Imagine a world where we aren’t able to treat diseases because the drugs available no longer work. It’s a scary scenario but, worryingly, one we could face in the not too distant future, in both human and veterinary medicine. This potential disaster is down to a problem known as antimicrobial resistance.
What is antimicrobial resistance?
Antimicrobial resistance refers to any bacteria, virus, fungus or parasite (collectively known as micro-organisms) that’s no longer affected by one or more drugs (antimicrobials) that were originally effective at killing them or stopping their growth.
How does resistance occur?
When we use antimicrobial drugs, some of the target micro-organisms are likely to survive. The surviving ones can replicate and form a colony that’s resistant to the original drug, passing resistance on. In the case of surviving bacteria, they can also pass their genes for resistance directly on to other bacteria in their vicinity.
As a result, the use of antimicrobial drugs reduces the proportion of a population that’s non-resistant, which may eventually be outnumbered by resistant bacteria. It’s basically a case of survival of the fittest.
The biggest worry is the development of bacterial resistance to antibiotics. Before antibiotics were developed, bacterial infection was the leading cause of illness and death in people. Relatively soon after their introduction, it was noticed that some bacteria weren’t affected by certain types of antibiotic – they were resistant.
In the following 40 years, 29 new classes of antibiotic were created, so there was relatively little concern about this resistance. However, since then, very few new antibiotics have been developed. Ultimately, the resistance crisis has been caused by antibiotic overuse and misuse – for example, not completing a prescribed course.
What does it mean?
Antibiotic resistance is recognised as one of the largest threats to human health worldwide, and the impact on our horses and other animals will be equally far reaching. It’s been forecast that if the rate of antibiotic resistance continues, by as soon as 2050, human deaths attributable
to antibiotic resistance will outweigh any of the current causes of death, including cancer. Without antibiotics that work, we will be quite literally thrown back in to the pre-antibiotic ‘dark ages’ of medicine.
In addition to infections becoming more common and more serious, there’ll be a knock-on effect in other areas of medicine. Antibiotics are used routinely in the vast majority of surgical procedures in both humans and animals to prevent infection. This is called prophylactic antibiosis. Without appropriate prophylactic antibiosis, the risk of surgery skyrockets, whether it’s an emergency or routine procedure, in humans or animals. The risk of immunosuppressive therapy, such as chemotherapy for treatment of certain cancers, will also rise hugely.
Did you know? Some bacterial populations have developed resistance to more than one antibiotic. This is called multi-drug resistance and these populations of bacteria are commonly called superbugs.
A huge impact on horses
The effects of antimicrobial resistance could affect horses sooner than we think. The first outbreak of resistant bacterial infection in horses was reported in 1993. Studies have demonstrated that horses can be carriers of MRSA (methicillin resistant staphylococcus aureus), although there’s currently no data on the full extent of antibiotic resistance affecting horses.
In an attempt to slow the progression of antibiotic resistance, it’s likely that regulations will tighten in an attempt to preserve effective and new antibiotics for use in human medicine. It’s also likely that few, if any, new drugs will reach veterinary shelves for use in horses and it’s possible that some antibiotics that are currently prescribed may become restricted or even withdrawn for use by equine vets. This could seriously hinder vets’ ability to successfully treat some diseases.
An urgent need for change
The problems we’re facing have developed in an extraordinarily short period of time and, unless there’s a global effort to change the way in which we use antimicrobial drugs, they’ll only get worse. In particular, the use of antibiotics under any circumstance must be carefully considered. It’s in everyone’s interests to help combat this issue and the responsibility lies not only with prescribing vets, but with everyone else in the equine industry, too – including you.
Resistance can be slowed down by vets…
- prescribing antimicrobials only when needed
- performing laboratory tests to determine what type of bacteria is causing an infection and which antibiotic will be most effective against it
- choosing the most appropriate antibiotic, dose and course length
- investigating and treating the underlying cause in cases of recurrent infection
And by owners…
- having a good biosecurity plan for their yard to prevent infections being brought onto it, reducing the need for medication
- taking good general care of their horses
and ensuring they’re in the best of health to reduce the chance of infection
- giving antibiotics exactly as instructed by their vet and always giving their horse the full course to maximise the efficacy and reduce the chance of bacteria surviving
- never administering antibiotics without veterinary advice
A can of worms
Another important form of antimicrobial resistance that’s becoming a huge problem in the equestrian world is wormer resistance. The widespread use of wormers means that the risk of escalating resistance is high and the effects of resistance are already evident. Similarly to antibiotics, no new wormers are likely to become available anytime soon.
If resistance increases and wormers fail to control the numbers of gastrointestinal parasites, it could significantly compromise the welfare of our horses. To help slow the rate of resistance, it’s important that these drugs are used carefully and this responsibility relies heavily on owners and yard managers.
Treating all horses at regular intervals throughout the year is no longer considered to be an appropriate worming regime. Instead, you should carry out a faecal worm egg count every three months, then only treat horses with large worm burdens using an appropriate drug for the types of worm detected. You can also help reduce the need for wormers by controlling the number of parasites on your horse’s grazing and you can do this by using management practices such as…
- poo-picking regularly, ideally every day
- rotating paddocks regularly, allowing pasture to rest from late summer until spring, where possible
- cross-species grazing – putting animals such as sheep or cattle in your horse’s field can help break the lifecycle of the worms, because the worms that affect horses are unable to survive in these animals
- reducing over-crowding of pastures, because too many horses on the land leads to more droppings and, therefore, more parasite larvae in a smaller area. This increases the chance of horse infection
- harrowing rested pastures, especially in the summer. This breaks up the ground and exposes some of the larvae to sunlight, which kills them
Did you know? Studies have shown that carrying out faecal worm egg counts and only treating when needed leads to fewer wormers being administered to horses. And that’s not all. Another study showed that targeted treatment led to a financial saving ranging from £57–568 per yard each year on all 16 yards investigated, so worming in this way is a win-win situation.
Take action now
The rapid emergence of antimicrobial resistance is a serious threat to the health of ourselves, our horses and other animals. Every time an antimicrobial drug is used, the risk of resistance is increased, so it’s important that everyone plays their part in helping to ensure the drugs available are safeguarded so they can be used to save lives in the future.