The pathogenesis of clade 2.3.4.4 H5 highly pathogenic avian influenza viruses in Ruddy Ducks (Oxyura jamaicensis) and Lesser Scaup (Aythya affinis)

Authors: Spackman, Erica; PROSSER, DIANN - Us Geological Survey (USGS); Pantin Jackwood, Mary; BERLIN, ALICIA - Us Geological Survey (USGS); STEPHENS, CRISTOPHER - Orise Fellow

Submitted to: Journal of Wildlife Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/5/2017
Publication Date: 4/6/2017
Publication URL: https://handle.nal.usda.gov/10113/5763047
Citation: Spackman, E., Prosser, D., Pantin Jackwood, M.J., Berlin, A., Stephens, C.B. 2017. The pathogenesis of clade 2.3.4.4 H5 highly pathogenic avian influenza viruses in Ruddy Ducks (Oxyura jamaicensis) and Lesser Scaup (Aythya affinis). Journal of Wildlife Diseases. 53(4):1-11. doi:10.7589/2017-01-003.

Interpretive Summary: Ducks represent diverse species of waterfowl which have a variety of feeding strategies and habitats. One broad classification of ducks is based on how the ducks feed in bodies of water: dabbling ducks feed near the surface and do not submerge and diving ducks submerge and seek food in deeper water. Most work with avian influenza virus (AIV) has focused on dabbling ducks because they are plentiful, targeted by hunters and are proven natural hosts for AIV. Typically AIV does not cause any disease in dabbling ducks, but they can be infected and excrete high levels of virus, thus spreading the virus. In contrast, very little information is available for the susceptibility of diving ducks for AIV. Here we investigated whether 2 common North American species of diving ducks (Ruddy Duck and Lesser Scaup) can be infected with AIV. Similar to dabbling ducks, the Ruddy Ducks and Lesser Scaup could be infected with AIV, but did not get sick. Therefore these species may also be involved in the natural maintenance and dissemination of AIV.

Technical Abstract: Waterfowl are the natural hosts of avian influenza virus (AIV) and disseminate the virus worldwide through migration. Historically, surveillance and research efforts for AIV in waterfowl have focused on dabbling ducks. The role of diving ducks in AIV ecology has not been well characterized. In this study, we examined the relative susceptibility and pathogenicity of clade 2.3.4.4 H5 highly pathogenic (HP) AIV (HPAIV) in two species of diving ducks. Juvenile and adult Ruddy Duck (Oxyura jamaicensis) and juvenile Lesser Scaup (Aythya affinis) were intranasally inoculated with A/Northern Pintail/WA/40964/2014 H5N2 HPAIV. Additional groups of juvenile Lesser Scaups were inoculated with A/Gyrfalcon/WA/41088/2014 H5N8 HPAIV. The approximate 50% bird infectious doses (BID50) of the H5N2 isolate for adult Ruddy Ducks was ,102 50% egg infectious doses (EID50) and for the juvenile Lesser Scaups it was ,104 EID50. There were insufficient juvenile Ruddy Ducks to calculate the BID50. The BID50 for the juvenile Lesser Scaups inoculated with the H5N8 isolate was 103 EID50. Clinical disease was not observed in any group; however, mortality occurred in the juvenile Ruddy Ducks inoculated with the H5N2 virus (three of five ducks), and staining for AIV antigen was observed in numerous tissues from these ducks. One adult Ruddy Duck also died and although it was infected with AIV (the duck was positive for virus shedding and AIV antigen was detected in tissues), it was also infected with coccidiosis. The proportion of ducks shedding virus was related to the dose administered, but the titers were similar among dose groups. The group with the fewest ducks shedding virus was the adult Ruddy Ducks. There was a trend for the Lesser Scaups to shed higher titers of virus than the Ruddy Ducks. No virus shedding was detected after 7 d postinoculation in any group. Similar to dabbling ducks, Lesser Scaups and Ruddy Ducks are susceptible to infection with this H5 HPAIV lineage, although they excrete lower titers of virus.