An avian influenza virus A (H7N9) reassortant that recently emerged in the United States with low and highly pathogenic phenotype does not efficiently infect swine

Authors: POWELL, JOSHUA - Orise Fellow; Abente, Eugenio; TORCHETTI, MIA - Animal And Plant Health Inspection Service (APHIS); KILLIAN, MARY - Animal And Plant Health Inspection Service (APHIS); Baker, Amy

Submitted to: Influenza and Other Respiratory Viruses
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/18/2018
Publication Date: 2/13/2019
Citation: Powell, J.D., Abente, E.J., Torchetti, M.K., Killian, M.L., Vincent, A.L. 2019. An avian influenza virus A (H7N9) reassortant that recently emerged in the United States with low pathogenic phenotype does not efficiently infect swine. Influenza and Other Respiratory Viruses. 13:288-291. https//doi.org/10.1111/irv.12631.
DOI: https://doi.org/10.1111/irv.12631

Interpretive Summary: Influenza A virus (IAV) is an important pathogen in humans, pigs, and birds, among other species, and IAV strains that are adapted to one species can sporadically infect a different species and cause outbreaks. There is a potential risk of avian viruses from wild birds spilling over into swine due to overlap between pig production systems and major bird migration flyways, as well as pig and poultry production regions. In Spring of 2017, a novel avian-origin H7N9 virus was detected in poultry in Tennessee, Georgia, Alabama, and Kentucky and caused significant economic loss. In an experimental challenge study, we were unable to detect virus in the lungs or in the nasal cavity, and there was no evidence of pig-to-pig transmission. These findings suggest that there is a low probability that the avian-origin H7N9 could be sustained in the pig population without substantial evolutionary changes to the genetics of the virus.

Technical Abstract: In 2017, outbreaks of low and highly pathogenic avian H7N9 viruses were reported in four States in the USA. In total over 270,000 birds died or were culled, causing significant economic loss. The potential for avian-to-swine transmission of the U.S. avian H7N9 was unknown. In an experimental challenge in swine using a representative low pathogenic H7N9 (A/chicken/Tennessee/17-007431-3/2017; LPAI TN/17) isolated from these events, no infectious virus in the upper or lower respiratory tract was detected, nor was lung pathology or evidence of transmission in pigs observed, indicating that the virus cannot efficiently infect swine.