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  Abstract In the present study, we assessed the pathogenicity of H5N8 avian influenza viruses belongs to the clade 2.3.4.4b in chicken. Birds of three different dose groups, 10 2 , 10 4 , and 10 6 EID 50 were used in the study. No mortality was observed in 10 2 EID0 group. Percent cumulative mortality of 10 4 and 10 6 EID 50 group was 66.67 and 100 %, respectively. Varying duration of MDT of 3.2 and 2 days was observed in 10 4 and 10 6 EID 50 group, respectively. The CID 50 of virus was found to be 10 4.5 EID 50 . High no. of viral RNA copies were found both in oropharyngeal and cloacal swabs and in various organs of birds infected in 10 4 and 10 6 EID 50 group. Significant gross and histological changes and presence of viral antigen in various organs were observed in 10 4 and 10 6 EID 50 group. So, the study concludes that Indian HPAI, H5N8 isolates are highly pathogenic in nature to chicken by affecting most organs systemically. CID 50 of this H5N8 virus indicates poor adaption ...

  Abstract Highly pathogenic avian influenza (HPAI) H5N8 virus, first identified in late 2016 in Egypt, continues to circulate and has replaced the previously dominant HPAI H5N1 virus of clade 2.2.1. In this study, HPAI H5N8 was detected on 23 commercial poultry farms in Egypt . Complete genome sequences of three isolates collected in 2021 were obtained using next-generation sequencing (NGS) and subjected to genetic characterization. Phylogenetic analysis showed these isolates to belong to clade 2.3.4.4b, comprising two genotypes: EA-2021-Q and EA-2020-A . Molecular analysis of the haemagglutinin (HA) protein revealed the presence of T156A and V538A substitutions in the duck isolate and an N183S substitution in the chicken isolate . Several additional nonsynonymous mutations were identified, including 147I and 504V in the PB2 protein , 127V, 672L, and 550L in the PA protein , 64F and 69P in the M2 protein , and 42S in the NS1 protein . Comparative analysis of HA antigenic sites bet...

  Abstract Finland faced an outbreak of highly pathogenic clade 2.3.4.4b A(H5N1) avian influenza in 2023, which spread from wild birds to fur farms . Vaccinations of at-risk individuals began in June 2024 using the MF59-adjuvanted inactivated A(H5N8) vaccine (Seqirus; A/Astrakhan/3212/2020, clade 2.3.4.4b). Here, in an observational study , we assessed vaccine-induced immune responses in occupational at-risk individuals participating in the phase IV trial , including virus-specific antibody (n = 39 individuals) and T-cell (n = 18 individuals) responses. Vaccination elicited functional antibodies against the vaccine virus and two heterologous clade 2.3.4.4b strains associated with outbreaks on Finnish fur farms and dairy cattle in the United States . Among previously unvaccinated individuals, seroprotection rates against the vaccine virus were 83% (95% CI 70–97%) by microneutralization assay (titre ≥20) and 97% (90–100%) by haemagglutination inhibition assay (titre ≥40). In those pr...

  Highlights --  We conducted surveillance for influenza A viruses at live bird markets in northern Vietnam. --  Six different subtypes of influenza A virus were found co-circulating in the markets. --  Notable genetic mutations were found across many genes. --  These markets have great potential to generate new pandemic influenza A virus strains. Abstract Objectives Live bird markets (LBMs) in Asia have often been the source of human infections with avian influenza virus (AIV). Methods From July 2021 to August 2023, we employed a One Health approach in conducting periodic surveillance for novel influenza A viruses in five LBMs in northern Vietnam. Specimens were studied with egg culture, molecular assays, Sanger sequencing, and next-generation sequencing. Results We studied a total of 688 human, avian, and bioaerosol specimens . Among these, 118 ( 17.2% ) were found to have molecular evidence of AIVs . Next-generation sequencing of 92 isolates revealed multiple...

  ABSTRACT For over two decades, avian influenza virus (AIV) has significantly impacted the Egyptian poultry population , with multiple subtypes and genotypes contributing to significant economic and agricultural losses. As part of an ongoing national surveillance effort , this study aimed to monitor and genetically characterize AIV circulation across various poultry sectors in Egypt . Between 2022 and 2024, a total of 446,790 swab samples were collected, representing commercial farms (n = 25,057), backyard flocks (n = 403), and live bird markets “LBM” (n = 1250) to assess the prevalence and genetic diversity of circulating AIV strains. A total of 173 sampling units were found positive for high pathogenicity (HP) AIV H5 , including farms (n = 17), backyards (n = 11), and LBMs (n = 145). The HPAIV of H5N8 subtype was dominant (n = 75) over the H5N1 (n = 27) subtypes among all sectors and bird species ( chickens, ducks, turkeys ). Whole genome sequence analysis of positive H5 samples...

Abstract Viral pandemics such as COVID-19 have demonstrated long-term neurological consequences , including memory impairment and depression , emphasizing the importance of understanding virus-brain interactions [1]. Similar concerns have been raised for Influenza A virus (IAV), which has been implicated in neurodegenerative disorders [2, 3]. In this study, we investigated the neuropathological effects of highly pathogenic avian influenza (HPAI) H5N1 and H5N8 strains in a mouse model . Although viral RNA was detected in the brain post-infection, no viral proteins were found, suggesting limited or transient brain replication . Despite this, infected brains showed significant neuronal damage , including axonal loss and nuclear condensation , as evidenced by immunofluorescence and Nissl staining. We also observed pathological changes in TDP-43, including conformational alterations and increased phosphorylation, which required antigen retrieval for detection, features reminiscent of those ...

Abstract Avian influenza virus (AIV) is a significant global concern, causing widespread mortality in wild birds, domestic poultry and most recently wild and domestic mammals . This study presents a retrospective analysis of AIV detections in the Republic of Ireland . Data was sourced from official surveillance databases, peer-reviewed literature and grey literature sources. Spatio-temporal, host-specific and subtype patterns were assessed using descriptive statistics, chi-square tests, linear regression and kernel density estimations. A total of 2,888 confirmed AIV detections were recorded from 25 of Ireland's 26 counties . Wild birds accounted for 98.7% of detections, with domestic birds comprising 1.3% and two detections in foxes . H5N1 was the most prevalent subtype (96.7%) followed by H5N8 and H6N1 . Spatial clustering was observed in urban areas, particularly Dublin . The highest seasonal peak occurred during summer, contrasting with traditional winter-associated patterns. Se...

Abstract H5Nx clade 2.3.4.4b high-pathogenicity avian influenza viruses (HPAIVs) have decimated wild bird and poultry populations globally since the autumn of 2020. In the United Kingdom (UK) and in continental Europe , the H5N8 subtype predominated during the first epizootic wave of 2020/21 , with few detections of H5N1. However, during the second (2021/22) and third (2022/23) epizootic waves, H5N1 was the dominant subtype. The rapid shift in dominance from H5N8 to H5N1 was likely driven by a combination of virological, immunological, and/or host-related factors. In this study, we compared viral fitness and immunological responses in ducks , a key reservoir species, using dominant genotypes of H5N1 (genotype AB) and H5N8 (genotype A) from the second wave. While viral shedding dynamics were similar for both viruses, H5N8 was more pathogenic . Antigenic analysis of post-infection duck sera revealed that the haemagglutinin (HA) protein was antigenically similar across clade 2.3.4.4b H5 H...

Abstract Highly pathogenic avian influenza (HPAI) represents a threat to animal and human health , with the ongoing H5N1 outbreak within the H5 2.3.4.4b clade being the largest on record. However, it remains unclear what factors have contributed to its intercontinental spread . We use Bayesian additive regression trees, a machine learning method designed for probabilistic modelling of complex nonlinear phenomena, to construct species distribution models (SDMs) for HPAI clade 2.3.4.4b presence. We identify factors driving geospatial patterns of infection and project risk distributions across Europe . Our models are time-stratified to capture both seasonal changes in risk and shifts in epidemiology associated with the succession of H5N6/H5N8 by H5N1 within the clade . While previous studies aimed to model HPAI presence from physical geography, we explicitly consider wild bird ecology by including estimates of bird species richness, abundance of specific taxa, and "abundance indices...

Abstract H5Nx clade 2.3.4.4b high-pathogenicity avian influenza viruses (HPAIVs) have decimated wild bird and poultry populations globally since the autumn of 2020. In the United Kingdom (UK) and in continental Europe , the H5N8 subtype predominated during the first epizootic wave of 2020/21, with few detections of H5N1 . However, during the second (2021/22) and third (2022/23) epizootic waves , H5N1 was the dominant subtype. The rapid shift in dominance from H5N8 to H5N1 was likely driven by a combination of virological, immunological, and/or host-related factors . In this study, we compared viral fitness and immunological responses in ducks , a key reservoir species, using dominant genotypes of H5N1 (genotype AB) and H5N8 (genotype A) from the second wave. While viral shedding dynamics were similar for both viruses, H5N8 was more pathogenic . Antigenic analysis of post-infection duck sera revealed that the haemagglutinin (HA) protein was antigenically similar across clade 2.3.4.4b H5...

Abstract The introduction and subsequent detection of highly pathogenic avian influenza (HPAI) in poultry is influenced by the virus replication fitness, transmission fitness, and virulence in poultry. These viral fitness parameters are important for implementing surveillance and control measures for poultry. This study investigates the potential application of an avian in vitro model using primary chicken embryo (CEF) and duck embryo fibroblasts (DEF) to identify the viral fitness for a reference panel of eight dominant HPAI clade 2.3.4.4 virus genotypes : four H5N1 viruses isolated between 2021 and 2024, as well as three H5N8 and one H5N6 virus isolated between 2014 and 2020. Infectious virus titre and cytopathogenicity were measured in the primary cell cultures over time and these data were analysed using a mathematical model which delineates cell populations into susceptible, latent, infectious, and dead compartments. In addition to obtaining traditional virological parameters such...

 A wild Booted Eagle in HaZafon Region. Source: WOAH,  https://wahis.woah.org/#/in-review/6408 ____

Abstract The H9N2 subtype of avian influenza virus poses significant challenges to global poultry and human health . During the active surveillance of avian influenza virus in wild birds in Shanghai from 2020 to 2023, a total of nine H9N2 viruses were identified. To better understand the genetic characteristics of these H9N2 viruses in Shanghai, the whole genome sequences were analyzed. Phylogenetical analysis showed that the nine H9N2 viruses have undergone complicated reassortment with waterfowl viruses along the East Asian-Australasian flyways . The nine H9N2 viruses were classified into seven genotypes , and some of them could contribute internal genes to recently circulating HPAI A( H5N8 ) and A( H5N1 ) viruses of clade 2.3.4.4b. These results highlight the importance of active surveillance of AIVs in wild birds to comprehend viral ecology and evaluate potential transmission risk in poultry and humans. Source: Poultry Sciences,  https://www.sciencedirect.com/science/article/pi...

{Excerpt} Dear Editor, The highly pathogenic avian influenza viruses (HPAIVs) are important epizootic and zoonotic pathogens that cause significant economic losses to the poultry industry and pose a serious risk to veterinary and public health . Wild birds have been recognized as the primary reservoirs for influenza A virus, and some species show little sign of clinical disease or even can be asymptomatic during long distance carriers of the virus (Lycett et al., 2019). Since it was first discovered in 1959, the H5Nx HPAIVs have spread globally and cause outbreaks in wild birds, poultry and sporadic human and other mammalian infections (Lycett et al., 2019). Due to the reassortant events of diverse strains facilitated by migratory waterfowl, the clade 2.3.4.4 of H5Nx viruses acquiring neuraminidase (NA) gene from other low pathogenicity avian influenza viruses (LPAIVs) emerged in 2014 and gradually became the dominant sub-clade (Lee et al., 2017). The genetic diversity of clade 2.3.4.4...

Abstract Influenza is a major infectious disease challenge affecting animal and human health globally, and wild birds are historically the primary reservoirs of all the known Influenza A virus subtypes. Here, we detected the Highly Pathogenic Avian Influenza (HPAI) virus in exotic and aquatic birds in three different locations in Nigeria. On the 8th of February 2021, exotic birds: Yellow Golden Pheasant (Chrysolophus pictus), Sultan chicken (Gallus gallus domesticus), Lakenvelder chicken (Gallus gallus domesticus), and Common pheasant (Phasianus calchicus), imported from Libya and transported across the Niger Republic border to Nigeria, were presented to the National Veterinary Research Institute, Vom, for screening. Also, a family in Lagos State bought some exotic aquatic birds from a live bird market in Sokoto State , Nigeria, where sudden death was recorded with the birds showing few clinical signs. Similarly, the sudden death of some aquatic birds was reported in Mandela Parks and ...