Highly pathogenic avian influenza (HPAI) outbreaks have become increasingly frequent in wild bird populations and have caused mass mortality in many wild bird species. The 2020/2021 epizootic was the largest and most deadly ever reported in Europe, and many new bird species tested positive for HPAI virus for the first time. This study investigated the tropism of HPAI virus in wild birds. We tested the pattern of virus attachment of 2020 H5N8 virus to intestinal and respiratory tissues of key bird species; and characterized pathology of naturally infected Eurasian wigeons (Mareca penelope) and barnacle geese (Branta leucopsis). This study determined that 2020 H5N8 virus had a high level of attachment to the intestinal epithelium (enterotropism) of dabbling ducks and geese and retained attachment to airway epithelium (respirotropism). Natural HPAI 2020 H5 virus infection in Eurasian wigeons and barnacle geese also showed a high level of neurotropism, as both species presented with brain lesions that co-localized with virus antigen expression. We concluded that the combination of respirotropism, neurotropism, and possibly enterotropism, con-tributed to the successful adaptation of 2020/2021 HPAI H5 viruses to wild waterbird populations.
Bibliographical noteFunding Information:
This research was funded by the European Union?s Horizon 2020 research and innovation programme DELTAFLU, grant number 727922. Acknowledgments: We thank Peter van Run, Oanh Vuong, Rachel Scheuer and Theo Bestebroer for screening surveillance samples and associated lab work. We thank the pathology staff of Wa-geningen Bioveterinary Research for necropsy and sample collection of dead wild birds.
Funding: This research was funded by the European Union’s Horizon 2020 research and innovation programme DELTAFLU, grant number 727922.
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