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Scientists have found that wild birds are more likely to carry antibiotic-resistant bacteria if they live near humans, marking the latest warning about the global spread of “superbugs”.
The researchers said that urban-dwelling species, such as ducks, crows, gulls and geese, had up to three times more genetic markers associated with drug resistance than their avian counterparts from more remote locations.
The findings underscore the growing threat of antimicrobial resistance (AMR) to the effectiveness of vital medicines. They further illuminate concerns about the possible transmission of so-called zoonotic diseases between animals and humans, as in the current avian influenza outbreak in the United States.
“There is an urgent need to understand how human activity is influencing the spread of zoonotic diseases and antimicrobial resistance,” said Professor Samuel Sheppard, lead author of the latest research, published Tuesday in the journal Current Biology (Cell Press).
The study highlighted the need for far-reaching global action to limit the spread of AMR, including in the areas of wildlife conservation, public health and agriculture, added Sheppard of the Ineos Oxford Institute and the University of Oxford’s Department of Biology.
An international team of researchers examined 700 samples of bacteria from the guts of 30 species of wild birds in eight countries, five of which were in Europe, Japan, the United States, and Canada. They analyzed the diversity of strains of Campylobacter jejuni, a zoonotic bacterium that causes diarrhea and lives in the intestines of birds.
Species concentrated in urban areas had more genetic markers associated with AMR and a wider range of bacterial strains than their counterparts in more rural settings. The AMR marker genes included some associated with resistance to commonly used antibiotics such as fluoroquinolones, which treat a range of illnesses from pneumonia to urinary tract infections.
The study showed that authorities should consider tougher measures to reduce human exposure, such as ensuring birds do not congregate at landfill sites, sewage treatment plants and animal waste piles, “where both pathogens and antimicrobial resistance are abundant,” said Dr Andrew Singer, principal scientist at the UK Centre for Ecology and Hydrology.
“We also need to eliminate the discharge of untreated sewage into our rivers, which exposes all wildlife that use the rivers, and humans, to human-associated pathogens and antimicrobial resistance,” Singer added.
AMR has been called a “hidden pandemic” because of its global reach. It developed because careless use and disposal of essential medicines allowed bacteria and other pathogens in the wider environment to develop resistance.
Next month, on the sidelines of the United Nations General Assembly, countries will hold talks on how to address antimicrobial resistance.
The latest paper showed how governments need to focus on the fact that “birds are vectors of disease and the spread of gene pools,” said Brendan Wren, professor of microbial pathogenesis at the London School of Hygiene & Tropical Medicine.
“Most of us live in urban environments and we need to think very carefully about our interactions with nature,” Wren said. “Birds have frequent encounters with humans and can rapidly spread their microbiome and associated gene pool because they have few geographic boundaries.”
Katherine Lagerstrom, a rising researcher in the department of ecology and evolutionary biology at Princeton University, said antimicrobial resistance is largely a human-caused problem.
“While it is true that wild migratory birds, and other wildlife, may play a role in the distribution of AMR bacteria, we are largely responsible for the creation and spread of clinically relevant AMR,” said Lagerstrom, who added that the study would have benefited from a larger sample size.
“We are also the main reason why wild birds carry it.”
