Seagulls act as sentinels of antibiotic-resistant bacteria in urban environments

A new study led by the Institut de Ciències del Mar (ICM-CSIC) and the Barcelona Public Health Agency (ASPB) has revealed that urban gulls can spread zoonotic and antibiotic-resistant bacteria in urban environments. In addition to analyzing the presence of these pathogens in yellow-legged gulls (Larus michahellis), the movements of these animals have been monitored to identify the distances they travel and the areas they visit most often. Although the risk of transmission is low, the study concludes that the results of the research provide key data for public health management in these environments.

Specifically, the study, published in Science of the Total Environment, evaluates the presence of pathogenic bacteria in yellow-legged gulls living in Barcelona. To carry out the work, a total of 129 individuals were captured and analyzed in the ASPB laboratories. Results show the presence of antibiotic-resistant Escherichia coli in 14% of the gulls sampled and a low prevalence of Campylobacter jejuni and Listeria monocytogenes. It should also be noted that neither Yersinia enterocolitica nor Salmonella spp. were detected during the analyses. All of these bacteria can have health implications for people.

On the other hand, researchers studied the movements of the captured seagulls using GPS devices. This allowed them to generate maps of potential dispersion of pathogens by urban gulls and to identify the type of facilities most sensitive to the presence of these pathogens, such as primary care centers, hospitals, food establishments and industries, schools or ornamental fountains.

"Combining seagull movement data with pathogen analysis allows us to generate explicit maps that can be fundamental for public health management in large cities such as Barcelona," states Víctor Martín-Vélez, postdoctoral researcher at the ICM-CSIC. 

Another relevant conclusion of the study is that immature gulls can disperse pathogens over much greater distances than adults. Thus, while the former can travel up to 167 kilometers, the latter reaches, on average, 53 kilometers. On the other hand, the results of the study show that ornamental fountains in first place, and school facilities in second place, are the spaces most visited by seagulls in urban areas.

Given this scenario, Tomás Montalvo, ASPB researcher, points out that "the identification of areas sensitive to the dispersion of pathogens by seagulls provides evidence for coordination with land managers to implement measures to reduce potential risks, as is already happening in the case of ornamental fountains in Barcelona".

Finally, in this sense, the ICM-CSIC researcher Joan Navarro indicates that "understanding the interactions between the environment, wildlife, and humans is essential to prevent the spread of pathogens within the One Health perspective", which brings to the table the value of studies with a multidisciplinary approach such as this one.