Policy Statement:
Removal of Live Bird Lethality Testing Requirement

Date: February 2, 2018

Subject: Removal of Live Bird Lethality Testing Requirement for Pathogenicity Testing of Reverse Genetically Derived Viruses for Avian Influenza Viruses


The Division of Agricultural Select Agents and Toxins (DASAT) regulates the possession, use, and transfer of biological agents listed in 7 C.F.R. Part 331 and 9 C.F.R. Part 121 that have the potential to pose a severe threat to animal or plant health or animal or plant products (select agents and toxins).


DASAT received requests to remove the requirement* for live bird lethality testing used to determine the pathogenicity characteristics of reverse genetically derived viruses, for avian influenza viruses that undergo a manipulation process that alters the pathogenicity of the virus from high to low.

Policy Statement:

DASAT will accept reassortant virus exclusion requests absent of live bird lethality testing data for avian influenza constructs in which:

  • the backbone strain is a PR8 or similar human vaccine strain previously demonstrated to have limited to no replication in poultry, regardless of the HA gene; and
  • the H5/H7 cleavage site has been altered from highly pathogenic avian influenza (HPAI) to low pathogenic avian influenza (LPAI); and
  • viruses used for gene inserts have been well characterized as LPAI prior to use in reverse genetically derived processes.

In lieu of the live bird lethality testing, DASAT will require all reverse genetically derived H5/H7 viruses with PR8 or similar human vaccine strain backbone to:

  • Confirm by genetic sequencing that the amino acid sequence at the HA cleavage site is compatible with only LPAI viruses; and
  • Demonstrate functionality as a LPAI virus either by cell culture system with/without exogenous trypsin, or in-vivo test in chickens by the intravenous pathogenicity index (IVPI) per World Organisation for Animal Health (OIE) standards.
Page last reviewed: January 12, 2021, 01:35 PM