Plastic ingestion presents many potential avenues of risk for wildlife. Understanding which species and environments are most exposed to plastic pollution is a critical first step in investigating the One Health implications of plastic exposure. The objectives of this study were the following: 1) Utilize necropsy as part of ongoing passive disease surveillance to investigate ingested mesoplastics in birds collected in Ontario and Nunavut, and examine the relationships between bird-level factors and ingested debris; 2) evaluate microplastic ingestion compared to ingested mesodebris in raptors; and 3) identify potential sentinel species for plastic pollution monitoring in understudied freshwater and terrestrial (inland) environments. Between 2020 and 2022, 457 free-ranging birds across 52 species were received for postmortem examination. The upper gastrointestinal tracts were examined for mesoplastics and other debris (>2 mm) using standard techniques. Twenty-four individuals (5.3%) retained mesodebris and prevalence varied across species, with foraging technique, food type, and foraging substrate all associated with different metrics of debris ingestion. The odds of ingesting any type of anthropogenic mesodebris was nine times higher for non-raptorial species than for raptors. For a subset of raptors (N = 54) across 14 species, the terminal portion of the distal intestinal tract was digested with potassium hydroxide and microparticles were assessed using stereo-microscopy. Although only one of 54 (1.9%) raptors included in both analyses retained mesodebris in the upper gastrointestinal tract, 24 (44.4%) contained microparticles in the distal intestine. This study demonstrates that a variety of Canadian bird species ingest anthropogenic debris in inland systems, and suggests that life history and behaviour are associated with ingestion risk. For raptors, the mechanisms governing exposure and ingestion of mesoplastics appear to be different than those that govern microplastics. Herring gulls (Larus argentatus) and ring-billed gulls (Larus delawarensis) are proposed as ideal sentinels for plastic pollution monitoring in inland systems.

Avian influenza virus (AIV) is a pathogen with zoonotic and pandemic potential. Migratory birds are natural reservoirs of all known subtypes of AIVs, except for H17N10 and H18N11, and they have been implicated in previous highly pathogenic avian influenza outbreaks worldwide. This study identified and characterized the first isolate of the H13N6 subtype from a Vega gull (Larus vegae mongolicus) in South Korea. The amino acid sequence of hemagglutinin gene showed a low pathogenic AIV subtype and various amino acid substitutions were found in the sequence compared to the reference sequence and known H13 isolates. High sequence homology with other H13N6 isolates was found in HA, NA, PB1, and PA genes, but not for PB2, NP, M, and NS genes. Interestingly, various point amino acid mutations were found on all gene segments, and some are linked to an increased binding to human-type receptors, resistance to antivirals, and virulence. Evolutionary and phylogenetic analyses showed that all gene segments are gull-adapted, with a phylogeographic origin of mostly Eurasian, except for PB2, PA, and M. Findings from this study support the evidence that reassortment of AIVs continuously occurs in nature, and migratory birds are vital in the intercontinental spread of avian influenza viruses.

BACKGROUND: Curbing the potential negative impact of antibiotic resistance, one of our era\'s growing global public health crises, requires regular monitoring of the resistance situations, including the reservoir of resistance genes. Wild birds, a possible bioindicator of antibiotic resistance, have been suggested to play a role in the dissemination of antibiotic-resistant bacteria. Therefore, this study was conducted with the objective of determining the phenotypic and genotypic antibiotic resistance profiles of 100 Escherichia coli isolates of gull and pigeon origin by using the Kirby-Bauer disk diffusion method and PCR. Furthermore, the genetic relationships of the isolates were determined by RAPD-PCR.
RESULTS: Phenotypic antibiotic susceptibility testing revealed that 63% (63/100) and 29% (29/100) of E. coli isolates were resistant to at least one antibiotic and multidrug-resistant (MDR), respectively. With the exception of cephalothin, to which the E. coli isolates were 100% susceptible, tetracycline (52%), kanamycin (38%), streptomycin (37%), ampicillin (28%), chloramphenicol (21%), trimethoprim/sulfamethoxazole (19%), gentamicin (13%), enrofloxacin (12%) and ciprofloxacin (12%) resistances were detected at varying degrees. Among the investigated resistance genes, tet(B) (66%), tet(A) (63%), aphA1 (48%), sul3 (34%), sul2 (26%), strA/strB (24%) and sul1 (16%) were detected. Regarding the genetic diversity of the isolates, the RAPD-PCR-based dendrograms divided both pigeon and gull isolates into five different clusters based on a 70% similarity threshold. Dendrogram analysis revealed 47-100% similarities among pigeon-origin strains and 40-100% similarities among gull-origin E.coli strains.
CONCLUSIONS: This study revealed that gulls and pigeons carry MDR E. coli isolates, which may pose a risk to animal and human health by contaminating the environment with their feces. However, a large-scale epidemiological study investigating the genetic relationship of the strains from a \"one health\" point of view is warranted to determine the possible transmission patterns of antibiotic-resistant bacteria between wild birds, the environment, humans, and other hosts. Video Abstract.

In summer 2022, highly pathogenic influenza A(H5N1) virus reached the herring gull (Larus argentatus subspecies smithsonianus) breeding colony on Kent Island, New Brunswick, Canada. Real-time monitoring revealed a self-limiting outbreak with low mortality. Proactive seabird surveillance is crucial for monitoring such limited outbreaks, protecting seabirds, and tracing zoonotic transmission routes.

Amidst the current biodiversity crisis, the availability of genomic resources for declining species can provide important insights into the factors driving population decline. In the early 1990s, the black-legged kittiwake (Rissa tridactyla), a pelagic gull widely distributed across the arctic, subarctic, and temperate zones, suffered a steep population decline following an abrupt warming of sea surface temperature across its distribution range and is currently listed as Vulnerable by the International Union for the Conservation of Nature. Kittiwakes have long been the focus for field studies of physiology, ecology, and ecotoxicology and are primary indicators of fluctuating ecological conditions in arctic and subarctic marine ecosystems. We present a high-quality chromosome-level reference genome and annotation for the black-legged kittiwake using a combination of Pacific Biosciences HiFi sequencing, Bionano optical maps, Hi-C reads, and RNA-Seq data. The final assembly spans 1.35 Gb across 32 chromosomes, with a scaffold N50 of 88.21 Mb and a BUSCO completeness of 97.4%. This genome assembly substantially improves the quality of a previous draft genome, showing an approximately 5× increase in contiguity and a more complete annotation. Using this new chromosome-level reference genome and three more chromosome-level assemblies of Charadriiformes, we uncover several lineage-specific chromosome fusions and fissions, but find no shared rearrangements, suggesting that interchromosomal rearrangements have been commonplace throughout the diversification of Charadriiformes. This new high-quality genome assembly will enable population genomic, transcriptomic, and phenotype-genotype association studies in a widely studied sentinel species, which may provide important insights into the impacts of global change on marine systems.

In the present study, livers, kidneys and adipose tissue of Yellow-legged Gull (Larus michahellis) were collected. Samples were used to determine relationships between heavy metals/metalloids in liver and kidneys (Hg, Cd, Pb, Se and As) or persistent organic pollutants in adipose tissue (7 PCBs and 11 organochlorine pesticides) with biomarkers of oxidative stress (CAT, GPx, GR, GSH, GST, MDA) analysed in both internal organs. Three possible influencing variables have been studied: age, sex and sampling area. As a result, statistically significant differences (P < 0.05, P < 0.01) were only found according to the sampling area, with differences among the three studied areas found in both organs. Significant positive correlations (P < 0.01) were found in liver (Hg vs. GST; Se vs. MDA) and in kidney (As vs. GR; As vs. GPx; PCB52 vs. CAT; PCB138 vs. CAT). The scarcity in correlations suggests that the levels of pollutants found in animals were not high enough to trigger an effect at the oxidative level.

A recent study demonstrated the possibility that migratory birds are responsible for the global spread of avian rotavirus A (RVA). However, little is known about what types of RVAs are retained in migratory birds. In this study, to obtain information on RVA strains in migratory birds, we characterised an RVA strain, Ho374, that was detected in a faecal sample from a gull species (Larus sp.). Genetic analysis revealed that all 11 genes of this strain were classified as new genotypes (G28-P[39]-I21-R14-C14-M13-A24-N14-T16-E21-H16). This clearly indicates that the genetic diversity of avian RVAs is greater than previously recognised. Our findings highlight the need for investigations of RVA strains retained in migratory birds, including gulls.

Carbapenem resistant Enterobacteriaceae (CRE) are a threat to public health globally, yet the role of the environment in the epidemiology of CRE remains elusive. Given that wild birds can acquire CRE, likely from foraging in anthropogenically impacted areas, and may aid in the maintenance and dissemination of CRE in the environment, a spatiotemporal comparison of isolates from different regions and timepoints may be useful for elucidating epidemiological information. Thus, we characterized the genomic diversity of CRE from fecal samples opportunistically collected from gulls (Larus spp.) inhabiting Alaska (USA), Chile, Spain, Turkey, and Ukraine and from black kites (Milvus migrans) sampled in Pakistan and assessed evidence for spatiotemporal patterns of dissemination. Within and among sampling locations, a high diversity of carbapenemases was found, including Klebsiella pneumoniae carbapenemase (KPC), New Delhi metallo-beta-lactamase (NDM), oxacillinase (OXA), and Verona integron Metallo beta-lactamase (VIM). Although the majority of genomic comparisons among samples did not provide evidence for spatial dissemination, we did find strong evidence for dissemination among Alaska, Spain, and Turkey. We also found strong evidence for temporal dissemination among samples collected in Alaska and Pakistan, though the majority of CRE clones were transitory and were not repeatedly detected among locations where samples were collected longitudinally. Carbapenemase-producing hypervirulent K. pneumoniae was isolated from gulls in Spain and Ukraine and some isolates harbored antimicrobial resistance genes conferring resistance to up to 10 different antibiotic classes, including colistin. Our results are consistent with local acquisition of CRE by wild birds with spatial dissemination influenced by intermediary transmission routes, likely involving humans. Furthermore, our results support the premise that anthropogenically-associated wild birds may be good sentinels for understanding the burden of clinically-relevant antimicrobial resistance in the local human population.

Gulls are ubiquitous in urban areas due to a growing reliance on anthropogenic feeding sites, which has led to changes in their abundance, distribution, and migration ecology, with implications for disease transmission. Gulls offer a valuable model for testing hypotheses regarding the dynamics of influenza A virus (IAV) - for which gulls are a natural reservoir in urban areas. We sampled sympatric populations of Ring-billed (Larus delawarensis), Herring (L. argentatus), and Great Black-backed Gulls (L. marinus) along the densely populated Atlantic rim of North America to understand how IAV transmission is influenced by drivers such as annual cycle, host species, age, habitat type, and their interplay. We found that horizontal transmission, rather than vertical transmission, played an outsized role in the amplification of IAV due to the convergence of gulls from different breeding grounds and age classes. We detected overlapping effects of age and season in our prevalence model, identifying juveniles during autumn as the primary drivers of the seasonal epidemic in gulls. Gulls accumulated immunity over their lifespan, however short-term fluctuations in seroprevalence were observed, suggesting that migration may impose limits on the immune system to maintain circulating antibodies. We found that gulls in coastal urban habitats had higher viral prevalence than gulls captured inland, correlating with higher richness of waterbird species along the coast, a mechanism supported by our movement data. The peak in viral prevalence in newly fledged gulls that are capable of long-distance movement has important implications for the spread of pathogens to novel hosts during the migratory season as well as for human health as gulls increasingly utilize urban habitats.

Antimicrobial resistance genes (ARGs) are environmental pollutants and anthropization indicators. We evaluated human interference in the marine ecosystem through the ocurrence and quantification (real-time PCRs) of 21 plasmid-mediated ARGs in enema samples of 25 wild seabirds, upon admission into rehabilitation: kelp gull (Larus dominicanus, n = 14) and Magellanic penguin (Spheniscus magellanicus, n = 11). Overall, higher resistance values were observed in kelp gulls (non-migratory coastal synanthropic) in comparison with Magellanic penguins (migratory pelagic non-synanthropic). There were significant differences between species (respectively, kelp gull and Magellanic penguin): ARGs occurrence (bla TEM [p = 0.032]; tetM [p = 0.015]; tetA [p = 0.003]; and sulII [p = 0.007]), mean number of ARGs per sample (p = 0.031), ARGs mean load percentage (aadA [p = 0.045], tetA [p = 0.031], tetM [p = 0.016], bla TEM [p = 0.032], sulII [p = 0.008]), percentage of genes conferring resistance to an antimicrobial class (betalactams [p = 0.036] and sulfonamides [p = 0.033]), mean number of genes conferring resistance to one or more antimicrobial classes (p = 0.024]), percentage of multiresistant microbiomes (p = 0.032), and clustering (p = 0.006). These differences are likely due to these species\' contrasting biology and ecology - key factors in the epidemiology of ARGs in seabirds. Additionally, this is the first report of mecA in seabirds in the Americas. Further studies are necessary to clarify the occurrence and diversity of ARGs in seabirds, and their role as potential sources of infection and dispersal within the One Health chain of ARGs.