|STEPHENS, CHRIS - Orise Fellow|
|BERTRAN-DOLS, KATERI - Consultant|
Submitted to: PLoS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/25/2017
Publication Date: 5/8/2017
Citation: Pantin Jackwood, M.J., Stephens, C., Bertran-Dols, K., Swayne, D.E., Spackman, E. 2017. The pathogenesis of H7N8 low and highly pathogenic avian influenza viruses from the United States 2016 outbreak in chickens, turkeys and mallards. PLoS One. 12(5):1-21. doi:10.1371/journal.pone.0177265.
Interpretive Summary: In January of 2016, a turkey flock was discovered to be infected with a new type of virulent bird flu. A few other flocks were found to have been infected with a non-virulent form, which likely came from wild birds. The outbreak was rapidly controlled with only 9 affected flocks. Both forms of the bird flu were tested for their ability to infect chickens, turkeys and mallards in order to better understand how the virus got into the turkeys and spread among domestic poultry. It was observed that the turkeys were the most susceptible to infection and the chickens were the most resistant. Also, the more virulent form, which seems to have emerged in one turkey flock could more easily infect all three species than the non-virulent form. The course of infection was different among the species as well. The turkeys were most severely affected, the chickens were less so and the ducks did not experience any disease. This supports that the evolution in turkeys resulted in virus that was better adapted to the species evaluated.
Technical Abstract: In January 2016, a combined outbreak of highly pathogenic (HP) avian influenza virus (AIV) and low pathogenicity (LP) AIV occurred in commercial turkeys in the state of Indiana, United States. Genetically, the viruses were highly similar, belonged to the North American wild bird lineage, and had not been previously detected in poultry. In order to understand the pathobiology of the H7N8 LPAIV and HPAIV, infectivity, transmission and pathogenicity studies were conducted in chickens, turkeys, and mallards. Among the three species the lowest mean infectious dose for both the LP and HP phenotype was for turkeys, and also disease from the LPAIV was only observed with turkeys. Furthermore, although the HPAIV was lethal for both chickens and turkeys, clinical signs caused by the HPAIV isolate differed between the two species; neurological signs were only observed in turkeys. Mallards could be infected with and transmit both viruses to contacts, but neither caused clinical disease. Interestingly, with all three species, the mean infectious dose of the HP isolate was at least ten times lower than that of the LP isolate. This study corroborates the high susceptibility of turkeys to AIV as well as a pathobiology that is different from chickens. Further, this study demonstrates that mallards can be asymptomatically infected with HP and LP AIV from gallinaceous poultry and may not just be involved in transmitting AIV to them.