Novel variants of clade 2.3.4 highly pathogenic avian influenza A(H5N1) viruses, China.
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ABSTRACT:
SUBMITTER: Gu M
PROVIDER: S-EPMC3840869 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Highly pathogenic avian influenza (HPAI) subtype H5N1 clade 2.3.4.4b virus has spread globally, causing unprecedented large-scale avian influenza outbreaks since 2020. In 2021, we isolated 17 highly pathogenic avian influenza H5N1 viruses from wild birds in China. To determine virus origin, we genetically analyzed 1,529 clade 2.3.4.4b H5N1 viruses reported globally since October 2020 and found that they formed 35 genotypes. The 17 viruses belonged to genotypes G07, which originated from eastern Asia, and G10, which originated from Russia. The viruses were moderately pathogenic in mice but were highly lethal in ducks. The viruses were in the same antigenic cluster as the current vaccine strain (H5-Re14) used in China. In chickens, the H5/H7 trivalent vaccine provided complete protection against clade 2.3.4.4b H5N1 virus challenge. Our data indicate that vaccination is an effective strategy for preventing and controlling the globally prevalent clade 2.3.4.4b H5N1 virus.
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Project description:Among the diverse clades of highly pathogenic avian influenza (HPAI) H5N1 viruses of the goose/Guangdong lineage, only a few have been able to spread across continents: clade 2.2 viruses spread from China to Europe and into Africa in 2005-2006, clade 2.3.2.1 viruses spread from China to Eastern Europe in 2009-2010 and clade 2.3.4.4 viruses of the H5Nx subtype spread from China to Europe and North America in 2014/2015. While the poultry trade and wild-bird migration have been implicated in the spread of HPAI H5N1 viruses, it has been proposed that robust virus-shedding by wild ducks in the absence of overt clinical signs may have contributed to the wider dissemination of the clade 2.2, 2.3.2.1 and 2.3.4.4 viruses. Here we determined the phenotype of two divergent viruses from clade 2.3.2.1, a clade that spread widely, and two divergent viruses from clade 2.3.4, a clade that was constrained to Southeast Asia, in young (ducklings) and adult (juvenile) mallard ducks. We found that the virus-shedding magnitude and duration, transmission pattern and pathogenicity of the viruses in young and adult mallard ducks were largely independent of the virus clade. A clade-specific pattern could only be detected in terms of cumulative virus shedding, which was higher with clade 2.3.2.1 than with clade 2.3.4 viruses in juvenile mallards, but not in ducklings. The ability of clade 2.3.2.1c A/common buzzard/Bulgaria/38?WB/2010-like viruses to spread cross-continentally may, therefore, have been strain-specific or independent of phenotype in wild ducks.
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Project description:Asian lineage A/H5N1 highly pathogenic avian influenza viruses (HPAIVs) have been responsible for continuous outbreaks in Bangladesh since 2007. Although clades 2.2.2 and 2.3.4.2 HPAIVs have disappeared since poultry vaccination was introduced in 2012, clade 2.3.2.1a viruses have continued to be detected in Bangladesh. In this study, we identified A/H9N2 (n = 15), A/H5N1 (n = 19), and A/H5N1-A/H9N2 (n = 18) mixed viruses from live bird markets, chicken farms, and wild house crows (Corvus splendens) in Bangladesh from 2016 to 2018. We analyzed the genetic sequences of the H5 HPAIVs, to better understand the evolutionary history of clade 2.3.2.1a viruses in Bangladesh. Although seven HA genetic subgroups (B1-B7) and six genotypes (G1, G1.1, G1.2, G2, G2.1, and G2.2) have been identified in Bangladesh, only subgroup B7 and genotypes G2, G2.1, and G2.2 were detected after 2016. The replacement of G1 genotype by G2 in Bangladesh was possibly due to vaccination and viral competition in duck populations. Initially, genetic diversity decreased after introduction of vaccination in 2012, but in 2015, genetic diversity increased and was associated with the emergence of genotype G2. Our phylodynamic analysis suggests that domestic Anseriformes, including ducks and geese, may have played a major role in persistence, spread, evolution, and genotype replacement of clade 2.3.2.1a HPAIVs in Bangladesh. Thus, improvements in biosecurity and monitoring of domestic Anseriformes are needed for more effective control of HPAI in Bangladesh.
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Project description:Influenza virological surveillance was conducted in Bangladesh from January to December 2021 in live poultry markets (LPMs) and in Tanguar Haor, a wetland region where domestic ducks have frequent contact with migratory birds. The predominant viruses circulating in LPMs were low pathogenic avian influenza (LPAI) H9N2 and clade 2.3.2.1a highly pathogenic avian influenza (HPAI) H5N1 viruses. Additional LPAIs were found in both LPM (H4N6) and Tanguar Haor wetlands (H7N7). Genetic analyses of these LPAIs strongly suggested long-distance movement of viruses along the Central Asian migratory bird flyway. We also detected a novel clade 2.3.4.4b H5N1 virus from ducks in free-range farms in Tanguar Haor that was similar to viruses first detected in October 2020 in The Netherlands but with a different PB2. Identification of clade 2.3.4.4b HPAI H5N1 viruses in Tanguar Haor provides continued support of the role of migratory birds in transboundary movement of influenza A viruses (IAV), including HPAI viruses. Domestic ducks in free range farm in wetland areas, like Tangua Haor, serve as a conduit for the introduction of LPAI and HPAI viruses into Bangladesh. Clade 2.3.4.4b viruses have dominated in many regions of the world since mid-2021, and it remains to be seen if these viruses will replace the endemic clade 2.3.2.1a H5N1 viruses in Bangladesh.
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Project description:Highly pathogenic H5N1 and low pathogenic H9N2 influenza viruses are endemic to poultry markets in Bangladesh and have cocirculated since 2008. H9N2 influenza viruses circulated constantly in the poultry markets, whereas highly pathogenic H5N1 viruses occurred sporadically, with peaks of activity in cooler months. Thirty highly pathogenic H5N1 influenza viruses isolated from poultry were characterized by antigenic, molecular, and phylogenetic analyses. Highly pathogenic H5N1 influenza viruses from clades 2.2.2 and 2.3.2.1 were isolated from live bird markets only. Phylogenetic analysis of the 30 H5N1 isolates revealed multiple introductions of H5N1 influenza viruses in Bangladesh. There was no reassortment between the local H9N2 influenza viruses and H5N1 genotype, despite their prolonged cocirculation. However, we detected two reassortant H5N1 viruses, carrying the M gene from the Chinese H9N2 lineage, which briefly circulated in the Bangladesh poultry markets and then disappeared. On the other hand, interclade reassortment occurred within H5N1 lineages and played a role in the genesis of the currently dominant H5N1 viruses in Bangladesh. Few 'human-like' mutations in H5N1 may account for the limited number of human cases. Antigenically, clade 2.3.2.1 H5N1 viruses in Bangladesh have evolved since their introduction and are currently mainly homogenous, and show evidence of recent antigenic drift. Although reassortants containing H9N2 genes were detected in live poultry markets in Bangladesh, these reassortants failed to supplant the dominant H5N1 lineage.
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