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. 2023 Dec;12(2):e2252510.
doi: 10.1080/22221751.2023.2252510. Epub 2023 Aug 25.

Emergence of a new genotype of clade 2.3.4.4b H5N1 highly pathogenic avian influenza A viruses in Bangladesh

Subrata Barman  1 , Jasmine C M Turner  1 , M Kamrul Hasan  2 , Sharmin Akhtar  2 , Trushar Jeevan  1 , John Franks  1 , David Walker  1 , Nabanita Mukherjee  1 , Patrick Seiler  1 , Lisa Kercher  1 , Pamela McKenzie  1 , Robert G Webster  1 , Mohammed M Feeroz  2 , Richard J Webby  1
Affiliations

Emergence of a new genotype of clade 2.3.4.4b H5N1 highly pathogenic avian influenza A viruses in Bangladesh

Subrata Barman et al. Emerg Microbes Infect. 2023 Dec.

Abstract

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.

Keywords: Bangladesh; Surveillance; Tanguar Haor; avian influenza A virus; clade 2.3.4.4b H5N1; domestic ducks; migratory birds; reassortment.

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Conflict of interest statement

No potential conflict of interest was reported by the author(s).

Figures

Figure 1.
Figure 1.
Migratory bird flyways and AIV sample collection sites in Bangladesh. There are nine major flyways around the world [6]. Two major flyways for migratory birds that intersect in Bangladesh, the Central Asian (green) and East Asian-Australian (red) flyways. Oropharygeal and cloacal samples from free range ducks (14 farms) and fecal samples from wild birds (10 locations) were collected from Tanguar Haor wetland areas. Oropharyngeal, cloacal, and water-trough samples were collected from poultry and poultry cages at 4 LPMs (three in Dhaka and one near Dhaka), Bangladesh.
Figure 2.
Figure 2.
Avian influenza A viruses isolated in Bangladesh. (A) Monthly virus isolation from Tanguar Haor. On January, February, and December 2021, 1000, 1000, and 1010 virologic samples, respectively, were collected from free range ducks and migratory waterfowl at Tangua Hoar. No viruses were isolated on January and February. On December the sole H7N7 (blue) and four H5N1 viruses of clade 2.3.4.4b (pink) were isolated from Tanguar Haor. (B) Monthly virus isolation from Bangladeshi LPMs. On February, August, September, October, and December 2021, every month, 160 virologic samples were collected from poultry and poultry cages at 4 LPMs in or near Dhaka, Bangladesh. (C) Viruses isolated from the samples collected from, or environmental samples associated with, different species of birds in LPMs.
Figure 3.
Figure 3.
Phylogenetic relationship of the HA genes of the HPAI H5N1 viruses isolated in Bangladesh. The viruses identified in this study are shown in colour (red, clade 2.3.2.1a H5N1 viruses isolated from LPMs; pink, clade 2.3.4.4b H5N1 viruses isolated from Tanguar Haor). BD, Bangladesh; *, Reference antigens used for clade 2.3.2.1a viruses HI assays. **, Reference antigens used for clade 2.3.4.4b viruses HI assays. Tree is rooted to A/goose/Guangdong/1/96(H5N1). Bootstrap values ≥70 are shown on branches.
Figure 4.
Figure 4.
Phylogenetic relationship of the NA genes of the HPAI H5N1 viruses isolated in Bangladesh. The viruses identified in this study are shown in colour (red, clade 2.3.2.1a H5N1 viruses isolated from LPMs; pink, clade 2.3.4.4b H5N1 viruses isolated from Tanguar Haor). BD, Bangladesh. Tree is rooted to A/goose/Guangdong/1/96(H5N1). Bootstrap values ≥70 are shown on branches.
Figure 5.
Figure 5.
Phylogenetic relationship of the PB2 genes of the viruses isolated in Bangladesh. The viruses identified in this study are shown in colour (red, clade 2.3.2.1a H5N1; pink, clade 2.3.4.4b H5N1; green, H9N2; and blue, non-H9N2 LPAI viruses). BD, Bangladesh; Nds, Netherlands. Tree is rooted to A/equine/Prague/1/1956(H7N7). Bootstrap values ≥70 are shown on branches.
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