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Title: Impact of route of exposure and challenge dose on the pathogenesis of H7N9 low pathogenicity avian influenza virus in chickens

Author
item Spackman, Erica
item Pantin Jackwood, Mary
item Swayne, David
item Suarez, David
item Kapczynski, Darrell

Submitted to: Virology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/14/2015
Publication Date: 2/6/2015
Publication URL: https://handle.nal.usda.gov/10113/60566
Citation: Spackman, E., Pantin Jackwood, M.J., Swayne, D.E., Suarez, D.L., Kapczynski, D.R. 2015. Impact of route of exposure and challenge dose on the pathogenesis of H7N9 low pathogenicity avian influenza virus in chickens. Virology. 477:72-81.

Interpretive Summary: A new strain of flu, called H7N9, emerged in humans in China in early 2013. Based on the genetics of the virus and investigations of the cases, many of which had contact with live bird markets, there was speculation that poultry or other birds were the source of the virus. Therefore we conducted studies in order to determine if chickens can play a role in maintaining the virus in the environment. We found that the virus caused no disease in chickens; chickens could be infected with no outward signs. However a large amount of virus was needed to even infect chickens, which indicates that the virus may not be well adapted to chickens and that there may be other factors involved in the maintenance of the H7N9 influenza in live bird markets in China.

Technical Abstract: H7N9 influenza A first caused human infections, often with severe disease, in early 2013 in China. Virus genetics, histories of patient exposures to poultry, and previous experimental studies all point to the source of the virus being a domestic avian species, such as chickens. In order to better understand the ecology of this H7N9 in chickens, we evaluated the infectious dose and pathogenesis of A/Anhui/1/2013 H7N9 in two common breeds of chickens, White Leghorns (table-egg layers) and White Plymouth Rocks (meat chickens). No morbidity or mortality were observed with doses of 1,000,000 or 100,000,000 50% egg infectious doses per bird when administered by the upper respiratory route. Challenge experiments with three other human origin H7N9 viruses showed a similar pattern of virus replication. At 1,000,000 mean infectious doses per bird, the infectious dose for chickens was higher than expected for a chicken adapted virus, suggesting that chickens may not be the most efficient reservoir.