Abstract

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.

中文翻译：

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孟加拉国 2.3.2.1a 高致病性禽流感 A/H5N1 病毒进化枝的遗传进化和传播动态

摘要

自 2007 年以来，亚洲谱系 A/H5N1 高致病性禽流感病毒 (HPAIV) 一直是孟加拉国持续爆发的原因。尽管自 2012 年引入家禽疫苗接种以来，进化枝 2.2.2 和 2.3.4.2 HPAIV 已经消失，但进化枝 2.3.2.1a 病毒在孟加拉国继续被发现。在本研究中，我们 从活禽市场、养鸡场和野屋中鉴定了 A/H9N2 ( n  = 15)、A/H5N1 ( n  = 19) 和 A/H5N1-A/H9N2 ( n = 18) 混合病毒乌鸦 ( Corvus splendens) 于 2016 年至 2018 年在孟加拉国。我们分析了 H5 HPAIV 的基因序列，以更好地了解孟加拉国进化枝 2.3.2.1a 病毒的进化历史。尽管在孟加拉国已经确定了七个 HA 遗传亚群 (B1-B7) 和六个基因型 (G1、G1.1、G1.2、G2、G2.1 和 G2.2)，但只有亚群 B7 和基因型 G2、G2。 2016年后检测到G2.1和G2.2。孟加拉国G1基因型被G2取代可能是由于鸭群的疫苗接种和病毒竞争。最初，在 2012 年引入疫苗接种后，遗传多样性下降，但在 2015 年，遗传多样性增加并与基因型 G2 的出现有关。我们的系统动力学分析表明，包括鸭和鹅在内的家养 Anseriformes 可能在持久性、传播、进化、和基因型替换进化枝 2.3.2.1a HPAIV 在孟加拉国。因此，需要改进生物安全和国内 Anseriformes 的监测，以更有效地控制孟加拉国的高致病性禽流感。