|LEYSON, CHRISTINA - ORISE FELLOW|
|YOUK, SUNG-SU - ORISE FELLOW|
|DIMITROV, KIRIL - CONSULTANT|
|LEE, DONG-HUN - ORISE FELLOW|
|LARSEN, LARS ERIK - TECHNICAL UNIVERSITY OF DENMARK|
Submitted to: Virology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/20/2019
Publication Date: 8/22/2019
Citation: Leyson, C., Youk, S., Smith, D.M., Dimitrov, K., Lee, D., Larsen, L., Swayne, D.E., Pantin Jackwood, M.J. 2019. Pathogenicity and genomic changes of a 2016 European H5N8 highly pathogenic avian influenza virus (clade 220.127.116.11) in experimentally infected mallards and chickens. Virology. 537:172-185. https://doi.org/10.1016/j.virol.2019.08.020.
Interpretive Summary: Highly pathogenic avian influenza (HPAI) viruses remain a threat to poultry worldwide. HPAI viruses of the subtype H5N8, clade 18.104.22.168B. caused outbreaks in poultry and unusually high mortality in wild birds in Europe, the Middle East, and Africa in 2016-2017. In this study we examined the disease caused by of one of the virus from these outbreaks in mallards and chickens. In mallards, high mortality and transmission were observed in the groups inoculated with moderate to high doses of the virus. As expected with a HPAI virus, high mortality occurred in infected chickens but a high dose of the virus was required to infect them and no transmission to contacts was observed, indicating that the virus was better adapted to mallards. To examine for changes in the virus genome as the virus replicated in the two different avian hosts, full virus genomes were obtained from the bird samples (swabs and tissues). Viral sequences from the chicken samples had a higher number of changes but lower genetic diversity compared to viral sequences from mallard samples, which is consistent with virus population bottlenecks occurring when infecting and replicating in a host for which it is not well adapted to. In conclusion, differences in viral fitness and virus genetic changes were observed between mallards and chickens infected with the H5N8 HPAI virus examined.
Technical Abstract: Highly pathogenic avian influenza H5N8 clade 22.214.171.124 virus caused outbreaks in poultry and unusually high mortality in wild birds in 2016–2017. The pathobiology of one of these viruses was examined in mallards and chickens. High mortality and transmission to direct contacts were observed in mallards inoculated with medium and high doses of the virus. However, in chickens, high mortality occurred only when birds are given the high virus dose and no transmission was observed, indicating that the virus was better adapted to mallards. In comparison with the virus inoculum, viral sequences obtained from the chickens had a higher number of nucleotide changes but lower intra-host genomic diversity than viral sequences obtained from the mallards. These observations are consistent with population bottlenecks occurring when viruses infect and replicate in a host that it is not well adapted to. Whether these observations apply to influenza viruses in general remains to be determined.