Role of domestic ducks in the emergence of a new genotype of highly pathogenic H5N1 avian influenza A viruses in Bangladesh

Abstract

Highly pathogenic avian influenza H5N1 viruses were first isolated in Bangladesh in February 2007. Subsequently, clades 2.2.2, 2.3.4.2 and 2.3.2.1a were identified in Bangladesh, and our previous surveillance data revealed that by the end of 2014, the circulating viruses exclusively comprised clade 2.3.2.1a. We recently determined the status of circulating avian influenza viruses in Bangladesh by conducting surveillance of live poultry markets and waterfowl in wetland areas from February 2015 through February 2016. Until April 2015, clade 2.3.2.1a persisted without any change in genotype. However, in June 2015, we identified a new genotype of H5N1 viruses, clade 2.3.2.1a, which quickly became predominant. These newly emerged H5N1 viruses contained the hemagglutinin, neuraminidase and matrix genes of circulating 2.3.2.1a Bangladeshi H5N1 viruses and five other genes of low pathogenic Eurasian-lineage avian influenza A viruses. Some of these internal genes were closely related to those of low pathogenic viruses isolated from ducks in free-range farms and wild birds in a wetland region of northeastern Bangladesh, where commercially raised domestic ducks have frequent contact with migratory birds. These findings indicate that migratory birds of the Central Asian flyway and domestic ducks in the free-range farms in Tanguar haor-like wetlands played an important role in the emergence of this novel genotype of highly pathogenic H5N1 viruses.

Emerging Microbes & Infections (2017) 6, e72; doi:10.1038/emi.2017.60; published online 9 August 2017

Keyword:

• avian influenza A virus
• domestic duck
• migratory bird
• reassortment
• surveillance

Acknowledgments

We thank the following people at St Jude Children’s Research Hospital for their contributions to this work: Richard Elia and Jerry Parker for technological support and assistance with database maintenance; James Knowles for administrative assistance; and Nisha Badders for editing this manuscript. We are thankful to Dr Sajeda Begum and Ashis Kumar Datta of Department of Zoology, Jahangirnagar University for their support during sample collection. We also acknowledge the originating and submitting laboratories of the sequences from the Global Initiative on Sharing All Influenza Data (GISAID) EpiFlu Database (www.gisaid.org) that were used in this study. This work was funded by the National Institute of Allergy and Infectious Diseases (HHSN272201400006C) and ALSAC.

Supplementary Information for this article can be found on the Emerging Microbes & Infections website (http://www.nature.com/emi)