Tropism of Highly Pathogenic Avian Influenza H5 Viruses from the 2020/2021 Epizootic in Wild Ducks and Geese

Abstract

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, contributed to the successful adaptation of 2020/2021 HPAI H5 viruses to wild waterbird populations.

Highly pathogenic avian influenza H5N1 virus infections in wild red foxes (Vulpes vulpes) show neurotropism and adaptive virus mutations

“…Neurological symptoms have also been reported for avian species. For example, HPAI disease in chickens is short and results in sudden death however, in domestic ducks and wild birds disease is longer and often neurological symptoms like partial paralysis and tremors can be observed (15)(16)(17). However, HPAI is generally considered to be a respiratory disease with high virus genomic RNA concentration in the respiratory system (18).…”

Avian influenza overview June – September 2022

“…The continuous and widespread circulation of HPAI A(H5) viruses in wild bird populations, and the increasing number of birds and wild bird species affected during the last two epidemic seasons indicate that HPAI A(H5) viruses are gradually adapting to the wild reservoir. It appears that HPAI A(H5) viruses can be maintained in the wild independently of domestic bird populations (Caliendo et al, 2022a). The high mortality in wild birds from HPAI virus in recent years has changed the paradigm of wild birds as unaffected agents of HPAI viruses, with increasing concerns about potential effects on their populations (Kleyheeg et al, 2017).…”

Avian influenza overview December 2021 – March 2022

“…These findings confirm subclinical natural infection with HPAI H5Nx GsGd viruses 2.3.4.4b in Eurasian teals and Eurasian wigeons, indicating that these species can act as long-distance vectors of these viruses, and that passive surveillance alone has a poor ability to identify the true level of HPAI virus infection in wild birds. Caliendo et al, (2022a; determined the virus distribution and associated pathological changes in five Eurasian wigeons, nine barnacle geese (Branta leucopsis) and 11 common buzzards (Buteo buteo) that died with HPAI H5N8 virus clade 2.3.4.4b infection during the 2020 HPAI season in the Netherlands. All animals were systemically infected and had encephalitis as well as necrosis in other organs including liver, pancreas and heart muscle.…”