The debate around use of antibiotics in farming is surrounded by conflicting and confusing information. This is our Farm Antibiotics Myth-buster which aims to debunks some of the misperceptions by giving you the facts.
A Government-compiled report released in 2015 compared 2013 data for human prescriptions and animal sales of antibiotics. It found that around 56% of antibiotics were used in humans and 44% in animals. It is judged that around 7% of the total is use in companion animals (pets). However, there are far more farm animals than humans in the UK – over a billion compared with 65 million humans. So comparing instead by mass, UK humans use around 2.4 times more antibiotics per kg of their weight than farm animals. A more recent European report finds that medical use of antibiotics in the UK is about average in Europe. By comparison, veterinary use in farm animals is around 60% below the EU average.
Use of all growth promoters in farm animals was banned in the EU in 2006. This includes low dose antibiotics, which are still used in many countries globally to increase growth rates in animals, and hormones.
For use of antibiotics in animals to be a problem to humans, a number of hurdles have to be overcome. The resistant bacteria have to be on or in the animal to start with. From there, they can be transferred directly to animal handlers. But more commonly they would have to get into milk, meat or eggs, after which they must survive preparation and/or cooking. For example, this is via unpasteurised milk, unhygienic food handling or incorrect cooking. Then they must enter the human – most commonly by eating or drinking. After that, the bacteria need to survive the acid in the stomach before reaching the human intestine.
At this point, they must ‘colonise’ the human, frequently the gut and be able to invade his or her system. Bear in mind that animal isolates do not always colonise humans but often transiently pass through. In the case of Salmonella and Campylobacter, the bacteria in animals are the same as in humans. This means they could- in theory – colonise and cause problems in susceptible people. Escherichia coli and Enterococcus bacteria don’t usually colonise or infect the human directly. However, they may occasionally transfer their resistance to the human-adapted strains of these bugs while passing through the gut. This is a complex sequence of events which rarely happens inside the human gut. Problems can arise if these human strains of bacteria which have acquired antibiotic resistance from animal strains of bacteria then actively infect humans. This can reduce the effectiveness of the antibiotic therapy used to treat the infection.
We find them on almost all surfaces, at work and at home. Studies have found them everywhere from computers keyboards to make-up bags and on public transport. In farming, they are on plants and animals, around large and small farms, in organic and conventional produce, and in pets and horses. This is because resistance develops naturally as bacteria defend themselves against attack from other microbes that produce antibiotics. Resistant bacteria millions of years old have been found in the ice caps and in the frozen remains of woolly mammoths.
This is often suggested in the popular media. But it’s the level of use and misuse of antibiotics that is the major factor – and this is not necessarily linked to farm scale or system. As mentioned above, resistant bacteria are found on conventional and organic farms alike. Some highly productive systems are aiming to become virtually antibiotic-free in the next few years – subject to being able to maintain their high health and welfare standards.
The use of veterinary medicines – including antibiotics – can sometimes result in low concentrations of the medicine being present within the animal’s system for a period of time. This is usually at a low level – measured in parts per million. Strict withdrawal periods are stipulated for each licensed medicine. These are based on rigorous testing regimes, and give time for medicines to be excreted from the animal or fall to a level that will not cause any adverse reaction in man should they be eaten. This means medicines must have almost entirely left the animal body by the time meat or milk can enter the food chain. In summary, the current debate is not about antibiotics found in food, but whether resistant bacteria are found in food and can they be transmitted to man.
Sometimes presented as ‘routine’ use to prevent disease, prophylactic (preventative) treatment is widely debated. It’s clear that the term means different things to different groups. There is, however, a widely held and justifiable belief, by both medics and vets, that controlled intervention to prevent the outbreak and further spread of disease in infected or carrier animals, based on sound professional examination and advice, is better than cure. RUMA and most British veterinary and farming organisations do not support routine preventative use of antibiotics. They confirm it ‘must not be used to compensate for poor hygiene or for inadequate husbandry conditions or where improvements in animal husbandry could reduce the need for antibiotic treatment’.
Far from the way it can be portrayed, oral treatment of groups of animals through their feed (or mass-medication) can be the most effective treatment method. This is especially if given before disease affects their appetite. Catching and injecting individual animals can be very stressful to the animal. Outdoor-reared animals, such as sows or free-range laying hens, drink rainwater in puddles, making application through the drinking water system unreliable and risks under-medication. Large groups of poultry could equally be stressed by catching, especially if a course involving daily treatment is needed. Hence this makes individual treatment impractical. In-feed medication may therefore provide the most practicable option in many cases. It should be up to the vet and the farmer to decide the optimum way to administer medication, which remains under veterinary control or prescription.