Farmers are the ‘unfair target’ in drug resistance battle

Mention the phrase ‘antibiotic resistance’ to a member of the public, and immediately images of so-called ‘superbugs’, such as MRSA, come to mind, sparking mass panic that one day hospitals will be inundated with serious bacterial infections which cannot be treated by the modern medicines we have at our disposal.

It is sometimes an exaggerated risk, but one which has got regulators here, in the EU and as far afield as the US looking at ways to combat the rise in resistance.

Currently, the primary focus of their efforts is agriculture, and groups such as the Soil Association have been vocal in their campaigns to reduce the use of antibiotics in food production.

But is focusing on farming the right move? No, according to many scientists, as numerous studies have shown agriculture is not the main culprit when it comes to the rise of ‘superbugs’.

Despite that, the EU is set to tighten regulations on using antimicrobials on farms. Its campaign to combat resistance has seen the Veterinary Medicines Directorate (VMD) in the UK propose banning the direct marketing of antimicrobial medicines to farmers.

Momentum

“This is a very serious and complex issue and it is picking up a great deal of momentum internationally,” says John Fitzgerald, director of operations at the VMD.

Discussions are now under way in Europe over how to prevent a rise in resistance. One approach gaining considerable momentum is to ban the use of certain classes of antimicrobials, preventing vets and farmers from using them to stop resistance building.

The theory is that, only when resistance is widespread for those drugs farmers are allowed to use, will the banned ones be permitted, as they will then be more effective.

While the VMD has outlined its opposition to any such ban, it has, in its latest review of the Veterinary Medicines Regulations, outlined plans to ban the direct marketing of antimicrobial medicines to farmers.

Mr Fitzgerald admitted the ban would have ‘little effect’ on resistance in animals or humans, but said the VMD planned to implement the ban in a bid to appease regulators in Europe ahead of negotiations on further tightening of the rules surrounding antimicrobials.

The charge often aimed at farmers is that increased use of antibiotics in animals leads to an increase in resistance which could then be passed on to humans via the food chain.

That theory, however, ignores much of the science, according to one recently-published review. It points towards a far more complicated picture of how bacteria are transferred from animals to human, and vice versa.

Transmission

The review, led by Professor Ian Phillips from the University of London, said “in all cases, the hypothesis is that the food chain is the main means of transmission”.

However, Prof Phillips said that while this hypothesis is “attractive”, and there can be no doubt of the existence of a hazard, neither of these means the hypothesis is ‘correct or of universal significance’.

In fact, bacteria can be spread the other way, from humans to animals, as well as from many other sources, such as sewage and wild animals (see diagram).

Regardless of those other pathways, bacteria in food-producing animals does still pose a risk. But how much of a risk is a subject of some debate, with some scientists saying there is a negligible effect on human health.

Research by L.V Piddock in 2002 concluded that ‘clear evidence antibiotic-resistant bacteria from animals caused human infections which were difficult to treat is extremely difficult to find’.

That is a view backed by Prof Phillips, who claims much of the resistance we see in humans is caused not by over-use in agriculture, but in human medicine.

Excessive use

“The campaign against what has been considered excessive clinical use has been generally evenly directed at human and animal medicine,” he said.

“But there has been a concerted attack on the agricultural use of antibiotics, based on the assumption that all such usage is imprudent, since it might act as an important source of resistance in bacteria affecting humans.

“Although some antibiotics are used both in animals and humans, most of the resistance problem in humans has arisen from human use.

“Even if resistant pathogens do reach man, the clinical consequences of resistance may be small. The application of the ‘precautionary principle’ is a non-scientific approach that assumes risk assessments will be carried out.”

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