Submitted to: Virus Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/26/2009
Publication Date: 5/15/2009
Citation: Pfeiffer, J., Pantin Jackwood, M.J., To, T.L., Nguyen, T., Suarez, D.L. 2009. Phylogenetic and biological characterization of highly pathogenic H5N1 avian influenza viruses (Vietnam 2005) in chickens and ducks virus research. Virus Research. 142:108-120. Interpretive Summary: Highly pathogenic avian influenza causes a severe and often fatal disease in chickens and turkeys. The Asian H5N1 strain of highly pathogenic avian influenza has become the most widespread form of the virus and is found on three continents. The country of Vietnam first reported Asian H5N1 in their country in 2004, and the virus has become endemic in poultry in the country since then. This study describes viruses isolated from Vietnam from December of 2005. These viruses were not only highly pathogenic for chickens, but they were also highly pathogenic for ducks, which until recently was unusual. Genetically the viruses could be divided into two separate groups. The viruses appeared to be most similar to other viruses reported from mainland China. The surveillance and characterization of avian viruses are important to aid our controlling these infections.
Technical Abstract: Analysis of Asian H5N1 avian influenza (AI) virus hemagglutinin (HA) genes shows a common origin, but the virus has evolved into at least three major clades (clades 0, 1, and 2) over the last 11 years. Previous reports of Vietnam viruses have documented predominantly clade 1 viruses. Unexpectedly, 19 viruses isolated from northern Vietnam isolated in December 2005 fell into clade 2. These viruses further clustered into two distinct sublineages. Representative viruses from each sublineage were chosen for antigenic and pathogenic evaluation. Two distinct antigenic groups correlating with the genetic information were present when comparing hemagglutination inhibition (HI) titers. All viruses were highly virulent not only in chickens, killing them within two days of experimental inoculation, but also in two-week old Pekin ducks, causing 100% mortality within four days of challenge. The information gained about these viruses provides insight with regards to implementing control programs, including vaccine seed strain selection.