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Long-term serologic surveillance of red-legged partridges suggests emergence of Bagaza virus in Portugal in 2021, associated with disease outbreaks in this species. Results also reveal sporadic circulation of Usutu virus and endemic circulation of West Nile virus, highlighting the role of red-legged partridges in the transmission and maintenance cycle and as sentinels of orthoflaviviruses.

Telomere length (TL) and shortening is increasingly shown to predict variation in survival and lifespan, raising the question of what causes variation in these traits. Oxidative stress is well known to accelerate telomere attrition in vitro, but its importance in vivo is largely hypothetical. We tested this hypothesis experimentally by supplementing white stork (Ciconia ciconia) chicks with antioxidants. Individuals received either a control treatment, or a supply of tocopherol (vitamin E) and selenium, which both have antioxidant properties. The antioxidant treatment increased the concentration of tocopherol for up to two weeks after treatment but did not affect growth. Using the telomere restriction fragment technique, we evaluated erythrocyte TL and its dynamics. Telomeres shortened significantly over the 21 days between the baseline and final sample, independent of sex, mass, size and hatching order. The antioxidant treatment significantly mitigated shortening rate of average TL (−31% in shorter telomeres; percentiles 10th, 20th and 30th). Thus, our results support the hypothesis that oxidative stress shortens telomeres in vivo.

Antimicrobial resistance (AMR), particularly due to extended-spectrum β-lactamases (ESBLs) and carbapenemases (CPs), poses a critical threat to global health. This study aimed to characterize the molecular epidemiology, resistance profiles, and genomic features of ESBL- and CP-producing Escherichia coli and Klebsiella pneumonaie (ESBL/CP-Ec/Kp) isolates from a Spanish hospital (2020–2024) and explore links to environmental reservoirs like white storks foraging at a nearby landfill. A total of 121 clinical Ec/Kp isolates (55 ESBL-Ec, 1 CP-Ec, 35 ESBL-Kp, 17 CP-Kp, 13 ESBL+CP-Kp) underwent phenotypic testing, PCR, and whole-genome sequencing (WGS). Analyses included phylogenomics (cgMLST), detection of AMR genes, plasmid typing, and comparative genomics. Among ESBL-Ec, blaCTX-M-15 was the most prevalent (60.0%), and one CP-Ec carrying blaNDM-5 was identified. WGS of 44 selected ESBL/CP-Ec isolates revealed a variety of AMR genes, and 56.8% of isolates carried class one integrons (56.8%). IncF-type plasmids predominated, and 84.1% of isolates were assigned as ExPEC/UPEC. The lineage ST131 dominated (75%), with IncF-blaCTX-M-15-carrying plasmids. Among the 18 ESBL/CP-Kp isolates sequenced, the lineage ST307 was the most frequent (44.4%), followed by ST15 and ST11, carrying a diversity of AMR determinants and plasmids (IncFIB(K), IncL, ColpVC). Virulence included ybt loci in ICEKp; hypervirulence genes were absent. Genomic analysis of 62 clinical isolates (44 Ec, 18 Kp) showed close phylogenetic links to stork-derived strains, with ST131-Ec and ST307-Kp from humans and birds differing just by ≤22 and ≤10 ADs, respectively, with a conserved plasmid content (i.e., IncL-blaOXA-48, IncFIB(K)-blaCTX-M-15). High-risk ESBL/CP-Ec/Kp clones persist across clinical and environmental contexts. WGS-based surveillance is key for understanding AMR spread and guiding interventions. Results support a One Health approach to combat AMR through cross-sector collaboration.

Antimicrobial resistance (AMR) represents a threat to human, animal, and environmental health. This study evaluated the potential role of birds as AMR dispersers in white storks as a model species investigating dispersal between locations connected by their movements. Throughout a year, 346 samples were collected from two landfills (225 fecal samples) and two wetlands (93 fecal/28 water samples) based on satellite tracking data that confirmed continuous stork movements between foraging (landfill) and nighttime roosting (wetlands) locations. Samples were seeded in selective media with antibiotics for the isolation of antibiotic-resistant bacteria. A total of 313 isolates from 35 different bacterial species were obtained, with an AMR prevalence of 43.1% in fecal samples from landfills, 7.5% in fecal samples from wetlands, and 21.4% in water from wetlands. Multidrug resistant bacteria were only found in fecal samples (19.6% landfills/4.3% wetlands) and extended-spectrum beta-lactamase producing-bacteria were found exclusively in fecal samples from landfills with a marked presence during the fall migration period. Our study reveals marked differences in AMR prevalence and resistance phenotypes between study locations and fecal and water samples throughout the year, thus not supporting a clear role of storks as AMR dispersers. Nevertheless, similar changes in AMR phenotype prevalences during fall migration in stork faecal samples from one of the tested landfills and its paired wetland, and the significant increase in ESBL-producing Enterobacterales prevalence matching the arrival of migratory white storks in fall, underline the need for more in-depth genome-based studies to elucidate the role of white storks as dispersers or sentinels of AMR.

Bagaza virus emerged in Spain in 2010 and was not reported in other countries in Europe until 2021, when the virus was detected by molecular methods in a corn bunting and several red-legged partridges in Portugal. Sequencing revealed high similarity between the 2021 strains from Portugal and the 2010 strains from Spain.

During 2007–2009 and 2012–2014, avian influenza virus (AIV) was studied in a wild avian community of a northern Spanish wetland using non-invasive sampling methods and host identification by COI barcoding. The aim of this longitudinal study was to evaluate AIV dynamics in a natural wetland ecosystem, taking into account both virological aspects and ecological traits of hosts. Global AIV prevalence decreased significantly during the second sampling period (0.3%) compared to the first (6.6%). Circulating subtype distributions were also different between periods, with a noteworthy H5 and H7 subtype richness during the first sampling period. Mallard Anas platyrhynchos was identified as the main AIV host, although not all positive samples could be ascribed to the host. We modelled AIV prevalence with regard to the avian host community composition and meteorological data from the wetland. Statistical analysis revealed seasonal differences in AIV detection, with higher prevalence during the breeding season compared to other phenological events. The model also shows that the lower AIV prevalence during the second study period was associated with a significant reduction of breeding Anseriformes in the wetland, revealing a long-term fluctuation of AIV prevalence driven by the breeding Anseriformes community. This longitudinal study on AIV epidemiology in a natural ecosystem reveals that although prevalence follows seasonal and annual patterns, long-term prevalence fluctuation is linked to the breeding community composition and size. These results are relevant to understanding the influence of host ecology on pathogen transmission for preventing and managing influenza emergence.

Background Connections between habitats are key to a full understanding of anthropic impacts on ecosystems. Freshwater habitats are especially biodiverse, yet depend on exchange with terrestrial habitats. White storks ( Ciconia ciconia ) are widespread opportunists that often forage in landfills and then visit wetlands, among other habitats. It is well known that white storks ingest contaminants at landfills (such as plastics and antibiotic resistant bacteria), which can be then deposited in other habitats through their faeces and regurgitated pellets. Methods We characterized the role of white storks in habitat connectivity by analyzing GPS data from populations breeding in Germany and wintering from Spain to Morocco. We overlaid GPS tracks on a land-use surface to construct a spatially-explicit network in which nodes were sites, and links were direct flights. We then calculated centrality metrics, identified spatial modules, and quantified overall connections between habitat types. For regional networks in southern Spain and northern Morocco, we built Exponential Random Graph Models (ERGMs) to explain network topologies as a response to node habitat. Results For Spain and Morocco combined, we built a directed spatial network with 114 nodes and 370 valued links. Landfills were the habitat type most connected to others, as measured by direct flights. The relevance of landfills was confirmed in both ERGMs, with significant positive effects of this habitat as a source of flights. In the ERGM for southern Spain, we found significant positive effects of rice fields and salines (solar saltworks) as sinks for flights. By contrast, in the ERGM for northern Morocco, we found a significant positive effect of marshes as a sink for flights. Conclusions These results illustrate how white storks connect landfills with terrestrial and aquatic habitats, some of which are managed for food production. We identified specific interconnected habitat patches across Spain and Morocco that could be used for further studies on biovectoring of pollutants, pathogens and other propagules.

This study determined the carriage rates and antimicrobial resistance (AMR) genes of enterococci from nasotracheal samples of three healthy animal species and in-contact humans. Nasal samples were collected from 27 dog-owning households (34 dogs, 41 humans) and 4 pig-farms (40 pigs, 10 pig-farmers), and they were processed for enterococci recovery (MALDI-TOF–MS identification). Also, a collection of 144 enterococci previously recovered of tracheal/nasal samples from 87 white stork nestlings were characterized. The AMR phenotypes were determined in all enterococci and AMR genes were studied by PCR/sequencing. MultiLocus-Sequence-Typing was performed for selected isolates. About 72.5% and 60% of the pigs and pig-farmers, and 29.4% and 4.9%, of healthy dogs and owners were enterococci nasal carriers, respectively. In storks, 43.5% of tracheal and 69.2% of nasal samples had enterococci carriages. Enterococci carrying multidrug-resistance phenotype was identified in 72.5%/40.0%/50.0%/23.5%/1.1% of pigs/pig-farmers/dogs/dogs’ owners/storks, respectively. Of special relevance was the detection of linezolid-resistant enterococci (LRE) in (a) 33.3% of pigs ( E. faecalis -carrying optrA and/or cfrD of ST59, ST330 or ST474 lineages; E. casseliflavus -carrying optrA and cfrD ); (b) 10% of pig farmers ( E. faecalis -ST330-carrying optrA ); (c) 2.9% of dogs ( E. faecalis- ST585-carrying optrA ); and (d) 1.7% of storks ( E. faecium -ST1736-carrying poxtA ). The fexA gene was found in all optrA -positive E. faecalis and E. casseliflavus isolates, while fexB was detected in the poxtA- positive E. faecium isolate. The enterococci diversity and AMR rates from the four hosts reflect differences in antimicrobial selection pressure. The detection of LRE carrying acquired and transferable genes in all the hosts emphasizes the need to monitor LRE using a One-Health approach.

The molecular ecology of Staphylococcus aureus in migratory birds (such as white storks) is necessary to understand their relevance in the “One Health” ecosystems. This study determined the nasotracheal carriage rates of S. aureus from white storks in Southern Spain and genetically characterized the within-host diversity. A collection of 67 S. aureus strains, previously obtained from 87 white stork nestlings (52 nasal and 85 tracheal samples) fed by their parents with food foraged in natural and landfill habitats, were tested for their antimicrobial resistance (AMR) phenotypes. Moreover, the AMR genotypes, immune evasion cluster (IEC), virulence genes and the detection of CC398 lineage were studied by PCR. The spa types and multilocus-sequencing-typing (MLST) were also determined by PCR and sequencing. Staphylococcus aureus carriage was found in 31% of storks (36.5%/11.9% in nasal/tracheal samples). All isolates were methicillin-susceptible (MSSA) and 8.8% of them were also susceptible to all tested antibiotics. The AMR phenotype/percentage/genes detected were as follows: penicillin/79.1%/ blaZ ; erythromycin-clindamycin-inducible/19.1%/ ermA, ermT ; tetracycline/11.9%/ tetK ; clindamycin/4.5%/ lnuA and ciprofloxacin/4.5%. Twenty-one different spa types, including 2 new ones (t7778-ST15-CC15 and t18009-ST26-CC25), were detected and ascribed to 11 clonal complexes (CCs). MSSA-CC398 (8.2%), MSSA-CC15 (7.1%) and MSSA-ST291 (5.9%) were the most prevalent lineages in storks. Moreover, tst -positive (MSSA-CC22-t223 and MSSA-CC30-t1654), eta- positive (MSSA-CC9-t209) and etb -positive strains (MSSA-CC45-t015) were detected in four storks. The 18.5% of storks harboured distinct MSSA strains (with different lineages and/or AMR genes). Nestlings of storks foraging in landfills (10 CCs) had more diverse S. aureus strains than those of parents foraging in natural habitats (3 CCs). Low level of AMR was demonstrated among S. aureus strains. The predominance of MSSA-CC398 (an emergent clade) and toxigenic MSSA strains in stork nestlings highlight the need for continuous surveillance of S. aureus in wild birds.

Wild birds are considered reservoirs of poultry pathogens although transmission routes have not been conclusively established. Here we use camera trapping to study wild bird communities on commercial layer and red-legged partridge farms over a one-year timeframe. We also analyze direct and indirect interactions of other bird species with the house sparrow ( ), a potential bridge host. We conducted camera trapping events between January 2018 and October 2019, in two caged layer farms, one free-range layer farm, and two red-legged partridge farms in South-Central Spain. We observed wild bird visits on all types of farms, with the significantly highest occurrence on red-legged partridge farms where food and water are more easily accessible, followed by commercial caged layer farms, and free-range chicken farms. The house sparrow ( ) followed by spotless starlings ( ) was the most encountered species on all farms, with the highest frequency in caged layer farms. On partridge farms, the house sparrow accounted for 58% of the wild bird detections, while on the free-range chicken farm, it made up 11% of the detections. Notably, the breeding season, when food and water are scarce in Mediterranean climates, saw the highest number of wild bird visits to the farms. Our findings confirm that the house sparrow, is in direct and indirect contact with layers and red-legged partridges and other wild birds independent of the type of farm. Contacts between house sparrows and other bird species were most frequent during the breeding season followed by the spring migration period. The species most frequently involved in interactions with the house sparrow belonged to the order Passeriformes. The study provides a comparative description of the composition and seasonal variations of bird communities in different types of layer/ poultry farms in Southern Spain i.e. a Mediterranean climate. It confirms the effectiveness of biosecurity measures that restrict access to feed and water. Additionally, it underscores the importance of synanthropic species, particularly the house sparrow, as potential bridge vector of avian pathogens.