This story originally appeared in The guard and is part of Climate Office cooperation.
Urban ducks and crows may give us a sense of connection to nature, but scientists have found that wild birds living near humans are more likely to carry bacteria resistant to essential antibiotics.
Antimicrobial resistance (AMR) is largely caused by the overuse of medicines such as antibiotics by humans and livestock.
The problem is earnest: According to data for 2019approximately 4.95 million deaths worldwide were related to antimicrobial resistance, including 1.27 million directly caused by antimicrobial resistance.
Scientists say that wild bird species that often appear in cities are reservoirs of multidrug-resistant bacteria.
“We’re basically seeing genes that confer resistance to antimicrobials that could be used to treat infections in humans,” said Samuel Sheppard, a co-author of the study from Ineos Oxford Institute for Antimicrobial Research.
The team says their findings are essential because wild birds have the ability to travel considerable distances. Sheppard said a key concern is that these birds could transmit antimicrobial-resistant bacteria to captive birds destined for human consumption — such as those kept on poultry farms.
In a paper published in the journal Current Biology, Sheppard and his colleagues describe how they analyzed the genomes of bacteria found in 700 bird droppings samples from 30 species of wild birds from Canada, Finland, Italy, Lithuania, Japan, Sweden, the United Kingdom and the United States.
The team specifically investigated the presence of different strains Campylobacter jejuni—a genus of bacteria that is ubiquitous in birds as a natural part of the gut microbiome. Such bacteria are a major cause of human gastroenteritis, although antibiotics are usually used only in severe cases.
Sheppard added that in general, each wild bird can be expected to carry one strain. C. jejunispecific to a given species.
However, the team found that wild birds appearing in urban environments have significantly more strains C. jejuni than those that live away from people.
Moreover, strains from urban species contained about three times more antimicrobial resistance genes, and these genes were also associated with resistance to a wider range of antimicrobials.
The authors suggest that wild birds can become infected with antimicrobial-resistant bacteria in several ways: for example, seagulls and crows are known to lurk in landfills, while ducks and geese can infect them in rivers and lakes polluted by human sewage.
Thomas Van Boeckel, an expert on antimicrobial resistance at ETH Zurich who was not involved in the work, said the study was unusual because it focused on the effects of human antimicrobial operate on animals.
“What are the consequences for birds? We don’t really know, but it seems that we, humans, are responsible for this change,” he said.
Danna Gifford, from the University of Manchester, added that the findings could have implications for human health.
“Although this is alarming, the risk of direct transmission of resistance from urban birds to humans is unclear. However, transmission from poultry to humans is well documented,” she said. “As urban development encroaches on agricultural areas, the increasing contact between urban birds and poultry raises serious concerns about indirect transmission through the food chain.”
Andrew Singer, of the UK’s Centre for Ecology and Hydrology, said more samples were needed to be sure the results were reliable but that precautions could be taken.
“The most obvious place to start is to ensure that birds do not congregate in our landfills, sewage treatment plants and animal dumps, where both pathogens and AMR are common,” he said. “Furthermore, we must also eliminate the discharge of untreated sewage into our rivers, which exposes all wildlife that use the rivers — and humans — to pathogens associated with humans and AMR.”