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expert reaction to modelling study looking at antibiotic use in farm animals and antibiotic resistance in humans

Publishing in Royal Society Open Science, researchers using a mathematical model report that decreasing antibiotic consumption in food animals will often have limited benefits for human health.


Dr Peter Barlow, British Society for Immunology spokesperson, and Reader in Immunology & Infection, Edinburgh Napier University, said:

“Emerging antimicrobial resistance is a significant threat for human and animal health around the world, and it is a problem that requires coordinated and decisive global action to minimise the spread of drug-resistant pathogens.  It has been proposed that one way in which we could combat the spread of antimicrobial resistance is by reducing the amount of antibiotics used in animals that are part of the human food chain.
“This well-constructed study uses a simple mathematical model to look at what would happen to human health in the event that animals used in food production were given fewer antibiotics.  Their model suggests that this action alone would have little effect on levels of antibiotic resistance in humans.

“This finding is consistent with prior reports from the World Health Organization, stating ‘Antimicrobial resistance is a complex problem that affects all of society and is driven by many interconnected factors. Single, isolated interventions have limited impact1.
“I agree with the authors’ conclusions that several measures are required to reduce the emerging risk of antimicrobial resistance, and that their model would support this.  These measures can include increased surveillance and research, increasing awareness of the issue, effective sanitation and hygiene to prevent infection, and optimising the use of antimicrobials in humans and animals2.  However, I would caution against using this model as confirmation that we should not be focused on reducing the use of antibiotics in livestock, as it is extremely difficult to measure the effect of one intervention on a complex global problem.  Drug-resistant infections are a substantial threat to human and animal health and I believe reducing antibiotic use in our food supply will still be an effective action as part of a global strategy to reduce our reliance on antimicrobial medicines.”



Mr Daniel Parker, Lecturer at the University of Cambridge Veterinary School, said:

“While the authors themselves acknowledge that their model is simple and therefore may have limitations, this is an interesting paper which illustrates the complexity of antibiotic resistance and the fact that there needs to be a ‘One Health’ approach to the problem.  It does refute the claim by some that removal of antibiotics from animal production systems is the answer to antimicrobial resistance in humans.  It also raises the point that the drive for ‘antibiotic free’ is not necessarily beneficial for human health and makes any detrimental impacts on animal health and welfare arising from a drive towards ‘antibiotic free’ unjustifiable.  Therefore the RUMA approach of responsible use, which is ‘as little as possible, as much as necessary’ is the more considered and appropriate route when implementing antibiotic reduction programmes.”


Prof. Peter Lees, Emeritus Professor of Veterinary Pharmacology, Royal Veterinary College, said:

“This paper is to be welcomed and questions the unproven assumption that reducing the use of antimicrobial drugs in farm animal medicine will lead inexorably to lower levels of resistance in human pathogens and therefore that such reduction in veterinary use must be a good thing.

“That said, the answer to the basic question of antimicrobial resistance is hugely complex and full of a vast number of imponderables; to provide (even tentative) answers to the legitimate question, on the basis of mathematical equations, will turn out inevitably to be over simplistic.  As for all modelling procedures in general (not just this study), it is a case of quality data in, good prediction out; or alternatively rubbish in, rubbish out.

“The assumption seems to have been made that it is contact between animals and man in various forms which is the main driver.  This fails to take account of the spread into the environment of resistance factors following drug use in animals and potential subsequent transfer to human commensals and then pathogens – this potentially might be of major significance.”


Prof. Tim Morris, School of Veterinary Medicine and Science, University of Nottingham, said:

“The study ‘Modelling the impact of curtailing antibiotic usage in food animals on antibiotic resistance in humans’ suggests just curtailing the volume of antibiotics consumed by food animals has little impact on the level of resistance in humans, that reducing the rate of transmission of resistance from animals to humans may be more effective and that the rate of transmission from humans to animals should be considered.

“This is not a mandate for ignoring using antibiotics in animals, rather the study illustrates that an integrated ‘One Health’ approach across all species, including good basic hygiene, is needed to stem the tide of antibiotic resistance.

“It remains the case that increasing the use of any medicine that selects for resistant microorganisms and parasites, such as by more extensive routine use of antibiotics and wormers as part of agricultural intensification, or widespread trivial use of antibiotics in people, will inevitably lead to more medicines resistance.”


Prof. Roger Pickup, Associate Dean for Research in the Faculty of Health and Medicine, Lancaster University, said:

“This study acknowledges that antimicrobial resistance is a complex relationship between antibiotic usage in animal agriculture (including fish farms) and human populations.  The authors state that their modelling study suggests that by itself a reduction in usage in agriculture is not enough and that it has to be done in conjunction with a reduction in human exposure, which has to be a priority if resistance is to be reduced.

“The strength of the modelling study is that it should be taken to suggest that reduction in agriculture is not enough by itself but shouldn’t exclude a reduction in agriculture as part of the measure to reduce AMR – it reinforces the ‘One-Health’ strategy.

“This study highlights animal-human transmission rates as a key factor, however although this is not incorrect, it is the environment that tends to be ignored and this is ultimately where the pools of resistance reside, as we’ve shown in previous research1.  A mistake is also to compartmentalise humans, animals, hospitals, agriculture etc. as separate entities as we have shown them to be intimately linked2 with the environment playing an almost invisible role.  Reducing overall usage may reduce antimicrobial resistance but the environment will always be a key factor in its persistence.”

  1. Pickup, R.W and Rhodes G. (2006). Mechanisms for soil resistance. Science 312, 529.
  2. Rhodes, G., Huys, G., Swings, J., McGann, P., Hiney, M., Smith, P. and Pickup, R. W. (2000). Distribution of oxytetracycline-resistance plasmids between aeromonads in the hospital and aquaculture environments: implication of Tn1721 in the dissemination of the Tet A determinant. Applied and Environmental Microbiology 66, 3883-3890.


* ‘Modelling the impact of curtailing antibiotic usage in food animals on antibiotic resistance in humans’ by B. A. D. van Bunnik and M. E. J.Woolhouse et al. published in Royal Society Open Science on Wednesday 5 April 2017.


Declared interests

Dr Peter Barlow: “Dr Peter Barlow is funded by a grant from the Chief Scientist Office (Scotland) on a project investigating novel therapeutic approaches for respiratory viral infections.”

Mr Daniel Parker: “Daniel Parker is also on RUMA’s independent advisory Scientific Group, is a technical advisor to the British Poultry Council and an avian expert for the UK government.”

Prof. Peter Lees: “I have no conflicts.”

Prof. Tim Morris: “School of Veterinary Medicine and Science, University of Nottingham.  Non-executive on Defra’s Animal Health and Welfare Board for England.  Independent scientific consultant for Scientalis Ltd.”

Prof. Roger Pickup: “I only teach and research. Funding from research councils. I did sit on the NERC AMR grant awarding panel in 2015 and am a NERC awards core panel member.”

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