Submitted to: European Scientific Working Group on Influenza
Publication Type: Abstract only
Publication Acceptance Date: 6/2/2002
Publication Date: 10/20/2002
Citation: Suarez, D.L., Spackman, E. 2002. Control of H7N2 influenza in the live bird markets in the northeast united states. European Scientific Working Group on Influenza. Interpretive Summary:
Technical Abstract: Since 1994 H7N2 avian influenza has been endemic in the live bird market system in the northeast United States. The live bird markets (LBMs) are primarily in and around the New York City area and they sell a wide variety of poultry, primarily to specific ethnic markets. Current regulatory efforts have so far been ineffective at eradicating the virus from the markets. The molecular epidemiology of the influenza outbreaks have shown that a single introduction of the H7 gene has been the predominant isolate in the market, but evidence of additional introductions of other H7 viruses have also been observed, although these isolates have not persisted in the market system. The hemagglutinin gene is rapidly evolving and has a high rate of amino acid substitutions, including several changes at the hemagglutinin cleavage site and a 8 amino acid deletion in the HA1 portion of the hemagglutinin protein. The changes at the HA cleavage site included a T>P substitution at the ¿2 position in 1995, a N>L change at the ¿5 position in 1998, and a P>L change at the ¿2 position in 2002. Each of these changes has eventually replaced the parent population except for the most recent change. The last cleavage site change has resulted in four out of 5 amino acids at the cleavage site being basic, which is dangerously close to making the virus highly pathogenic for poultry. However, the virus when tested using the standard animal pathotyping test has demonstrated the virus is still mildly pathogenic. Evidence of widespread reassortment of the nonstructural and matrix gene segments was observed during the first three years of the outbreak, but after 1998 a single lineage of both genes became predominant in the market. In an effort to control the outbreak, a three day mandatory market closure was planned. In support of the market closure a real time RT-PCR assay was developed to allow faster determination if birds in the markets became reinfected and to aid in traceback testing. This RT-PCR test was recently compared to virus isolation using clinical samples from a recent epidemiological study of the LBMs. An update on the success of the eradication effort will be presented as well as an evaluation of the effectiveness of the rapid RT-PCR test in aiding the control efforts.