​ Antimicrobial resistance from a vet’s point of view

That said, the topic of responsible medicine use is a constant feature of clinical discussions with clients. Writing in 2010, Henderson highlighted some of the potential misconceptions of how antimicrobials are used in the veterinary sector, saying ‘There is a school of thought, mostly in medical circles, that vets are guilty of antibiotic overuse in clinical situations where their capacity to modify the progress and treatment of the condition is limited, if not entirely absent.’ I would like to take this opportunity to demonstrate how we are working with our clients more closely than ever to address the issue of AMR.

The drivers of change

The publication of the O’Neill Review, in May 2016, saw the first figures for overall antimicrobial usage being suggested: ‘we see 50 mg/kg as a broadly reasonable target for high income countries to aim for in the short term.’ The report also set in motion the consideration of whether individual antimicrobial classes should be treated differently and whether targets should be broken down by animal type (e.g. poultry, cattle). In response to the report Defra committed to an overall target of 50 mg/kg across the animal sectors by 2018 (a 20% reduction in 4 years); it also committed to evidence-based goals for each individual livestock species sector being agreed by 2017.

In 2017, at the same time it was announced that the overall usage figures for 2016 were below the 50mg/kg target, the RUMA Target Task Force Report was published, laying out more details on how an overall reduction can be achieved through specific activities in each agricultural sector (Table 1).

Alongside the RUMA Target Task Force Report we have seen several other initiatives that have brought about changes in prescribing behaviour and on-farm usage. Within the UK farm sector, producers widely adopted assurance schemes to promote consumer confidence. The leading scheme is Red Tractor Assurance, which has a membership of over 40,000 beef, lamb and dairy producers across the UK. Whilst these schemes are not compulsory, they are frequently required for farms to market their products; for instance, 98% of UK dairy farms are registered members of Red Tractor. On 1 June 2018, new standards came into force with a specific focus on the responsible use of antimicrobials. The key requirements were:

• all farms must collate their annual medicine usage and review with a vet
• vet review of collated medicines usage data includes discussion on the use of critically important antimicrobials
• third- and fourth-generation cephalosporins, fluoroquinolones and colistin are used only as a last resort under vet direction, guided by sensitivity or diagnostic testing.

We have also seen retailers and first purchasers bring in contractual requirements for the farms supplying them; these started with antimicrobial usage reporting but have progressed to the banning of certain classes of antimicrobials. The focus initially was on the third- and fourth-generation cephalosporins and fluoroquinolones; however, we are now also seeing an increased focus on the macrolides.

Because of the changes in the assurance standards and retailer requirements we have seen increased client engagement with the topic of AMR, prudent use, and requests for medicines reviews. The discussions resulting from medicines reviews have resulted in significant changes in the antimicrobial sales patterns, especially in relation to high-priority critically important antimicrobials. Over 2018, our usage of third- and fourth-generation cephalosporins and fluoroquinolones has dropped by over 99.9%. Over the same period, we have seen an overall drop in antimicrobial usage across our business, so it has not simply been a case of swapping one product for another. This reduction in antimicrobial usage has been helped by changes in farm management practices, such as increased uptake of vaccination and disease eradication programmes, all facilitated by better engagement of farmers with their vets.

When we first started talking to clients about responsible use and antimicrobial usage reduction the most frequent concerns we were presented with revolved around animal welfare. Producers were concerned that they would not be able to treat animals and welfare would suffer. Our approach to this has always been about ‘as little as possible, as much as necessary’, with the message to clients not simply being to cut usage but being about avoiding the need for treatments in the first place and when antimicrobials are required ensuring that the right product is being used in the right way.

Let us take a look at one specific disease example, bovine respiratory disease (BRD), which is one of six conditions highlighted by the RUMA Targets Task Force Report as being a main reason for antimicrobial usage in beef cattle. BRD is a multifactorial syndrome that can be caused by both viruses and bacteria. Often the role of bacteria is as a secondary invader following an initial viral infection so there has been interest in how we can prevent the disease progression from the initial viral stages. The challenge in this situation is therefore identifying disease early enough that an antimicrobial treatment is not required. The traditional method for on-farm disease detection is for farm staff to evaluate the health of their stock subjectively, based on behaviour and appearance; this unfortunately has limited sensitivity (62%) for detecting BRD due in part to cattle’s natural tendency as prey animals to mask signs of disease and weakness. Detection is further hampered because the clinical signs being observed (e.g. depression, loss of appetite, respiratory character change and increased rectal temperature) are not specific for BRD. This can lead to cattle with BRD often being detected late in the disease process or not detected at all. This observation is supported by abattoir studies, which identified moderate to severe lung lesions in 35% of animals, of which 64% had no recorded treatments for BRD. The use of non-steroidal anti-inflammatory drugs (NSAIDs) alone in early cases of respiratory disease, as identified by temperature monitors placed in the ears of calves, has showed some promise, with 25.7% of cases treated with an NSAID alone not requiring any further treatment. The other focus for the control of BRD is vaccination; figures published in 2018 show that there has already been an increased uptake of pneumonia vaccines, with the percentage of cattle under 1 year old being vaccinated estimated at 29% in 2011, rising to 38% in 2017; however, it also highlights the large proportion of animals that are not receiving any pneumonia vaccines and the opportunity for further engagement.

Where next?

The EU commission’s 5 year action plan for AMR, published in 2011, highlighted 12 actions to be undertaken to help reduce the impact of AMR. In these action points the need for development of new effective antimicrobials for human use was highlighted; however, for veterinary medicine the action point was ‘analyse the need for new antibiotics in veterinary medicine.’ We are therefore unlikely to see new molecules for veterinary use and it is essential that we take steps to preserve the efficacy of what we have already. Most clinicians have probably resigned themselves to the fact that we are unlikely to see new compounds in the veterinary sphere, a point seemingly echoed by the animal pharmaceutical companies who are now positioning themselves as animal health providers rather than basing their business purely around drug development and sales. We now have the large companies increasingly investing in data collection and analysis, diagnostic and monitoring solutions, as well as seeing a shift towards the development of vaccines.

The responsible use of medicines and the reduction of antimicrobial usage remain key agenda for farm animal practice but need to be viewed as part of a holistic approach to animal health and welfare. Many of the successes we have had so far have been through veterinary education and engagement with our clients, but further sustainable reductions are going to require increased uptake of things such as vaccination, selective breeding for disease resistance and disease eradication programmes, as well as looking at the way in which we manage animals. The agricultural sector is under pressure to meet the requirements of an increasing population, but this must be achieved through management systems that meet both society’s demands for food production and their need to preserve the effectiveness of antimicrobials.