Search Results (121)

H5 subtype avian influenza virus (AIV) can infect both chickens and ducks, leading to substantial economic losses. Nevertheless, certain strains cause silent infections in ducks. In this study, a goose-origin clade 2.3.4.4h H5N6 AIV was isolated, which caused high mortality in mixed-gender white leghorn chickens but no deaths in mixed-gender mallard ducks. After independent serial in vitro passage in duck embryo fibroblasts (DEFs) and in vivo passage in specific-pathogen-free (SPF) ducks, the DEF-passage 10 (P10) virus induced markedly higher mortality rates and viral loads in SPF ducks compared to the DEF-P1 virus and the original parental virus prior to passage. Similarly, the in vivo-passaged P3 and P4 viruses exhibited significantly higher mortality rates than the P1 virus in SPF ducks, with 100% mortality and markedly increased viral titers in the organs. A whole-genome SNP analysis identified seven high-frequency mutations in the M1, NA and NS1 proteins. The NS1-F161L substitution virus exhibited significantly increased mortality rates, viral loads in multiple tissues, and a robustly induced innate immune response in ducks. Furthermore, dynamic evolutionary variations in the NS1 protein among global H5 avian influenza viruses revealed that the NS1-F161L substitution became dominant in clade 2.3.4.4b viruses in 2021 and subsequent years. Collectively, our findings demonstrate that host-driven adaptation can rapidly increase the pathogenicity of H5N6 AIVs in ducks and identify NS1-F161L as a critical virulence marker. These results offer novel insights relevant to the molecular surveillance, virulence prediction, and risk assessment of circulating H5 AIVs in waterfowl. Full article

The highly pathogenic avian influenza virus HPAI A(H5N1) genotype AF was detected in southern Europe during the 2021/2022 season and spread widely. It emerged in Bulgaria in 2022/2023, mainly affecting mallard ducks. The DA genotype of the virus was detected in a diverse group of birds, including wild birds, zoo birds, and domestic poultry, across a wide area of eastern and southern Europe in 2023. In Bulgaria, following its introduction in 2023, the DA genotype became the predominant virus in laying hens. During 2024–2025, DA spread throughout the country, displacing AF from mallard flocks. The predominant subtype in Europe in 2025 was H5N1 genotype DI.2. This genotype became dominant after December 2024, accounting for over 90% of viruses within the EA-2024-DI genotype lineage, and has been detected in a wide range of bird species. In Bulgaria, DI.2 was identified in only one outbreak in a flock of laying hens in autumn 2024 and in a single case involving a western marsh harrier (Circus aeruginosus) in early 2025. These observations are consistent with a pattern of putative hidden circulation of avian influenza virus in duck farms in Bulgaria, potentially establishing a cycle of continuous circulation of the same viral subtype. In this study, we analysed viruses originating from Bulgaria, with a particular focus on EA-2024-DI genotype DI.2, and examined mutations related to host cell receptor binding, host specificity shifts, ligand binding, antibody recognition sites, viral oligomerization interfaces, and other functional regions. Some of these mutations have been associated with antigenic drift, immune escape, and virulence. Importantly, several are linked to changes in host specificity, a critical step in the potential transition of avian influenza viruses to humans. Consequently, such mutations represent key factors in the spread of highly pathogenic avian influenza and may pose a pandemic risk. Full article

Today, machine learning (ML) is generally considered a potent and efficient tool for addressing studies in various diverse domains, including image processing and event prediction on a timescale. ML represents complex relations between features, and these mappings between such features may be applied in simulations of time-dependent events, such as the behavior of animals. Still, ML inherently strongly depends on extensive and consistent datasets, a fact that reveals both the benefits and drawbacks of ML. In the use of ML, insufficient or skewed data can limit the ability of algorithms to accurately predict or generalize possible states. To overcome this limitation, this work proposes an integrated hybrid approach that combines machine learning with methods from cognitive science, here especially inspired by the ACT-R model to approach cases of missing or unbalanced data. By incorporating cognitive processes such as memory, perception, and attention, the model accounts for the internal mechanisms of decision-making and environmental interaction where traditional ML methods fall short. This approach is particularly useful in representing states that are not directly observable or are underrepresented in the data, such as rare behavioral responses for animals, or adaptive strategies. Experimental results show that the combination of machine learning for data-driven analysis and cognitive ‘rule-based’ frameworks for filling in gaps provides a more comprehensive model of animal behavior. The findings suggest that this hybrid approach to simulation models can offer a more robust and consistent way to study complex, real-world phenomena, especially when data is inherently incomplete or unbalanced. Full article

Rapid global urbanization has led to the loss and degradation of many natural habitats, causing numerous bird species to inhabit and breed in cities. Here we investigated the influence of multiple factors on the number of chicks of the four common waterbird species, from Anatidae [Mallard (Anas platyrhynchos), Mute Swan (Cygnus olor)] and from Rallidae [Eurasian Coot (Fulica atra), Common Moorhen (Gallinula chloropus)], nesting in Gdańsk (Poland) in 2020 and 2021. We found that the harsh winter before the 2021 season may have resulted in a lower number of chicks in rallids. Rainfall and higher temperatures during breeding season increased the number of rallids’ chicks. Larger waterbodies were associated with a lower number of chicks (except for Moorhen). However, a longer shoreline was related to a higher number of chicks of all species. The Normalized Difference Moisture Index, indicating absence of urban fabric, positively impacted the number of chicks of all species, except for Mallard. The distance of waterbody from areas with varying degrees of urbanization had a diverse effect on the number of chicks of each species, except for Swan. Our results emphasize the importance of urban reservoirs for breeding birds and highlight the need to preserve natural features, such as allowing bank vegetation and reeds to grow, to provide nesting sites and shelter. Full article

The Port of Gdynia is the largest Baltic Sea port handling agricultural products and has adopted green port policies focused on sustainable development. Despite these measures, minor, unavoidable losses occur at transhipment points. With monthly grain transhipments ranging from 62,000 to 96,000 tonnes, accidental losses provide a significant supplementary food source for birds. Four species benefit most: the mallard, herring gull, common gull, and black-headed gull. These birds congregate primarily at transhipment sites, forming one of the largest winter concentrations in Poland. Together, they account for 93–96% of all waterbirds present in the port during winter, with maximum counts of 6232 mallards, 5815 herring gulls, 4482 common gulls, and 1624 black-headed gulls. The abundance of the first three species even exceeds the average winter counts of the nearby Natura 2000 site “Puck Bay,” established for its significance for wintering waterbirds. The energy content of spilled grain is sufficient to meet the daily energy requirements of these species, supporting their high numbers. These findings suggest that, despite intensive shipping and human activity along the port’s quays, unintentional food availability at port transhipment sites can support high waterbird abundances during winter, highlighting the potential conservation value of managing incidental food resources in industrial port environments. Full article

Species of the orders Charadriiformes and Anseriformes serve as the primary long-distance disseminators of various avulaviruses. The most economically significant among them is Newcastle disease virus (NDV), or Avian orthoavulavirus 1 (AOAV-1), which causes diseases of varying severity in both domestic and wild birds. Other avulaviruses have been studied to a much lesser extent, and for most of them, only single isolates are known, which does not allow a comprehensive assessment of their potential threat. To evaluate the biological diversity and potential risks posed by avian paramyxoviruses spread by wild waterfowl during autumn migration, fecal samples from mallards (Anas platyrhynchos) (n = 3604) were collected at water bodies in Moscow and the Moscow Region between 2008 and 2024. From these samples, AOAV-1 (n = 4) and Avian paraavulavirus 4 (APMV-4) (n = 9) were isolated and partially sequenced. Phylogenetic analysis revealed that all AOAV-1 isolates belong to genotype 1 of class II, while all APMV-4 isolates belong to the Eurasian subgenotype of genotype 1. Analysis of the F protein cleavage site motif indicated conformity with the consensus sequences characteristic of lentogenic and non-pathogenic avian paramyxoviruses in all isolates. Full article

Avian influenza viruses (AIVs) of H10 subtype are able to circulate in domestic and wild bird populations but can also spill over and adapt to mammals, posing a continuous risk to biodiversity conservation, veterinary health, and public health. In the present study, we assessed the zoonotic potential of nine H10 AIVs isolated from waterbirds during surveillance and research studies carried out in Italy between 1994 and 2007. Overall, six H10NX strains from wild mallards (n. 1 H10N2, n. 5 H10N7), one H10N7 strain from domestic mallards, and two H10N8 strains from Eurasian coots were sequenced by next-generation sequencing (NGS). HA phylogenetic analysis indicated a marked divergence between viruses from these two sympatric waterbird species and showed a close relationship between three H10N7 strains from wild mallard and one H10N7 isolate of domestic origin. Sequence analysis revealed the presence of several molecular markers, associated with increased zoonotic potential, including the PB2-A588V mutation found in the Eurasian coot H10N8 viruses and previously linked to mammalian adaptation in H10 strains. Molecular analysis also showed that all H10 viruses were susceptible to the major approved classes of influenza antivirals (inhibitors of neuraminidase, matrix-2, and polymerase acid protein). Moreover, phenotypic assay confirmed their susceptibility to oseltamivir and zanamivir drugs. From an ecological perspective, we found that different H10 gene pools seem to be harboured in different waterbird species sharing the same environment; additionally, a bidirectional transmission of H10 mallard isolates occurred between natural and anthropic ecosystems. Overall, our findings account for the need of continuous monitoring of AIVs belonging to the H10 subtype. Full article

Wetlands play a vital role in conserving waterbirds, particularly along major European river systems such as the Danube River and its tributaries. To promote the importance of wetlands and address the lack of data on bird biodiversity in aquatic ecosystems, this study was conducted to assess the baseline status of a demonstration site within the European project DaWetRest. The research focused on a lesser-studied pilot area, the Danube North of Kopački rit, near the village of Draž, located in the tri-border region of Croatia, Hungary, and Serbia. Systematic ornithological monitoring was carried out monthly from January to December 2024 across three monitoring areas (total transect length: 4200 m). A total of 26 bird taxa were recorded, comprising 2148 individual observations. The most dominant species were the Mallard (Anas platyrhynchos), Grey Heron (Ardea cinerea), and Great Cormorant (Phalacrocorax carbo). Conversely, the species that were the least present were White Stork (Ciconia ciconia), Squacco Heron (Ardeola ralloides), Great Crested Grebe (Podiceps cristatus), Eurasian Teal (Anas crecca), and Black Stork (Ciconia nigra). This study also examines the seasonal dynamics of waterbirds, providing essential baseline data for evaluating the effectiveness of upcoming restoration measures planned for the area. Full article

Changes in the habitat of wild mallard ducks (Anas platyrhynchos L.) and thus in their diet can result in significant differences in the content of sodium and potassium in their tissues and organs. There is little data in the available literature regarding the qualitative analysis of mallard meat and organs. The aim of the study was to determine the sodium and potassium content in biological material (breast muscle, leg muscles, and liver) from wild mallards and the effect of sex and place of origin (hunting district) on these parameters. Sodium and potassium in the biological material were analyzed by inductively coupled plasma atomic emission spectroscopy (ICP-OES). The sodium and potassium levels in the tissues were shown to be influenced by the sex of the mallards and the site where they were harvested. Sodium content was significantly higher in the liver of male mallards than in females. In most cases, the tissues and organs of mallards harvested in the Siedlce hunting district had higher levels of sodium and potassium, apart from potassium content in the breast muscle. This may indicate greater abundance of these elements in this district. Full article

Ducks exhibit substantial ecological and dietary diversity, which drives morphological and functional adaptations in their digestive systems. This study analyzed the small intestine and cecum of three wild duck species: Mallard (Anas platyrhynchos), Tufted Duck (Aythya fuligula), and Green-Winged Teal (Anas crecca) collected post-mortem. Histomorphometric analysis and immunohistochemistry (IHC) with the pan-neuronal marker HuC/D were performed. The Tufted Duck showed the thickest intestinal muscle layers, particularly in the duodenum and ileum, and the largest enteric ganglia, indicating adaptation to a fibrous and protein-rich diet. The Mallard displayed the longest villi and deepest crypts, consistent with its omnivorous diet rich in plant material. The Green-Winged Teal, which consumes highly digestible insect-rich food, had the shortest villi and thinnest muscle layers. Differences in enteric ganglion size and organization among species suggest varying neuroregulatory demands in different gut segments. These findings confirm that intestinal morphology and enteric nervous system (ENS) structure are tightly linked to dietary specialization and ecological strategies. The results highlight the high adaptive plasticity of the avian digestive system in response to feeding behavior. Full article

Vitamin D (VD) plays a critical role in human health, with deficiencies linked to a range of adverse outcomes, including compromised immune function and increased disease risk. While environmental factors such as sunlight exposure and diet influence circulating VD levels, genetic variation is a significant and underappreciated contributor to interindividual differences in serum 25-hydroxyvitamin D [25(OH)D] concentrations. This review provides a comprehensive summary of genetic variants in key genes involved in VD synthesis (e.g., DHCR7, cyp2r1, cyp27b1), transport (GC), and metabolism (cyp24a1, cyp3a4), as well as in cholesterol transport proteins (SCARB1, CD36, NPC1L1). We examine how single-nucleotide polymorphisms (SNPs) and rare mutations in these genes affect enzyme activity, VD bioavailability, and overall 25(OH)D status. Importantly, we highlight evidence supporting gene-by-environment interactions and population-specific allele frequencies that further shape individual VD responses. In the context of clinical nutrition and precision health, these findings support the development of genomic risk scores (GRSs) to identify individuals at risk for deficiency or toxicity and guide personalized VD supplementation strategies. Regular monitoring of serum 25(OH)D alongside genetic screening may improve clinical outcomes by helping to achieve optimal VD immunosufficiency while minimizing the risk of adverse effects. Full article

Gopher tortoises (Gopherus polyphemus) are threatened burrowing keystone ecosystem engineers indigenous to open uplands in the Southeastern United States. Perils to the species include habitat degradation and fragmentation, anthropogenic disturbances, predation, parasites, and disease. Problems are severe in the SE Florida study area due to coastal urban sprawl, confining the tortoises in small, scattered, unnatural pockets subject to novel stresses. The annual South Florida February to ca. late May dry season became a severe drought in 2025. The present project centered on the broad question of foodplant resilience through the drought. The tortoise-grazed areas host three dominant groundcover species, in order of abundance: non-native Richardia grandiflora, native grass Paspalum setaceum, and non-native sedge Fimbristylis cymosa. Key findings were as follows: 1. The most abundant and most-often grazed species, Richardia grandiflora, when tortoises were excluded, expanded despite the drought (from 39% to 49.5% mean coverage). Under combined drought and grazing, that species cover decreased slightly (42.5% to 39.4%). Tortoise-free, Paspalum setaceum declined slightly during the drought (32.7% to 27.1% mean coverage), and showed mixed results with little net effect exposed to drought and to grazing. Never observed to be grazed during the study, Fimbristylis cymosa formed a nearly monospecific lawn in a sizeable portion of the study area. During the drought, it mostly browned, retaining green rosette centers, and tortoise exclusion showed no discernable effect. With transition to late spring, however, with increased rainfall, tortoise exclusion allowed rapid competition from grasses among the Fimbristylis rosettes. Adjacent unenclosed grazing, by contrast, maintained the Fimbristylis lawn without increase in grass coverage. Conclusions are that the two chief “fodder” species, Richardia grandiflora and Paspalum setaceum, were robust to drought and grazing. The introduced Fimbristylis cymosa appears to be facilitated by selective grazing-suppressing grass competitors. Full article

Nocardia spp. are opportunistic pathogens of humans, domestic animals, and wildlife that can cause high levels of morbidity and mortality. Here, we present a unique case of nocardial airsacculitis in a free-ranging mallard (Anas platyrhynchos) from Arizona, USA, and compare it to the hosts, geographic distribution, diagnostic methodology, and infection site of known nocardiosis cases in birds. A gross necropsy, histopathology, and bacterial culture were performed. There were no gross findings associated with the nocardiosis. Histopathology showed multiple granulomas expanding the air sac with intralesional filamentous bacteria that were Grocott’s methenamine silver-positive, Fite–Faraco and Ziehl–Neelsen acid-fast, positive with the Periodic acid–Schiff reaction, and variably Gram-positive. The organism was isolated in culture and identified as Nocardia cyriacigeorgica based on the sequencing of a 463 bp portion of the 16S rRNA gene. While reports of nocardiosis in the class Aves are rare and some are possibly misdiagnosed due to limited diagnostics, cases are reported globally, sometimes resulting in epizootics. More information is needed to understand whether immunosuppression plays a role in disease development in birds. Known to be an emerging pathogen in humans, N. cyriacigeorgica can be considered as a differential diagnosis for pulmonary and potentially cutaneous or disseminated infections in birds. Full article

Background/Objectives: Outbreaks of highly pathogenic avian influenza virus (AIV) result in significant financial losses and the death or depopulation of millions of domestic birds. Early and rapid detection and surveillance are needed to slow the spread of AIV and prevent its spillover to humans. The volatile metabolome (i.e., the pattern of volatile metabolites emitted by a living subject) represents one such source of health information that can be monitored for disease diagnosis. Indeed, dogs have been successfully trained to recognize patterns of “body odors” associated with many diseases. Because little is known regarding the mechanisms involved in the alteration of the volatile metabolome in response to health perturbation, questions still arise regarding the specificity, or lack thereof, of these alterations. Methods: To address this concern, we experimentally infected twenty mallard ducks with one of two different strains of low-pathogenic AIV (ten ducks per strain) and collected cloacal swabs at various time points before and after infection. Results: Headspace analyses revealed that four volatiles were significantly altered following infection, with distinct profiles associated with each viral strain. The volatiles that differed between strains among post-infection sampling periods included ethylbenzyl ether (p = 0.00006), 2-phenoxyethanol (p = 0.00017), 2-hydroxybenzaldehyde (p = 0.00022), and 6-methyl-5-hepten-2-one (p = 0.00034). Conclusions: These findings underscore that AIV-induced changes to the volatile metabolome are strain-specific, emphasizing the need for disease-specific profiling in diagnostic development. Full article

The study of neuronal electrical activity and spatial organization is essential for uncovering the mechanisms that regulate neuronal electrophysiology and function. Mathematical models have been utilized to analyze the structural properties of neuronal networks, predict connectivity patterns, and examine how morphological changes impact neural network function. In this study, we aimed to explore the role of the actin cytoskeleton in neuronal signaling via primary cilia and to elucidate the role of the actin network in conjunction with neuronal electrical activity in shaping spatial neuronal formation and organization, as demonstrated by relevant mathematical models. Our proposed model is based on the polygamma function, a mathematical application of ramification, and a geometrical definition of the actin cytoskeleton via complex numbers, ring polynomials, homogeneous polynomials, characteristic polynomials, gradients, the Dirac delta function, the vector Laplacian, the Goldman equation, and the Lie bracket of vector fields. We were able to reflect the effects of neuronal electrical activity, as modeled by the Van der Pol equation in combination with the actin cytoskeleton, on neuronal morphology in a 2D model. In the next step, we converted the 2D model into a 3D model of neuronal electrical activity, known as a core-shell model, in which our generated membrane potential is compatible with the neuronal membrane potential (in millivolts, mV). The generated neurons can grow and develop like an organoid brain based on the developed mathematical equations. Furthermore, we mathematically introduced the signal transduction of primary cilia in neurons. Additionally, we proposed a geometrical model of the neuronal branching pattern, which we described as ramification, that could serve as an alternative mathematical explanation for the branching pattern emanating from the neuronal soma. In conclusion, we highlighted the relationship between the actin cytoskeleton and the signaling processes of primary cilia. We also developed a 3D model that integrates the geometric organization unique to neurons, which contains soma and branches, such that the mathematical model represents the interaction between the actin cytoskeleton and neuronal electrical activity in generating action potentials. Next, we could generalize the model into a cluster of neurons, similar to an organoid brain model. This mathematical framework offers promising applications in artificial intelligence and advancements in neural networks. Full article