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Title: Lack of chicken adaptation of newly emergent Eurasian H5N8 and reassortant H5N2 high pathogenicity avian influenza viruses in the U.S. is consistent with restricted poultry outbreaks in the Pacific flyway during 2014-2015

Author
item BERTRAN, KATERI - Consultant
item Swayne, David
item Pantin Jackwood, Mary
item Kapczynski, Darrell
item Spackman, Erica
item Suarez, David

Submitted to: Virology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/15/2016
Publication Date: 4/26/2016
Publication URL: http://handle.nal.usda.gov/10113/62895
Citation: Bertran, K., Swayne, D.E., Pantin Jackwood, M.J., Kapczynski, D.R., Spackman, E., Suarez, D.L. 2016. Lack of chicken adaptation of newly emergent Eurasian H5N8 and reassortant H5N2 high pathogenicity avian influenza viruses in the U.S. is consistent with restricted poultry outbreaks in the Pacific flyway during 2014-2015. Virology. 494:190-197. https://doi.org/10.1016/j.virol.2016.04.019.
DOI: https://doi.org/10.1016/j.virol.2016.04.019

Interpretive Summary: In 2014-2015 the United States experienced the largest outbreak of highly pathogenic avian influenza that it had ever experienced. Infected birds were detected in over 20 states and over 48 million birds died or were euthanized to control the outbreak. This manuscript describes the experimental inoculation of two early representative viruses in chickens to understand more about how the virus makes birds sick and how easily the virus transmits from bird to bird. The results show that the virus was deadly in the birds that it infected, but it took a large amount of virus to infect each chicken. The virus also transmitted poorly from infected chicken to uninfected chicken. This data supports the idea that the virus was present in wild birds and these wild birds could on some occasions transmit the virus to both backyard and commercial poultry. Once the virus got onto a large commercial poultry farm, the virus did seem to adapt to become more infectious for chickens. This data will be helpful to devise better control measures for prevention of the introduction of the virus.

Technical Abstract: In 2014-2015, the U.S. experienced an unprecedented outbreak of Eurasian clade 2.3.4.4 H5 highly pathogenic avian influenza (HPAI) virus, initially affecting mainly wild birds and few backyard and commercial poultry premises. To better model the outbreak, the pathogenesis and transmission dynamics of representative Eurasian H5N8 and reassortant H5N2 clade 2.3.4.4 HPAI viruses detected early in the North American outbreak were investigated in chickens. High mean chicken infectious doses and lack of seroconversion in survivors indicated the viruses were poorly chicken adapted. Pathobiological features were consistent with HPAI virus infection, although the delayed appearance of lesions, longer mean death times, and reduced replication in endothelial cells differed from features of most other Eurasian H5N1 HPAI viruses. Although these initial U.S. H5 HPAI viruses had reduced adaptation and transmissibility in chickens, multi-generational passage in poultry could generate poultry adapted viruses with higher infectivity and transmissibility.