Genes capable of creating antibiotic-resistant superbugs have been detected in the UK’s largest lake, which supplies drinking water to around 40% of Northern Ireland.
Tests of water from Lough Neagh, which has an area 26 times the size of Windermere, found genes resistant to a wide range of antibiotics, including carbapenems, drugs reserved for life-threatening infections when all other treatments have failed.
The discovery comes at a time when deaths related to antibiotic-resistant infections are increasing around the world. Almost 400 resistant infections are reported every week in England, and deaths related to them are estimated to reach 2,379 in 2024, according to data from the UK Health Security Agency.
The World Health Organization (WHO) describes this antimicrobial resistance (AMR) as “one of the most urgent, complex and terrifying health challenges of our time.”
Samples taken by Watershed Investigations and The Guardian found resistance genes spanning multiple classes of antibiotics, from common penicillins to last-resort carbapenems, as well as quinolones, macrolides, aminoglycosides and cephalosporins, which are used to treat pneumonia and other serious infections. Genes resistant to tetracycline, widely used in livestock farming, were also present.
“Carbapenems are known as last line of defense antibiotics because they are only used when other treatments have failed,” said Will Gaze, professor of microbiology at the University of Exeter. “If pathogens are resistant to carbapenem antibiotics, they will also be resistant to many others.”
Samples from a designated bathing water area in the lake were also affected. Gaze said: “If a swimmer swallowed 30ml of lake water, they would have pretty good exposure to carbapenem resistance genes, but we don’t know what impact that has on the gut microbiome or infection risk.”
In addition to resistance genes, markers from human, cow and pig feces were detected in the water. Sewage and livestock manure create ideal conditions for superbugs, dumping pathogens, antibiotic residues and resistant bacteria into waterways, where they can mix, multiply and spread.
“Sewage and livestock manure can contain pathogens that can cause serious infections,” Gaze said. “If those organisms carry resistance genes, they are much more difficult to treat.”
Sewage and sludge pollution is widespread across the UK. In Lough Neagh it has caused huge blooms of toxic algae, visible from space, which are choking wildlife and helping to spread antibiotic resistance. Despite several environmental protections, the lake is now in such poor health that activists recently held a mock funeral for it.
Northern Ireland Department of Agriculture, Environment and Rural Affairs (Daera) Minister Andrew Muir said more than 20 million tonnes of raw sewage is dumped into the country’s waterways each year. Around 30% of Northern Ireland Water’s storm overflows discharge raw sewage into Lough Neagh, 106 directly and 618 indirectly via rivers.
But the magnitude of the problem may be even greater. A water industry expert warned that monitors were being installed at water company storm overflows, but not at wastewater treatment plant outfalls, where large volumes can enter waterways unchecked.
“Many more wastewater reaches rivers and lakes than water companies assume,” said the expert. “Forty per cent of Northern Ireland drinks water from a fetid pond full of bacteria from human and animal waste, and now, unsurprisingly, there are antimicrobial resistance genes.”
However, even treated wastewater poses a risk. Davey Jones, professor of environmental sciences and public health at Bangor University, warned: “Just because wastewater is treated does not mean it is safe.”
“(Sewage overflows) are really bad, but they are not always discharged and can be diluted, while AMR genes are pumped through treated wastewater every day.”
He described sewage networks as an “epic breeding ground meganetwork” for resistant microbes and called for better treatment technologies in wastewater plants.
However, the Northern Ireland Fiscal Council, a non-departmental public body, said the company lacked sufficient funding for the scale of wastewater investment required and was forced to prioritize drinking water. As a result, Northern Ireland Water is spending public money trying to clean up pollution caused by its own infrastructure.
A spokesperson for Northern Ireland Water acknowledged “decades of underinvestment”, saying the company had been left “very limited scope to make improvements” and that only a “permanent, sustainable investment plan” would close the long-term funding gap.
Meanwhile, “the consequences are restrictions on development, an increased risk of pollution and worsening pressure on the environment,” they said. “Strict targets” are being introduced to reduce pollution incidents and new monitoring equipment is being installed to track storm overflows in the Lough Neagh catchment, they added.
However, wastewater is only half the story. Livestock manure runs off farmland, fueling algae blooms and dumping antibiotics, pathogens and resistance genes into the lake.
Pressure from agriculture has intensified in recent years. Since a government policy promoting intensive farming was introduced in 2013, pig numbers in Northern Ireland have increased from 517,075 to 744,643, while poultry numbers have increased from approximately 19.5 million to 25.8 million. Currently there are approximately 1.6 million cattle and 1.8 million sheep in the country.
Jones described livestock as “pathogen bioreactors on four legs,” arguing that streams should be fenced to prevent animals from defecating directly into waterways, and that farmers should stop spreading slurry at the wrong time of year. “I’ve seen people do it because their sludge tanks are full and they have to get rid of that stuff,” he said.
A recent study found my coli in each livestock manure sample analyzed.
Progress has also been hampered by governance failures. The Environmental Protection Office found that Northern Ireland lacked an environmental regulator free from government influence.
A Daera source described the collapse of morale within the Northern Ireland Environment Agency. “They are not allowed to talk, to breathe, to do their job. They are not supposed to prosecute agriculture or take Northern Ireland Water to court, even though so many wastewater works are beyond their capacity.”
Northern Ireland Water has largely avoided prosecution since 2007, when an agreement was signed limiting regulators’ ability to pursue the company, although Muir withdrew that agreement on March 3 this year.
Muir also attempted to establish an independent environmental regulator, but the proposal was blocked at Stormont by the Democratic Unionist Party (DUP). The Daera source alleged that agriculture had significant political influence, and that many farmers were part of the DUP’s support base.
“Antimicrobial resistance is an urgent global challenge and evidence has been found in the aquatic environments of Northern Ireland, including Lough Neagh,” Muir said, adding there were plans for further testing. “The restoration and protection of the ecological health of Lough Neagh cannot be underestimated and work is underway on the Lough Neagh Action Plan.”
The overuse of antibiotics in both people and livestock supports the rise of resistance.
In a bid to address it, the UK government is aiming to reduce its use in humans by 5% by 2029 from a 2019 base. NHS antibiotic prescribing fell slightly between 2019 and 2024, but private prescribing more than doubled over the same period, pushing overall primary care use up to 10.7%, and 22% of all antibiotics are now dispensed privately. Northern Ireland has the highest rate of antimicrobial prescribing in the UK.
Ruth Chambers, a member of the Green Alliance think tank, said the situation had “all the ingredients to be a perfect storm for the health of the people and environment of Northern Ireland” and called for the creation of an independent environmental protection agency to be accelerated.
Natalie Sims, policy adviser at the Royal Society of Chemistry, warned that the UK risks falling behind the EU, which is introducing laws requiring countries to monitor antimicrobial resistance in wastewater. “We still understand very little about how the aquatic environment contributes to the spread of antimicrobial resistance,” he said. “Without solid environmental data, we risk missing an important part of the problem.”
Without urgent action, the WHO warns, drug-resistant infections could claim 39 million lives worldwide by 2050 and impose an annual economic burden of up to $412 billion (£307 billion).
