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Wild birds are more likely to be carriers of antibiotic-resistant bacteria if they live close to humans, scientists have discovered, marking the latest warning about the global spread of “superbugs”.
Urban-dwelling species such as ducks and crows had up to three times as many genetic markers associated with drug resistance as their avian counterparts from more remote places, researchers said.
The findings underscore the growing threat of anti-microbial 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, such as in the current bird flu outbreak in the US.
“There is an urgent need to understand how human activity is influencing the spread of zoonotic diseases and AMR,” said Prof Samuel Sheppard, lead author of the latest research, which was published in the journal Current Biology (Cell Press) on Tuesday.
The study highlighted the need for wide-ranging global action to limit AMR’s advance, including in the areas of wildlife conservation, public health and agriculture, added Sheppard, of the Ineos Oxford Institute and Oxford university’s biology department.
An international group of researchers examined 700 samples of bacteria taken from the guts of 30 wildfowl species across eight countries — five in Europe, Japan, the US and Canada. They analysed the diversity of strains of Campylobactor jejuni, a diarrhoea-causing zoonotic bacteria that lives in birds’ guts.
Species concentrated in urban areas had more genetic markers associated with AMR and a wider range of bacterial strains than 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 diseases from pneumonia to urinary tract infections.
The study showed that authorities should consider tougher measures to reduce humans’ exposure, such as ensuring birds did not congregate in refuse landfills, wastewater treatment plants and animal waste piles “where both pathogens and AMR are abundant”, said Dr Andrew Singer, principal scientist at the UK Centre for Ecology & Hydrology.
“Moreover, we must also eliminate the discharge of untreated sewage into our rivers, which exposes all river-using wildlife — and humans — to human-associated pathogens and AMR,” added Singer.
AMR has been dubbed a “hidden pandemic” due to its global scope. It has developed because the careless use and disposal of crucial medicines has enabled bacteria and other pathogens in the wider environment to build resistance.
Countries are due to hold talks on the margins of the UN general assembly next month on how to deal with AMR.
The latest paper showed how governments needed to focus on how “birds are vectors of disease and spreading 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 must consider our interactions with nature very closely,” Wren said. “Birds have frequent encounters with humans and can spread their microbiome and associated gene-pool rapidly as they have few geographic boundaries.”
Katherine Lagerstrom, an incoming researcher at Princeton University’s department of ecology and evolutionary biology, said AMR was principally a human-generated problem.
“While it’s true that wild migratory birds — and other wild animals — may play roles in distributing AMR bacteria, we are the most responsible for creating and spreading clinically relevant AMR,” said Lagerstrom, who added the study would have benefited from larger sample size.
“We are also the primary reason wild birds carry it in the first place.”
