Intensive farming of livestock is helping to drive antibiotic resistance in bacteria, which could be disastrous to human health, according to a new report. Published by the Review on Antimicrobial Resistance, it details how the extensive use of the drugs in animals around the world could be pushing us into a post-antibiotic era, when all the drugs known to fight the most common infections might become useless. The authors lay out the drivers for the overuse of antibiotics, and what needs to be done to prevent it.
The report, commissioned by the British government, details the use of antibiotics around the world, and what the scientific literature says about the dangers of it. It highlights how more of the drugs are used on animals than they are on humans. In the U.S. alone, around 8,900 tonnes, more than 70 percent, of all antibiotics are consumed by livestock, while less than 30 percent are given to humans. The review of 139 academic studies looking at the impact of this unbalance found that only 15 argued against limiting the use of antibiotics on livestock.
Antibiotics are used in agriculture in two separate ways, and normally in an intensive farming setting. The first is as a prophylactic, protecting the animals from getting disease in the first place, as when the animals are in crowded sheds infection can spread rapidly. The second use for the drugs, however, is not to treat animals when they are sick, but to help them gain weight quicker. It is this use that is of particular concern, because they aren’t even being used to improve the health of the animals in question, simply to increase profit for the producer.
The threat of giving antibiotics to livestock was brought to the world's attention earlier this year, when researchers in China found that bacteria in pigs carried a gene which made them resistant to a class of antibiotics called polymyxins. This has caused great concern, as the class was thought to be the only one left in the world that bacteria were not resistant to. Not only that, but the gene was found on structures in the bacteria called plasmids, which enable the resistance to be passed between different species.
“It has long been argued that antimicrobials that are used in human medicine should not be used in animals,” explained Laura Piddock, Professor of Microbiology at the University of Birmingham, who was not involved in the report. “This new report shows that the use of antimicrobials in animals and environmental contamination by waste is a significant driver of global levels of drug resistance.”
The researchers settled on three main recommendations to try and ease the dire situation. The first is to agree a limit on the amount of antibiotics used for animals, which will be followed around the world. They suggest that we follow the model used in Denmark that limits drug use to 50 milligrams per kilogram of meat. To put this in context, the average for the U.S. is almost 200 milligrams per kilogram, and in Cyprus it’s a staggering 425 milligrams. In addition to this, they say that antibiotics used for humans should not be used for animals at all, and finally that we need to improve waste management in antibacterial production.