The pathobiology of H7N3 low and high pathogenicity avian influenza viruses from the United States outbreak in 2020 differs between turkeys and chickens

Authors: CRIADO, MIRIA - Consultant; LEYSON, CHRISTINA - Orise Fellow; YOUK, SUNGSU - Orise Fellow; Deblois, Suzanne; Olivier, Timothy; KILLIAN, MARY - Animal And Plant Health Inspection Service (APHIS); TORCHETTI, MIA - Animal And Plant Health Inspection Service (APHIS); PARRIS, DARREN - Orise Fellow; Spackman, Erica; Kapczynski, Darrell; Suarez, David; Swayne, David; Pantin Jackwood, Mary

Submitted to: Viruses
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/10/2021
Publication Date: 9/16/2021
Citation: Criado, M.F., Leyson, C.M., Youk, S., Deblois, S.M., Olivier, T.L., Killian, M.L., Torchetti, M.L., Parris, D.J., Spackman, E., Kapczynski, D.R., Suarez, D.L., Swayne, D.E., Pantin Jackwood, M.J. 2021. The pathobiology of H7N3 low and high pathogenicity avian influenza viruses from the United States outbreak in 2020 differs between turkeys and chickens. Viruses. 13(9):1851. https://doi.org/10.3390/v13091851.
DOI: https://doi.org/10.3390/v13091851

Interpretive Summary: High pathogenicity avian influenza viruses (HPAIVs) remain a threat to poultry worldwide. An outbreak caused by H7N3 subtype of low pathogenicity avian influenza virus (LPAIV) and HPAIV occurred in turkey farms in North Carolina and South Carolina in 2020. The disease caused by these viruses was examined in turkeys and chickens. High infectivity and transmission were observed with the LPAIV and HPAIV in turkeys; but a higher dose of the viruses was required to infect chickens, and the viruses transmitted poorly in this species. These results show clear differences in the pathobiology of avian influenza viruses in chickens and turkeys and corroborate the high susceptibility of turkeys to both LPAIV and HPAIV infections.

Technical Abstract: An outbreak caused by H7N3 low pathogenicity avian influenza virus (LPAIV) occurred in commercial turkey farms in the states of North Carolina (NC) and South Carolina (SC), United States in March of 2020. Subsequently, H7N3 high pathogenicity avian influenza virus (HPAIV) was detected on a turkey farm in SC. The infectivity, transmissibility, and pathogenicity of the H7N3 HPAIV and two LPAIV isolates, including one with a deletion in the neuraminidase (NA) protein stalk, were studied in turkeys and chickens. High infectivity [<2 log10 50% bird infectious dose (BID50)] and transmission to birds exposed by direct contact were observed with the HPAIV in turkeys. In contrast, the HPAIV dose to infect chickens was higher than for turkeys (3.7 log10 BID50), and no transmission was observed. Similarly, higher infectivity (<2–2.5 log10 BID50) and transmissibility were observed with the H7N3 LPAIVs in turkeys compared to chickens, which required higher virus doses to become infected (5.4–5.7 log10 BID50). The LPAIV with the NA stalk deletion was more infectious in turkeys but did not have enhanced infectivity in chickens. These results show clear differences in the pathobiology of AIVs in turkeys and chickens and corroborate the high susceptibility of turkeys to both LPAIV and HPAIV infections.