The pathogenesis of H5Nx clade 2.3.4.4 group A highly pathogenic avian influenza virus in surf scoters (Melanitta perspicillata)

Authors: LUCZO, JASMINA - Oak Ridge Institute For Science And Education (ORISE); PROSSER, DIANN - Us Geological Survey (USGS); Pantin Jackwood, Mary; BERLIN, ALICIA - Us Geological Survey (USGS); Spackman, Erica

Submitted to: BioMed Central (BMC) Veterinary Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/16/2020
Publication Date: 9/28/2020
Publication URL: https://handle.nal.usda.gov/10113/7125842
Citation: Luczo, J., Prosser, D., Pantin Jackwood, M.J., Berlin, A., Spackman, E. 2020. The pathogenesis of H5Nx clade 2.3.4.4 group A highly pathogenic avian influenza virus in surf scoters (Melanitta perspicillata). BioMed Central (BMC) Veterinary Research. 16:351. https://doi.org/10.1186/s12917-020-02579-x.
DOI: https://doi.org/10.1186/s12917-020-02579-x

Interpretive Summary: Some species of waterfowl are known to be silent carriers of virulent strains of bird flu, which are deadly for chickens and turkeys. Surveys of wild ducks have found the non-virulent form of bird flu in most species of ducks that have been tested, but it is not known if these species can also carry the virulent form. Surf scoters are a North American diving duck which winters in coastal waters, but breeds in Alaska and Northern Canada, which are the same areas as most North American ducks. Therefore could have contact with ducks that are known to carry bird flu. To determine if surf scoters can silently carry virulent bird flu like other ducks, scoters were exposed to the virus. All ducks were infected, but disease was mostly very mild (mild lethargy for about 24hrs). Two elderly ducks were more severly effected, but were also naturally infected with another common duck virus. Importantly, the scoters excreted high quantities of virus for 10 days. Surf scoters could act as silent carries of bird flu.

Technical Abstract: Aquatic waterfowl, particularly those in the order Anseriformes and Charadriiformes, are the ecological reservoir of avian influenza viruses (AIVs). Dabbling ducks play a recognized role in the maintenance and transmission of AIVs. Furthermore, the pathogenesis of highly pathogenic AIV (HPAIV) in dabbling ducks is well characterized. In contrast, the role of diving ducks in HPAIV maintenance and transmission remains unclear. In this study, the pathogenesis of a North American clade 2.3.4.4 Gs/Gd/96-lineage H5Nx HPAIV, A/Northern pintail/Washington/40964/2014 (H5N2), in diving sea ducks (surf scoters, Melanitta perspicillata), was characterized. Intrachoanal inoculation of surf scoters with clade 2.3.4.4 HPAIV induced mild transient clinical disease, however ducks were concomitantly shedding high virus titers, particularly from the oropharyngeal route. Two aged ducks that succumbed to HPAIV infection had pathological evidence for co-infection with duck virus enteritis, which was confirmed by molecular approaches. Widespread HPAIV antigen was observed in visceral and central nervous system organs, and was associated with histopathological lesions. Collectively, surf scoters, are susceptible to HPAIV infection and excrete high titers of HPAIV from the respiratory and cloacal tracts whilst being asymptomatic. The susceptibility of diving sea ducks to H5 HPAIV highlights the need for additional research and surveillance to further understand the contribution of diving ducks to HPAIV ecology.