As antibiotics have been used more widely, more and more microbes have become resistant to them
McDonald’s, the world’s biggest restaurant chain, has committed to stop using antibiotics important to human medicine in chicken production for its USA restaurants by March 2017.
Meat produced without routine use of antibiotics is estimated at 5% of the US market, and growing fast.
Subway in the US aims to serve chicken raised without antibiotics across the US by next March, going antibiotic-free with turkey next year, and beef and pork by 2025.
The company is elevating its policy from “chicken raised without antibiotics important to human medicine” to meat “from animals that never received antibiotics”.
The trend is likely to kick off worldwide consumer demand for food products from animals that received no antibiotics over their lifetime.
According to Professor Chris Elliot, director of the Institute of Global Food Security, who led the UK government inquiry into the horsemeat scandal: “The industries that learn how to move towards antibiotic-free will prosper”.
Behind the new food trend is the rise in antibiotic resistance, to become a major public health problem.
In the last few decades, there has been widespread and increased usage of antibiotics in both human and animal medicine.
European figures for 29 countries in 2007 indicated the human consumption of antimicrobials was 3,350 tons, and sales of veterinary antimicrobials in 10 European countries was about 3,500 tons of active substance.
As antibiotics have been used more widely, microbes have become increasingly resistant to them. It is now commonplace for antibiotics which could be relied upon 20 years ago to fail.
The increased use of antibiotics is influenced by an increasing and ageing population, longer survival of people with complex illnesses, changes in food production systems, and other social and economic factors.
About one in every three patients in a major hospital is taking antibiotics.
In many cases, a patient may be on several different antibiotics simultaneously.
Infection associated with antimicrobial-resistant (AMR) bacteria results in significant increases in healthcare costs, sickness and mortality.
The European Centre for Disease Prevention and Control (ECDC) estimates that antimicrobial resistance results in 25,000 deaths and related costs in Europe, resulting from healthcare expenses and productivity losses, of over €1.5 billion annually.
Such is the level of concern around antibiotic resistance, the World Health Organisation is drafting a global action plan for combating antimicrobial resistance.
Relevance to agriculture
Antibiotic resistance is also a threat to animal health.
A new resistance gene (MCR-1) has been recently found in farm animals.
Found in virulent strains of E-coli and salmonella, it makesthem resistant to colistin, a decades-old antibiotic.
As newer, less toxic and better-researched antibiotics became available, colistin was hardly used in human medicine until recently.
But, as resistance has built up in newer antimicrobials, colistin has been elevated to become a last-line antibiotic in humans, to be used only when other treatments have failed.
Its use in people is increasing rapidly, as non-resistant alternatives become harder to find.
The use of antibiotics in animals is a potentially important risk factor for the development and spreading of resistant micro-organisms from animals to humans.
This risk arises through the consumption of produce (milk, eggs, meat) from treated animals, but also through contact with treated animals themselves (be they pet animals or food-producing animals) as well as their environment.
Many of the antibiotics used in treatment of animals are the same drugs as those used in human medicine, albeit that approximately 88% of veterinary drugs used in Ireland are older drug classes, including penicillins.
Antibiotics have been used widely in the treatment of animals since the 1950s, and are viewed by veterinary practitioners as being indispensable for treating animals.
The total tonnage of veterinary antibiotics used in Ireland was 87.2 tonnes in 2014.
All farming sectors have a responsibility to reduce unnecessary use of antibiotics, and ensure that antibiotics are used in accordance with best veterinary advice.
The Veterinary Ireland representative body, in their policy document on antimicrobial resistance (2014), identified potential contributors to the development of antibiotic resistance in animals in Ireland in each farming sector.
According to Veterinary Ireland, premix antimicrobials account for 32% of national use, and it is generally assumed that the pig industry accounts for most if not all of this total.
Veterinary Ireland say “the reality is that the pig industry has a significant problem on its hands with overuse, sub-therapeutic dosing and inappropriate use of antimicrobial agents”.
According to Veterinary Ireland, the route of antibiotic delivery in the pig sector is a major cause of concern.
“As most Irish pig farmers have not invested in specialist water delivery systems that are commonplace on mainland Europe, the primary route of antimicrobial delivery is via the feed system, as either purchased medicated-feed, or self-medicated home milling under license.
"Since most rations are supplied or milled to cover a number of successive weeks of production, if a farmer legitimately needs to medicate piglets for the first week post-weaning (to treat meningitis for example), he or she is likely to continue to use the same medicated feed for up to four weeks or more in some cases”.
Veterinary Ireland say: “Pig farmers need to invest in feed delivery systems that will accommodate more targeted delivery of appropriate treatments at the correct dosage and duration”.
They also recommend that pig veterinary practitioners promote more appropriate, prudent and responsible antimicrobial use, and say that, given the extent of antimicrobial use within the pig sector, “it is appropriate to consider the introduction of monitoring and surveillance programmes within the pig sector to gauge prescribing practices and usage levels.
This would highlight repeat prescribing, continuous prescribing and protracted prescribing practices. This data could be used to target certain use patterns, with a view to reducing antimicrobial reliance and usage in the pig sector”.
Cattle and Sheep
Veterinary Ireland say they have become increasingly aware that some animal farmers perceive that veterinary consultation/advice is an unnecessary cost rather than a benefit to business.
This leads to inappropriate use of antimicrobials.
For example, non-infectious calf scours are treated with antimicrobials, there can be incomplete duration of therapy, and insufficient dosage per kg.
HPRA, the Health Products Regulatory Authority, explains that the risk of antibiotic resistance increases if antibiotics are used at too low a dosage, for too short or too long a duration, too often, as a blanket measure in an untargeted manner, against bacteria that are not susceptible to the particular antibiotic, or against diseases caused by viruses or other germs which are not susceptible to antibiotics.
It’s clear that antibiotic resistance is a major problem facing both human and animal health, and action must be taken now.
In recent years, the European Medicines Agency (EMA), acting at the request of the European Commission, reviewed the indications and conditions under which some of the more modern antibiotic classes are used in veterinary medicine.
These reviews have resulted in more precise recommendations for use and new warnings which must be taken into account by vets when prescribing these antibiotics.
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