Antibiotics have colonised the world's rivers and are thought to be fuelling the growing global problem of antimicrobial resistance, according to the first worldwide study of its kind.

Describing the findings as "eye-opening and worrying", academics warned that urgent action must be taken against the "global concern" of superbugs.

Researchers from the University of York, which led the study, found that rivers tested in Africa and Asia frequently exceeded safe limits of antibiotics.

The findings were particularly alarming in Bangladesh, where levels of metronidazole – used to treat a range of common conditions – are up to 300 times higher than recommended.

However the report also found that sites in Europe, North America and South America have high levels of contamination.

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The presence of antibiotics within rivers can cause the spread of antimicrobial resistant infections. Bacteria can react with diluted antibiotics, developing a resistance to life-saving medicines and making infections much more difficult to treat.

Superbugs are already responsible for about 700,000 deaths globally each year, but it is estimated that this number could rise to 10 million people by 2050 if the threat is not addressed.

The study is the first to analyse rivers outside of Europe and North America.

Researchers examined the presence of 14 commonly used antibiotics in rivers in 72 countries, including the Danube, Mekong, Seine, Thames, Tigris and the Chao Phraya.

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According to the report, 65 per cent of rivers sampled contained antibiotics.

The most prevalent antibiotic was found to be trimethroprim, detected at 307 out of 711 sites. It is most commonly used to treat urinary tract infections.

Ciprofloxacin, typically used to treat respiratory tract and skin infections, was the antibiotic found to most regularly exceed safety levels – passing the recommended safe level in 51 rivers.

The report discovered that rivers had become colonised by antibiotics for two main reasons.

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Firstly, the improper disposal of medical waste products by hospitals and manufacturing centres has caused antibiotics to enter bodies of water, particularly in areas where sewage dumps were adjacent to rivers.

Secondly, intensive use within animal husbandry has caused antibiotics to wash into rivers through waste.

“The results are quite eye-opening and worrying, demonstrating the widespread contamination of river systems around the world with antibiotic compounds,” said Professor Alistair Boxall of the York Environmental Sustainability Institute.

“Solving the problem is going to be a mammoth challenge and will need investment in infrastructure for waste and wastewater treatment, tighter regulation and the cleaning up of already contaminated sites.”

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