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A study published in Current Biology looks at wild birds and antimicrobial resistant bacteria in cities.
Dr Andrew Singer, Principal Scientist at the UK Centre for Ecology & Hydrology, said:
“The authors appear to focus on the relationship of some birds and their proximity to humans and AMR in preference to other birds where there appears to not be any AMR found. It’s not clear whether the relationship proposed by the authors would hold up to statistical scrutiny if many more samples were acquired. One can imagine that the act of capturing a sample will be fraught with challenges that MIGHT impact on the results in a material way. As such, more samples means more confidence in the data.
“However, this paper does make an important first effort towards suggesting a relationship between the proximity of birds’ habitat to humans and AMR, which intuitively feels like a justifiable hypothesis to propose. The implications of such a positive relationship might mean that just as humans impact the AMR carriage of birds exposed to our waste, we might find ourselves as ‘sinks’ for the pathogens and resistance genes found within the bird waste to which we are exposed.
“The precautionary principle might apply here, which would endeavour us to pollute our environment less to minimise the risk of wild animals, such as birds, from acting as both a sink and source for these pathogens and antibiotic resistance genes, in the future. The most obvious place to start is to ensure birds do not congregate in our landfills, wastewater treatment plants, and animal muck piles where both pathogens and AMR are abundant; 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.”
Prof Brendan Wren, Professor of Microbial Pathogenesis at the London School of Hygiene & Tropical Medicine, said:
“Most of us live in urban environments and we must consider our interactions with nature very closely. Birds have frequent encounters with humans and can spread their microbiome and associated gene-pool rapidly as they have few geographic boundaries. This study elegantly demonstrates an association that birds found in an urban environment are more likely to carry antibiotic resistance genes and the human gut pathogen Campylobacter jejuni. This bacterium happily exists in bird guts but doesn’t survive well in the natural atmosphere, yet counterintuitively is the leading cause of bacterial food poisoning worldwide. Clearly urban birds are important for human disease transmission and for harbouring antimicrobial resistance genes.
“In my opinion, this is an important study in an under-appreciated area. The bioinformatics approaches and analyses are solid and use more than one line of evidence. Ideally the number of samples from non-urban birds, e.g. in Antarctica, could be higher – but to some extent, this study confirms what we already suspected. Governments need a better appreciation that birds are vectors of disease and spreading gene-pools.”
Dr Ozan Gundogdu, Associate Professor in Infection Biology at the London School of Hygiene & Tropical Medicine, said:
“This research is timely given the importance of antimicrobial resistance. With globalisation, urbanisation and the intensification of food production systems, the study of pathogen transmission between animals and humans, and the impact on antimicrobial resistance will be crucial in us implementing novel intervention and control strategies.”
Dr Katherine Lagerstrom, Incoming Postdoctoral Researcher at Princeton University Department of Ecology and Evolutionary Biology, said:
“Studies investigating the transmission of pathogens between human and animal populations, including and perhaps especially those with the added risk of being or becoming antibiotic-resistant, are incredibly important for both human and animal health. While it’s true that wild migratory birds – and other wild animals – may play roles in distributing AMR bacteria, we are the primary reason they carry it. If such pathogens also harm wildlife health, they could compound the already extreme and ongoing loss of biodiversity globally. We need to insure we do not lose sight of our role in creating these problems in the first place and resist the temptation to cast the blame on wildlife, who only harbor AMR bacteria as a collateral consequence of our extensive use of antibiotics.
“Action items for us include:
“Numerous other studies have reported finding clinically relevant AMR bacteria in wild birds proximal to urbanization. The present study compliments those findings by developing a statistical method for estimating a bird’s proximity to urban areas. Indeed, it has been suggested that wild bird populations serve as indicators of the extent of human impact on the environment.
“One note of caution in the interpretation of analyses like these is that the identification of known resistance genes in genomic data does not always correspond to phenotypic resistance, i.e., the presence of a specific AMR gene does not necessarily translate to that bacterium being resistant to said antibiotic in an infected individual. Another limitation, which was mentioned in this study, is the low sample sizes from half the countries included. For example, just 8 birds were sampled from Japan, 3 from Sweden, 1 from Lithuania, and 1 from Canada. They did mention an attempt to account for this under-sampling in their methods, however I don’t believe one can ever compensate completely for relying on 1 individual bird to represent an entire country.”
‘Proximity to humans is associated with antimicrobial resistant enteric pathogens in wild bird microbiomes’ by Evangelos Mourkas et al. was published in Current Biology at 4pm UK time on Tuesday 13 August 2024.
Declared interests
Brendan Wren: I have no competing interests
Katherine Lagerstrom: I have no declaration or conflict of interests except that I recently joined the One Health Advisory Group of AMI and was just elected to their Board of Trustees (this July).
For all other experts, no reply to our request for DOIs was received.