H9N2 low pathogenic avian influenza: Should we be afraid?

Authors: Suarez, David

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 7/18/2017
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: The H9N2 low pathogenic avian influenza (LPAI) is probably the most widespread avian influenza subtype in poultry around the world being endemic in a large part of Asia, the Middle East, Northern Africa, and in Germany. Currently, there is no standardized clade system to describe the antigenic variation like we have for H5N1 highly pathogenic avian influenza, but the H9N2 lineages are more diverse than the H5N1 lineages. For example, Israel has two sublineages that differ by over 6 percent different at the amino acid level and differ by over 15% to H9N2 viruses from other countries. The H9N2 viruses in SPF chickens generally cause no or only minor disease, but in the field in combination with other respiratory pathogens and poor environmental conditions, severe disease with high mortality is commonly reported. Vaccines are commonly used to control the disease, but if the vaccines are not well matched to the field strain you may have poor protection. One feature that makes some of the lineages so unique is their ability to infect and transmit at very low doses. Experimental transmission studies in chickens show the infectious dose is below 10^2, showing that the viruses are highly adapted to poultry. Comparisons will be conducted of recent and historical H9N2 viruses for antigenic variation and transmissibility in chickens. The H9N2 viruses do pose a threat to U.S. poultry because of the disease threat and high transmissibility. Control efforts may be delayed because H9N2 is not a program disease.