Feeding of white storks on landfills could make these vectors for the dispersal of antibiotic resistant bacteria

    A multidisciplinary team of researchers reveals that, when foraging on landfills, White storks acquire multiresistant strains of the common bacteria Escherichia coli, and could disperse these over long distances.


    When we use antibiotics excessively, be it in human or veterinary medicine, residues of antibiotics that reach the ecosystem are considered contaminants. They can remain biologically active over large periods of time both in terrestrial and aquatic habitats causing the evolution of antibiotic resistant bacteria.

    Currently these multiresistant bacteria that have acquired resistance against most of the existing antibiotics are considered one of the direst threats to human, livestock and environmental health, already being responsible for more than 30,000 deaths in the EU and more than 700,000 globally.

    Recent studies have suggested that wildlife could have a significant role in the dispersal of antibiotic resistant bacteria in the environment, even between ecosystems located far apart. The species more directly implicated in this undesirable process of dispersal are generally species that like White storks (Ciconia ciconia) forage for food in locations where these bacteria can be especially abundant, such as urban solid residue landfills or in areas with intensive livestock grazing.

    White storks (Ciconia ciconia) can become exposed to antibiotic resistant bacteria when they forage on landfills or where high qunatities of livestock faeces are present. Due to their migratory behaviour they could spread multiresistant bacteria over long distances (Photo: Holger Schulz/“SOS Storch” Project).

    On the other hand, as wildlife is not generally treated with antibiotics, the White stork could be an excellent “sentinel species” that could help to detect the presence of antibiotic resistant bacteria in the environment.

    It is crucial to understand how antibiotic resistance is dispersed , if we want to reduce and prevent problems caused by multirresistant bacteria. The stakes are high as these multiresistant organisms could cause millions of deaths due to minor infections that currently are easily cured.

    Such was the objective of a multidisciplinary team of scientists born from the collaboration between the Research Group in Health and Biotechnology (SaBio) of the Instituto de Investigación en Recursos Cinegéticos (IREC – CSIC, UCLM, JCCM) and the Centro de Investigación en Sanidad Animal (CReSA) from the Instituto de Investigación y Tecnología Agroalimentaria (IRTA-UAB), with the participation of researchers from the Vall d’Hebron Hospital, SEO/BirdLife, the Doñana biological research station (EBD-CSIC) and the Universidad Complutense de Madrid (UCM).

    The scientists took samples from more than 460 White storks from 12 different colonies in 5 different regions throughout Spain. In addition, they collected 70 recently deposited droppings below nesting platforms. In all these samples they analyzed the presence of muliresistant isolates of Escherichia coli as well as genes coding for antibiotic resistance and identified risk factors leading to the acquisition of both.

    The results of the study reveal that White storks that feed on urban household residue landfills are contaminated by multiresistant strains of bacteria such as E. coli, a fecal commensal bacteria that when consumed with contaminated water or food can lead to serious infections in humans. In addition, the storks can disperse multiresistant strains of E. Coli over long distances, at least 250 km or more.

    In contrast, multirresistant bacteria do not seem to persist in the intestinal environment of the storks and cannot be detected in consecutive seasons, thus making White storks ideal sentinels for the detection of the presence of multiresistant bacteria in an area.

    These results provide new evidence for the risks posed by the interface of wildlife and humanized habitats. In the light of this data it would be advisable to limit the access of wild birds to residues of urban households as contemplated in the European waste management plan. On the other hand, precisely wild birds foraging in these areas such as White storks could be used as sentinels to follow the success of measures against the dispersal of antibiotic resistance into the environment.

    On the other hand, this information is especially relevant now in the context of the current Covid-19 pandemic, as the hospitalization of many critically ill patients increases the need for the use of antibiotics to combat secondary infections leading to the release of a much higher amount of residues of antibiotics of medical use into the environment.

    The scientific publication of this research is available at:

    Höfle, U., Gonzalez-Lopez, JJ, Camacho, MC, Solà-Ginés, M., Moreno-Mingorance, A., Hernández, JM, De la Puente, J., Pineda-Pampliega, J., Aguirre, JI , Torres-Medina, F., Ramis, A., Majó, N., Blas, J., Migura-Garcia, L. 2020. Foraging at Solid Urban Waste Disposal Sites as Risk Factor for Cephalosporin and Colistin Resistant Escherichia coli Carriage in White Storks (Ciconia ciconia). Frontiers in Microbiology 11, 1397.