Urban wildlife such as birds and bats may be spreading superbugs around the cities of developing nations and beyond because of poor management of human and animal waste, researchers have warned.
A study in the Lancet Planetary Health journal shows that seed-eating birds, scavenging birds such as storks and fruit bats in Nairobi, Kenya, carry high levels of bacteria such as E. Coli that are resistant to antibiotics.
And if these bugs are passed to migrating birds they could be carried all the way to Europe, one of the authors of the paper said.
While the study does not show that these resistant bacteria have been passed from wildlife to humans the study warns that a superbug could emerge from the “brew” of wildlife, livestock and humans that live cheek by jowl in the sprawling cities of developing nations.
Antimicrobial resistance (AMR) is an increasing global threat, with a recent report from the United Nations warning that if left unchecked it could kill 10 million people by 2050.
Researchers from the University of Liverpool and the International Livestock Research Institute in Nairobi took faeces samples from wildlife, livestock and humans in household compounds across the city – from urban slums to the most affluent areas.
They tested the samples for the presence of E. coli and the prevalence of resistance to 13 different antibiotics.
Of the 2,000 wildlife samples collected, 485 were found to harbour E. coli – and half of these were resistant to more recently developed antibiotics, such as cephalosporins and fluoroquinolone, drugs that the World Health Organization considers crucial for human medicine.
There were higher levels of multi-drug resistant superbugs in both humans and livestock but the researchers say their findings show that wildlife, particularly birds, are an important vehicle for spreading AMR.
In cities birds and bats forage on sewage treatment plants, rubbish dumps and waste from abattoirs, therefore picking up superbugs excreted from both humans and livestock.
Because human and animal waste is poorly managed and livestock live in close proximity to people there is ample opportunity for wildlife to pick up these bugs and then carry them to other areas – including outside the city.
Nairobi National Park, to the south of the Kenyan capital, is home to many birds, including species that migrate to Europe.
Eric Fèvre, professor of veterinary infectious diseases at the University of Liverpool, said the paper showed that contamination of urban environments with AMR is a serious issue and the findings could be applied to any developing nation city where humans and animals live on top of each other.
“We tend to think of AMR in primarily medical terms, of developing new drugs and better using old ones. But we need to take an ecological approach to addressing this threat,” he said.
He added: “The management of the environment in the city is very important - not only for human health but specifically for understanding the development of antibacterial resistance.”
“One of the key messages [of this paper] is that when you design a city you have to consider waste disposal very explicitly,” said Prof Fèvre.
He said that migrating birds could carry the superbugs both to and from Europe.
He said: "It is possible [a bird could carry a bug to the UK]. The reverse is also true of course - a UK or Europe generated superbug, of which there are many, from a hospital, a sewage works or wherever, could be carried by a bird to Nairobi and spread locally there."
James Hassell, lead author of the study, said: “Since wildlife are not treated with antibiotics, this is indicative of how pervasive AMR is in urban environments. Species that move freely across cities and further afield could disseminate resistance acquired in urban areas more widely.”
“As many scientists and policymakers are now realising, we cannot address the rise of antimicrobial resistance without focusing on the environmental, ecological and social settings in which humans exist.”
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