UK pig farms’ increasing use of a class of antibiotics critically important for human health has prompted concerns about farming practices and efforts to reduce reliance on the drugs. Previously unpublished industry data seen by the Guardian, the Bureau of Investigative Journalism and Vet Record shows the use of a class of antibiotics prescribed for various infections in humans more than doubled on UK pig farms between 2015 and 2019. According to the investigation the drugs are being administered on farms supplying pork to Tesco and Waitrose, which both insisted they are used responsibly. Farmers have been cutting back on antibiotic use in recent years, with the amount prescribed to treat pigs in the UK falling by 62% since 2015. But according to the data there has been an increase over the same period in the use of aminoglycosides, a class of drugs that includes gentamicin, which is used in humans to treat meningitis and infections of the blood and abdomen. Aminoglycosides are deemed “critically important” to human health by the World Health Organization, but are used on pig farms to combat scour [diarrhoea] and other illnesses. Data compiled by the Agriculture and Horticulture Development Board, released after a freedom of information request, shows the use of aminoglycosides in pigs increased from 2.6mg a kilogram of body weight in 2015 to 5.9mg in 2019. In 2018, the European Medicines Agency warned that “the use of [aminoglycosides] in human and veterinary medicine is associated with the increased prevalence of resistance”, citing examples of drug-resistant E coli, salmonella and livestock variants of MRSA (methicillin-resistant Staphylococcus aureus). However, the UK follows the European Medicines Agency categorisation for veterinary antibiotics, which classifies aminoglycosides below the highest priority antibiotics. According to industry experts, the recent jump in the use of aminoglycosides is probably due to the phasing out of antibiotics such as colistin, classified as a higher priority for human health, and changes on farms preparing for a ban across the EU and UK on the use of zinc oxide from next year, also commonly used to control scour. “While use of colistin to treat post-weaning diarrhoea in pigs across a number of different weaning and rearing systems continues in some parts of Europe, in the UK, affected pigs have instead been treated with zinc oxide or lower priority antibiotics like aminoglycosides,” said Paul Thompson, a vet and president of the Pig Veterinary Society. Many farmers had been preparing for the zinc ban by trialling alternative systems, said Thompson, but “not all of these have been successful which will have resulted in more antibiotic use in some cases as sick animals have needed treatment for welfare reasons”, he added. Simon Doherty, a past president of the British Veterinary Association, said: “In the short term, we might have to accept that part of the refinement in a move away from zinc oxide or from colistin is that there will be an increase in the use of, for example, aminoglycosides.” Responding to the findings, Cóilín Nunan, scientific adviser at campaign group Alliance to Save our Antibiotics, said reductions in antibiotic use could be achieved “if pigs are kept less intensively and husbandry is improved”. He said farms should not be permitted to take piglets away from sows at an early age, which he described as a “stressful practice associated with large increases in antibiotic use”. Thompson said trials are being run by feed companies on altering dietary components to reduce the risk of scour and the subsequent need to treat these animals with antibiotics. A National Pig Association spokesperson said the industry had seen a reduction in the use of the highest priority critically important antibiotics for human health. “We expect usage of different types of antibiotics to vary year on year because vets will prescribe the most appropriate medicine in response to the type of disease which needs to be treated – this is a responsible approach to antibiotic use and the health and welfare of pigs.” The Department for Environment, Food and Rural Affairs said: “It remains our position that the livestock industry should be working towards preparing for the ban on use of zinc oxide as a medicine. While there has been a slight increase in the use of aminoglycosides for pigs, there is no evidence of a link to preparations for the ban.” Jim O’Neill, who chaired the government’s review into superbugs, told the Guardian that the Covid-19 pandemic had underlined the need to put drug-resistant bacteria back on the global political agenda. “There needs to be much stronger international agreement, and discipline following those agreements, that we will dramatically reduce the use of antibiotics in animals – especially those that are critical for human health,” he said. The headline on this article was amended on 17 June 2021 to clarify that it was a particular class of antibiotics that saw a doubling in use.