ShapeShapeauthorShapecrossShapeShapeShapeGrouphamburgerhomeGroupmagnifyShapeShapeShapeShape

Responsible use of antibiotics

by
01 November 2011, at 12:00am

RICHARD GARD reviews the issues surrounding the prescribing of antibiotics for food-producing animals and the need for scientific evidence about resistance

THE next few months are likely to be significant for the prescribing of antibiotics for food-producing and companion animals. European antibiotic awareness day is on 18th November and there is real political pressure from some quarters of the EU to reduce the volumes of antimicrobials administered to animals. Some member states perceive this as a way to reduce the risk of resistant strains passing to humans through the food chain, despite a lack of hard evidence that this is the case. However, as the belief that veterinary use causes problems gathers momentum in some quarters, there is a fear that products could be withdrawn for veterinary use as a risk reduction measure. If you feel that you’ve heard all this before and that there are so many committees involved that there will be no dramatic changes – think again. There is a real sense within some member states and other bodies that vets do not always prescribe responsibly and this belief could lead to some products being withdrawn, despite the negative outcomes for animal welfare that such a move would  bring. Within the UK, both the National Office of Animal Health and the British Veterinary Association are as one in alerting veterinary surgeons to the current situation and the risks this could represent to the availability of veterinary antimicrobials.

Split prescribing and dispensing

In April, a committee of MEPs, in considering resistance, discussed an option to split the prescribing and dispensing of antibiotics by veterinary surgeons, as is the case in some countries (e.g. Denmark). Some MEPs held the view that a vet financially benefiting from the sale of a product was not conducive to responsible prescribing. Intensive lobbying by veterinary representative bodies led to the withdrawal of the proposals but Harvey Locke, then president of the BVA, stated: “It is another stark wake-up call for members of our profession across the EU and beyond that we must not only take action on antimicrobial resistance, but we must be seen to be taking action.” One of the first responsible use initiatives was the species guidelines produced by RUMA (Responsible Use of Medicines Agriculture Alliance). The BVA produced the eight-point plan for the responsible use of antimicrobials  in 2009 and it is important that vets continue to act upon the advice and information detailed in the information poster (copies available from the website,  ww.bva.co.uk.). The BSAVA has recently released its “Protect” poster to help companion animal vets with guidance on the choice of antimicrobials. There is a plea to report suspected treatment failures to the VMD and the
Market Authorisation Holder through the Suspected Adverse Reaction Scheme. The reason for this is simply that a poor response to treatment may be the first  indication of resistance. In discussion with pharma vets, it is also clear that companies would wish to have the opportunity to be aware of treatment failures so that true resistance can be identified, rather than products being administered to the wrong animals at the wrong time at the wrong dose. There is a special note on the BVA poster that fluoroquinolones and third/fourth generation  cephalosporins should be reserved for clinical conditions that respond poorly to other classes of antimicrobials and where antibiotic sensitivity testing has been carried out. Further advice for use of these products is very clear: “Do not administer systemically to groups or flocks of animals except in very specific situations and special attention should be given to the risk of antimicrobial resistance as part of the benefit/risk assessment.” In August, the dairy department of Tesco wrote to veterinary practices advising them of revised standards for animal welfare to be met by its 720 milk suppliers. The letter stated: “Our new code of practice helps Tesco farmers better understand what customers are concerned about, and sets targets for improvements.” A complete range of measures is to be recorded and uploaded to a central database for comparative analysis. The data will be made available to veterinary surgeons on a read-only basis. Antibiotics prescribed for the cattle are to be graded into first and second line usage (this includes all products not listed as third line usage) and the farmer is to advise the number of individual treatments. Third line antibiotic usage is listed as fluoroquinolones and third/fourth generation  cephalosporins. The letter advises that “at this stage this is just monitoring, rather than any restrictions”. The  farmer record shows as a “rolling year to date average”. The likelihood is that other milk purchasers will also look to “monitor” antibiotic usage. Looking through some of the technical information, there is clearly a lack of hard data on the extent, or even actual occurrence, of resistant strains of bacteria to the antibiotics of concern
for human medicine developing and being transferred following veterinary use. That there are resistant strains
within human medicine is not in doubt, it is the link to antimicrobial use in animals that is uncertain. The European Food Safety Authority has a biohazard group, which has produced papers on the resistance issue in response to specific questions. The group indicates that “there are few studies that describe clear evidence of
direct transmission of ESBL (extended spectrum beta  lactamases) or AmpCproducing isolates from food  producing animals”.

Collecting data

Proposals are in hand to define the means of collecting the necessary scientific data throughout the EU. There are important issues over possible transmission routes of resistant strains and/or genes, with a need for clarification of the whole food production environment. Technical procedures for detection and characterisation of the resistant bacteria need to be harmonised across the EU and risk factors identified that contribute to the occurrence, emergence and spread. Together with the microbial science, an opinion is required “to identify and rank possible control options, taking into account the expected efficiency in reducing public health risk caused by resistant bacterial strains transmitted via the food chain or via the food animal production environment and consider the advantages and disadvantages of different options”. So, how do you view the risk of your prescribing of antibiotics contributing to resistant strains being developed and passing to humans? Is it all just a bit too genetic and plasmidbased and not quite linked to the dayto- day clinical and preventive options available to veterinary surgeons and farmers? Of immediate importance, it seems necessary for vets to reassure their
farmer clients that their use of antibiotics has not been shown to lead to untreatable disease in humans because of resistance. The rules and regulations on dosage and administration are there for good safety reasons and should be tightly followed. It is clear that the actual use of antimicrobials will need to be able to be demonstrated and
effort should be ongoing at practice level to accurately show
what is taking place. One of the difficulties is that a poor or nil response to antibiotic therapy is unlikely to provide good evidence of bacterial resistance. Experience of similar conditions, early treatment, past history and predicted outcome are all involved with an assessment of drug effectiveness on farm. Somehow, veterinary surgeons need to find a way of not only showing that they prescribe responsibly but also how to allay the fears of farmers, customers and politicians and show that good veterinary practice is beneficial to human health as well as animal health.

  • My thanks to Donal Murphy and Alison Glennon of NOAH and Ken Sibley of Virbac for sharing their technical, political and commercial awareness.