|Pusch, Elizabeth - Orise Fellow|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 4/9/2018
Publication Date: 4/15/2018
Citation: Suarez, D.L., Pusch, E. 2018. The under appreciated threat of H9N2 avian influenza [abstract]. 10th International Symposium on Avian Influenza, Brighton, United Kingdon, April 15-18, 2018. p.74.
Technical Abstract: The H9N2 subtype of avian influenza is commonly found in wild birds and occasionally spreads to poultry. When comparing viruses recently introduced into poultry using a standard transmission model (5 SPF chickens are infected at different doses, and 2 days later 3 naïve contact control birds are added to the cage) viruses recently introduced to poultry from wild birds require high challenge doses and transmit poorly. However, when recent viruses from Asia or the Middle East are tested in the same model, the infectious dose is much lower and the virus is more transmissible. Three unique and unrelated lineages of H9N2 have been circulating in poultry for over 20 years, and the transmission model shows these viruses are now highly adapted to chickens. Although the H9N2 viruses remain low pathogenic in pathotyping studies, in the field all three lineages are reported to cause respiratory disease, often with a decrease in egg laying and increased mortality in unvaccinated flocks, particularly when the flocks are infected with other respiratory pathogens. Because of the serious disease caused by these viruses, vaccination is commonly used as a control measure. However, both field reports and Hemagglutination Inhibition (HI) studies show that antigenic drift is a serious concern and reports of clinical disease in vaccinated flocks is being reported. In particular the G1 lineage has become the most widespread and is endemic in many Asian, Middle Eastern, and African countries. It was just reported in sub-Saharan Africa for the first time. H9N2 is also known to cause a zoonotic infection. A renewed focus on control of H9N2 is needed for this group of viruses.