livestock went down by just 2% in 2014 compared with 2013. If such a trend is maintained, it would take 65 years for Europe to reach the O’Neill’s target.

In 2014, overall use of the antibiotics classified as “critically important in human medicine” by the World Health Organization such as the antibiotic Colistin, which is used as a last-resort for treating infections in humans, increased to record levels.

These data indicate that the excessive use of antibiotics in intensive livestock farming is a direct consequence of the failure to ban routine preventative mass medication by most countries. It also confirms that reliance on voluntary approaches is not working.

The European Parliament has proposed a ban on all routine antibiotic use, but this has not yet been accepted by the Council of Ministers or the Commission. In January 2017, discussions are due to commence between the European Commission, the European Parliament and the Council of Ministers on future veterinary medicines legislation.

Very high levels of antibiotic-resistant pathogens are also present in meat
A recently commissioned study by the Alliance to Save our Antibiotics and carried out at Cambridge University, examined 189 pork and poultry meat samples of UK origin from the seven largest supermarkets in the UK. Resistance of E. coli isolates to a wide range of critically important antibiotics (CIAs) was tested.

High levels of resistance to CIAs were detected in chicken meat, with 24% of samples testing positive for ESBL E. coli (extended-spectrum beta-lactamase E. coli)⁴, a type of E. coli resistant to modern cephalosporins. This is four times higher compared with the levels found in a similar study in 2015, in which 6% of chicken meat tested positive for ESBL E. coli.

Over one-half of the E. coli samples from pork and poultry (51%) were resistant to Trimethoprim, which is used to treat over half of lower urinary-tract infections in humans and 19% of the E. coli samples were resistant to Gentamicin.

The findings provide evidence that the overuse of antibiotics used to mass medicate livestock is likely to be undermining the treatment of E. coli infections in humans, and highlight the need for an effective monitoring system and for improvements in antibiotic stewardship.

Antimicrobial resistance is truly One Health issue
One Health concept recognises that the health of people is connected to the health of animals and the environment. It has been described as “the collaborative effort of multiple disciplines – working locally, nationally and globally to attain optimal health for people, animals and our environment”⁵.

Excessive use of antimicrobials in intensive livestock farming is a global problem, which clearly affects both animal and human health. It is also clear that without a drastic reduction in the use of antibiotics in intensive livestock farming, we could be facing a grim post-antibiotic era, for the sake of producing cheap meat.

CABI and One Health Initiative
The use of antimicrobials in livestock farming and antimicrobial resistance, including antibiotic resistance, is a regular feature of CABI blogs:

Limitations of Voluntary Plan for Phasing Out Non-Medical Antibiotic Use in Farm Animals in USA

British Vets Resist “Political Measures” to Restrict Veterinary Use of Antibiotics

European Antibiotic Awareness Day Highlights Threat of Antibiotic Resistance

Workshop on “Food Security: Infectious Diseases in Farm Animals”- Invited Lectures, Day 2

CABI also publishes a number of authoritative scientific information resources, including CAB Direct, Global Health Database, Animal Science Database and VetMed Resource, which all aim to cover veterinary and human antibiotic resistance comprehensively.  At the time of writing, CAB Direct Database contains more than 10,800 references on antimicrobial resistance.

References:

• 1. O’Neill J, 2016. Review on Antimicrobial Resistance, 2016. Tackling Drug-Resistant Infections Globally: final report and recommendations. London: HM Government and the Wellcome Trust.
• 2. European Medicines Agency, 2016. Sales of veterinary antimicrobial agents in 29 European countries in 2014, Sixth ESVAC report.
• 3. ECDC/EFSA/EMA, 2015. First joint report on the integrated analysis of the consumption of antimicrobial agents and occurrence of antimicrobial resistance in bacteria from humans and food-producing animals.
• 4. Holmes A, 2016. Report: Antibiotic-resistant E. coli on supermarket meat – a serious threat to human health. Alliance to Save Our Antibiotics.
• 5. AVMA, 2008. One health: A new professional imperative. One Health Initiative Task Force Final Report. Shaumburg IL, American Veterinary Medical Association.

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