Search Results (69)

Avian influenza viruses are predominantly associated with waterfowl and shorebirds, and are rarely detected in other avian hosts in nature. In 2021, an H1N1 virus was isolated from a Fieldfare Turdus pilaris in Zaporizhzhia Oblast, Ukraine. A phylogenetic analysis revealed that all eight gene segments belonged to the Eurasian low-pathogenic avian influenza lineages. The highest nucleotide identity of the HA gene was observed with viruses detected in Georgia, Sweden, and Ukraine (99.11%), while the NA gene showed the greatest identity to viruses from Western Europe (99.14–99.57%). Genetic analysis of the HA cleavage site showed a sequence (PSIQSR↓GLF) that contained a single basic amino acid. No deletions were detected in the stalk region of NA gene, and no specific mutations in PB2 protein were found. However, several amino acid substitutions were identified in the HA gene (D204E, S207T, and D239G) that may affect the binding affinity to specific antibodies. The occurrence of this virus in a wild, seemingly healthy thrush indicate that additional surveillance in poorly studied ecological groups such as Passeriformes is warranted. Full article

The review deals with the current knowledge on the global panzootic spread of highly pathogenic avian influenza viruses (HPAIVs), with an emphasis on the H5N1 clade 2.3.4.4b virus. It describes the viral structure, replication, pathotypes and molecular determinants of host range, including sialic-acid receptor usage and key genetic mammalian-adaptation markers (PB2-E627K and PB2-D701N mutations). The host spectrum nowadays extends from wild waterfowl and poultry including seabirds, terrestrial and marine mammals and, based largely on experimental studies or molecular detection, reptiles, amphibians, and fish. Recently, the H5N1 clade 2.3.4.4b virus has shown marked tropism for lactating mammary epithelium in dairy cattle, with virions shed in raw milk. The review reports epidemiology, geographical expansion, clinical presentation, pathogenesis and pathology, diagnosis, immune responses and vaccination approaches across species. It also analyses European Union (EU) and Italian regulatory frameworks, surveillance strategies and biosecurity measures from a One-Health perspective. The review highlights how climate change, wildlife–livestock interfaces, intensive farming and global trade favor viral persistence and genomic reassortment and concludes by stressing strategic actions to limit further host adaptation and panzootic/pandemic risks. Full article

One of the greatest epizootic threats to waterfowl is infection with goose parvovirus (GPV), which is the etiological agent of Derzsy’s disease (DD). Despite the use of prophylactic vaccinations, the disease still occurs in waterfowl. The aim of this study was to conduct a preliminary assessment of the presence of GPV genetic material in transport vehicles based on the results of molecular testing of samples collected from the vehicles between 2017 and 2020. In selected disinfected transport vehicles transporting geese from hatcheries to farms and from farms to slaughterhouses, swabs were collected from transport cages and transport kennel equipment. Samples were collected between 2017 and 2020. Total DNA was then isolated, and PCR amplification was performed to detect the presence of GPV genetic material. The resulting PCR products were sequenced. Based on PCR results, the presence of genetic material from GPV strains originating from disinfected waterfowl transport vehicles was confirmed. From the collected materials, 13 strain sequences were obtained from 2017 to 2020. Based on molecular studies conducted between 2017 and 2020, it should be concluded that despite preventive vaccinations and disinfection of transport vehicles, GPV infection remains a serious epizootic problem in waterfowl flocks in Poland. Full article

Muscovy duck reovirus (MDRV) and novel duck reovirus (NDRV) are major pathogens in duck breeding, leading to substantial economic losses in the waterfowl industry. This study aimed to develop a precise detection and differentiation method for both viruses simultaneously. Specific primers and probes targeting the S3 gene were designed, and a duplex TaqMan-based real-time RT-PCR assay was established following optimization of reaction conditions. The assay demonstrated high amplification efficiency (100.1–106.7%), strong linear correlation (R² > 0.999), and low limits of detection (13–25 copies/µL). Intra- and inter-assay coefficients of variation were below 1.5%, confirming excellent repeatability and stability. Applied to 122 clinical duck tissue samples, the assay detected MDRV in 29.5% (36/122) and NDRV in 39.3% (48/122) of samples, with results fully validated by singleplex RT-PCR assays. Our study provides a reliable, specific, and reproducible tool for surveillance and epidemiological studies of MDRV and NDRV. Full article

Duck enteritis virus (DEV), an epornitic pathogen, causes substantial economic losses in the commercial duck industry and poses persistent risks to wild and migratory waterfowl populations. However, due to the large genomic capacity of the DEV, the understanding of the virulence-associated genes of DEV is still limited. In previous studies, we developed an attenuated strain E74 by serial passage of a virulent strain E1 on primary chicken embryo fibroblasts (CEFs). The bird experiment showed that the mortality rate of E1 on ducks reached 100%, and high-titered viruses were detected in all tested tissue samples. In contrast, the E74 virus has lost its pathogenicity in ducks and can only be detected at a relatively low viral load in the spleen. Furthermore, the E74 stimulated a significant increase in antibodies in the ducks at 7 days post-inoculation. To further investigate the molecular basis of the attenuation of DEV in ducks, the complete genomes of E74 and E1 were sequenced and analyzed. Compared with E1, E74 had a 5152 bp deletion in the UL region, which resulted in the lack of the hypothetical protein, LORF5, UL55 and LORF4 genes. To test the influence of the deletion on the viral pathogenicity, a rescued virus rE1-Δ5152 with the 5152 bp deletion in the UL region was generated on the E1 backbone. Animal experiments showed that the lethality of rE1-Δ5152 in ducks had disappeared. Those findings suggest that the hypothetical protein, LORF5, UL55, and LORF4 genes of DEV are associated with virus virulence, and the flexibility of this region provided excellent insertion sites for exogenous genes when DEV is used as a recombinant vaccine vector. Full article

Reovirus infections pose a significant threat to waterfowl health and productivity globally. This review provides a comprehensive update on various aspects of waterfowl reoviruses (WRVs) affecting domestic duck and goose species. We outline the genetic diversity and evolution of circulating strains. The paper details the array of clinical signs and pathologies observed in infected birds. Most advanced laboratory diagnostic methods, including molecular techniques, are reviewed for their role in rapid and accurate detection, forming the cornerstone of effective surveillance programs. Furthermore, we explore the advancements in WRV vaccine development, covering traditional as well as promising novel approaches. The ongoing challenge of managing WRV infections necessitates integrated surveillance-control programs, prioritizing enhanced diagnostic capabilities and the development of more efficacious and broadly protective vaccines to safeguard populations of domestic ducks and geese. Full article

The Goose/Guandong lineage of highly pathogenic avian influenza virus [A/Goose/Guangdong/1/1996(H5N1)] is the progenitor of the currently circulating Eurasian-lineage highly pathogenic avian influenza H5N1 clade 2.3.4.4b and has been the most consequential highly pathogenic avian influenza lineage globally. Despite increased reports of infections, the extent of exposure and role of wild mammals in the ecology and transmission dynamics of the virus remains poorly understood. We surveyed wild mammals in Ohio, United States to investigate the potential spillover of highly pathogenic H5N1 avian influenza clade 2.3.4.4b. While no active infections—defined as positive results indicative of viral replication and potential propagation—were detected by swab-based molecular tests, serological assays revealed antibodies against multiple avian influenza virus antigens in raccoons and opossums. Specifically, antibodies to avian influenza virus nucleoprotein were detected in 54.9% (n = 61) of samples using enzyme-linked immunosorbent assay; antibodies to Eurasian-lineage highly pathogenic avian influenza H5 clade 2.3.4.4b and North American low pathogenic avian influenza H5 were detected in 43.2% (n = 48) and 22.5% (n = 25) of samples, respectively, using virus neutralization assays; and antibodies to avian influenza virus neuraminidase were detected in 44.1% (n = 49) of samples using enzyme-linked lectin assay. All seropositive animals were sampled at Ohio marshes with previously confirmed highly pathogenic avian influenza H5N1 detections in waterfowl. These findings suggest prior exposure of wild mammals to these viruses without mortality events. Wild mammals may play an intermediary role in the mammalian adaptation of avian influenza A viruses. Therefore, ongoing surveillance of wild mammals is crucial for assessing the risk to public health. Full article

Coronaviruses (CoVs) were first described in poultry in the early 1930s and formally recognized as pathogens of both animal and human populations in the late 1960s. They are now considered among the most abundant viral families in the world. Though their distribution and diversity remain understudied in wild animals, representatives from 13 orders of wild birds worldwide have tested positive for CoVs of the gamma and delta genera over the last 25 years. Many of these wild bird species are in the orders Charadriiformes (shorebirds and their relatives) and Anseriformes (waterfowl including ducks, geese, and swans). Waterfowl are particularly concerning as potential reservoirs for CoVs because they are globally distributed; often congregate in large, mixed-species flocks; and may exist in close proximity to humans and domesticated animals. This review describes the history and current knowledge of CoVs in birds, provides an updated list of global detections of CoVs in 124 species of wild birds as reported in the peer-reviewed literature since 2000, and highlights topics for future research that would help elucidate the role of waterfowl in CoV transmission. Our review reiterates the need for continuous surveillance to detect and monitor CoVs across all bird species and for standardization in data reporting and analysis of both negative and positive results. Such information is critical to understand the potential role of free-ranging birds in the maintenance, evolution, and transmission of the virus. Further, we believe that research on the potential impacts of coronavirus infections and coinfections on avian demographics, especially reproduction in waterfowl, is warranted given known consequences in domestic poultry. Full article

Duck viral enteritis (DVE) is an acute and highly contagious disease that affects waterfowl such as ducks, geese and swans. Duck enteritis virus (DEV) is the pathogen, causing huge economic losses to waterfowl farming in recent years. Establishing a rapid, simple, and visual detection should facilitate the early identification of DEV. After the amplification primers and reaction conditions were optimized, three multienzyme isothermal rapid amplification (MIRA) methods—basic MIRA, MIRA–quantitative PCR (MIRA–qPCR) and MIRA–lateral flow dipstick (MIRA–LFD)—were established to detect DEV. Specificity analyses showed that the three MIRA methods specifically detected DEV, with no cross-reaction with fowl adenovirus serotype 4, novel goose astrovirus, Muscovy duck reovirus, avian influenza virus subtype H9, or duck circovirus. The basic MIRA reaction was completed in 30 min at 35 °C, requiring only a pair of primers. Detection with MIRA–qPCR or MIRA–LFD was completed within 20 min, and the limits of detection were 1 × 10¹ copies/μL for both. MIRA–LFD required no specialized instruments, and the results could be viewed directly with the naked eye. Compared with the traditional PCR, MIRA assays are simple, rapid, and effective and therefore more suitable for the field detection of DEV. Full article

Avian chlamydiosis, primarily caused by Chlamydia psittaci (C. psittaci), poses significant threats to poultry and avian trade. Emerging species such as Chlamydia gallinacea (C. gallinacea), Chlamydia avium (C. avium), and Chlamydia ibidis (C. ibidis) have recently been detected in birds. However, the prevalence and genetic diversity of avian chlamydia in birds within Guangxi remain unknown. In this study, 1744 samples collected from apparently healthy birds were screened, revealing an overall positivity rate of 28.20% (95% CI, 27.58–28.90%, 492/1744) for avian chlamydia. Among poultry, pigeons had the highest positivity rate at 62.30% (95% CI, 55.37–68.69%, 152/244), followed by chickens at 25.05% (95% CI, 21.25–29.23%, 128/511), geese at 18.12% (95% CI, 12.93–24.82%, 29/160), and ducks at 14.14% (95% CI, 11.57–17.26%, 82/580). Additionally, pet and wild birds exhibited positivity rates of 40.35% (95% CI, 34.20–46.83%, 92/228) and 42.86% (95% CI, 24.52–61.83%, 9/21), respectively. Phylogenetic analysis based on the outer-membrane protein A gene indicated that chicken samples belonged to genotypes B of C. psittaci and C. gallinacea. In ducks, genotypes A and B of C. psittaci and C. gallinacea were identified, representing the first documented occurrence of C. psittaci genotypes B and C. gallinacea in ducks in China. The nucleotide sequences from goose samples were initially clustered into genotype A group, while those from pigeons were clustered within genotype B. Furthermore, positive samples from pet birds were classified into genotypes A and B, as well as the C. gallinacea group. Similarly, samples from wild birds were classified into genotypes A and B. These findings suggest that diverse avian chlamydia genotypes are circulating among bird populations in Guangxi, with an expanding host range indicating potential cross-species transmission. Moreover, certain strains derived from waterfowl were found to cluster with those linked to recent psittacosis outbreaks, highlighting the zoonotic potential of avian chlamydia. Therefore, sustained surveillance for avian chlamydia in bird populations and monitoring its genetic evolutionary characteristics are essential to decrease public health risks. Full article

Genetic and antigenic analyses were performed on highly pathogenic avian influenza viruses (HPAIVs) isolated in Hokkaido, northern Japan, during the winter of 2024–2025. Ninety-eight HPAIVs were isolated from feces of waterfowl, tracheal swabs from dead wild birds, or lung homogenates from dead chickens. Phylogenetic analysis of the hemagglutinin (HA) gene from 47 representative isolates revealed that all sequences belonged to the G2d subgroup of clade 2.3.4.4b H5HA, which has been the dominant lineage in Hokkaido since the winter of 2021–2022. These isolates were further divided into three major groups within the subgroup. The HPAIVs isolated in the Republic of Korea, China, and North America were genetically closely related to the Hokkaido isolates, whereas no HPAIVs genetically related to European strains or those detected in North American cattle were identified. Furthermore, HPAIVs isolated from seabirds were genetically closely related to those found in dead marine mammals along the eastern coast of Hokkaido in the spring of 2025. No apparent antigenic differences were observed between the HPAIVs isolated in this study and those from previous seasons. These findings highlight the wide distribution of HPAIVs in Hokkaido, particularly from Asian and North American lineages, and underscore the importance of continuous surveillance. Full article

Wild birds, particularly migratory waterfowl (family Anatidae), are the primary reservoir of avian influenza viruses, playing a key role in their transboundary spread. In the winter of 2016/2017, the H5N8 strain was first recorded in Serbia, with 20 outbreaks confirmed in wild birds by 2021, mostly involving mute swans in the Vojvodina region. From 2021 onward, the dominant strain was H5N1, with 38 confirmed outbreaks up to 2023, primarily affecting mute swans, black-headed gulls, and common cranes. Sporadic H5N2 outbreaks were also detected, with two cases in 2021 and 2023. Due to its rich ornithofauna, natural reserves, and habitats suitable for migratory birds, the Vojvodina region has been officially designated as a high-risk zone by the Veterinary Directorate of the Ministry of Agriculture, Forestry and Water Management of the Republic of Serbia. While sporadic cases occurred in backyard poultry, commercial farms remained unaffected. Infections peaked in autumn and early spring. Control measures included enhanced biosecurity, movement restrictions, and removal of dead birds to protect domestic poultry. Despite the circulation of avian influenza virus in wild birds, Serbia’s commercial poultry industry avoided outbreaks and major economic losses. Including outbreak data provided insight into the scale and persistence of avian influenza threats in this region. Full article

The rapid expansion of the meat duck industry in China has intensified environmental challenges, particularly those related to managing high-moisture duck manure. Fermentation bed systems, utilizing rice husks as a primary substrate, offer a sustainable solution by promoting waste decomposition and improving animal welfare. This study investigated microbial diversity in rice husk-based fermentation bed materials across different usage durations to assess their ecological feasibility. Samples were collected from a duck farm in Linyi, China, after one, three, five and seven batches of duck rearing (21 days per batch). Microbial communities were analyzed using polymerase chain reaction–denaturing gradient gel electrophoresis (PCR-DGGE), followed by cluster analysis, principal component analysis (PCA) and sequencing of recovered DGGE bands. The results revealed significant shifts in microbial composition, with low similarity (18% overall) and distinct abundance patterns among groups. Bacteroidetes abundance increased with prolonged usage, while Staphylococcus aureus was only detected in the first batch. A total of 32 sequenced bands identified dominant phyla, including Actinobacteria, Proteobacteria, Firmicutes and Bacteroidetes. Group 4 (seven batches) exhibited the highest microbial diversity and richness (Shannon index: 2.68; mean abundance: 16.33 bands), which was attributed to organic matter accumulation and nutrient release during fermentation. These findings demonstrate that rice husk-based fermentation beds maintain robust microbial diversity over time, effectively supporting waste degradation and duck health. We conclude that rice husks are a viable, eco-friendly substrate for waterfowl fermentation bed systems, with periodic microbial supplementation recommended to enhance long-term efficacy. This work provides critical insights for optimizing sustainable livestock farming practices. Full article

Novel waterfowl reoviruses (nWRVs) have been reported in several countries, but their circulation and genetic characteristics in Vietnam remain poorly understood. In this study, we investigated nWRVs in northern Vietnam through molecular detection, virus isolation, experimental infection in ducklings, and molecular analysis of the sigma C-encoding (sC) gene. We also applied immunoinformatic tools to explore the antigenic and structural features of the sC protein. nWRVs were detected in 15.6% of tested samples across ten provinces. Three isolates were successfully recovered, all showing a characteristic cytopathic effect—syncytium formation—in Vero cells. When tested in ducklings (n = 72), the isolates caused disease of varying severity, but all induced characteristic gross and microscopic lesions, particularly ecchymotic hemorrhages and large necrotic foci in the liver and spleen. Phylogenetic analysis based on sC sequences placed the Vietnamese isolates (n = 14) within the nWRV clade, with evidence of two genetically distinct groups. Our immunoinformatic analysis identified four predicted B-cell epitopes located in the head and body domains of the sC protein, with little variation. Full article

Anseriformes (waterfowl) and Charadriiformes (shorebirds) are well-recognized natural reservoirs of low pathogenic (LP) influenza A viruses (IAVs). Historically, LP IAVs circulate among healthy individuals during seasonal, and often transcontinental, migrations. However, following the introduction of clade 2.3.4.4b highly pathogenic (HP) A/Goose/Guangdong/1/1996 lineage H5 IAV to North America in 2021, countless wild birds succumbed to fatal infections across the Western Hemisphere. Due to their small size and cryptic plumage patterns, opportunities for carcass recovery and postmortem evaluation in sanderlings (Calidris alba) and other shorebirds are rare. A multispecies mortality event in coastal Virginia, USA, in March–April 2024 included sanderlings among other wild bird species. Nine sanderlings underwent postmortem evaluation and clade 2.3.4.4b H5 IAV RNA was detected in pooled oropharyngeal-cloacal swabs from 11/11 individuals by real-time reverse transcription polymerase chain reaction. Histopathology was similar to that in waterfowl and included necrosis in the pancreas and brain and less commonly in the gonad, adrenal gland, spleen, liver, and intestine. Immunohistochemistry revealed IAV antigen labeling in necrotic neurons of the brain (neurotropism) and epithelial cells of the pancreas, gonad, and adrenal gland (epitheliotropism). Describing HP IAV-attributed pathology in shorebirds is key to understanding ecoepidemiology and population health threats in order to further document and compare pathogenesis among avian species. Full article