Characaterization of H5N1 highly pathogenic avian influenza viruses isolated from poultry in Pakistan 2006-2008

Authors: Wasilenko, Jamie; Pantin Jackwood, Mary; KHAN, TASEET AHMED - Sindh Poultry Vaccine Center; AHMED, AYAZ - Sindh Poultry Vaccine Center; REHMANI, SHAFQAT - Sindh Poultry Vaccine Center; LONE, NAZIR AHMED - Sindh Poultry Vaccine Center; Swayne, David; Spackman, Erica

Submitted to: Virus Genes
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/31/2011
Publication Date: 11/16/2011
Citation: Wasilenko, J.L., Pantin Jackwood, M.J., Khan, T., Ahmed, A., Rehmani, S., Lone, N., Swayne, D.E., Spackman, E. 2012. Characaterization of H5N1 highly pathogenic avian influenza viruses isolated from poultry in Pakistan 2006-2008. Virus Genes. 44:247-52.

Interpretive Summary: Highly virulence forms of avian influenza virus can be found in poultry world-wide; however, the Asian H5N1 strain is among the most deadly. Because this strain is common in Asia and the Middle East it is critical to understand the epidemiology of the virus. Characterizing avian influenza virus from outbreaks in poultry can also provide critical information on how the virus is evolving, which helps to keep vaccines effective by updating them when needed. In this report some H5N1 avian influenza viruses from Pakistan were genetically characterized to determine the source of the outbreak and to determine if there are any notable mutations. It was determined that there was one introduction of H5N1 into Pakistan for the period of 2006- through 2008. H5N1 has not been reported since 2008 in Pakistan. The source of the virus appears to be local as the viruses are closely related to viruses from India and Bangladesh. No unusual mutations were observed in these isolates. Monitoring and characterization of avian influenza virus will continue in the region.

Technical Abstract: Nine avian influenza viruses (AIV), H5N1 subtype, were isolated from dead poultry in the Karachi region of Pakistan from 2006-2008. The intravenous pathogenicity indices and HA protein cleavage sites of all nine viruses were consistent with highly pathogenic AIV. Based on phylogenetic analysis of the HA genes these isolates belong to clade 2.2 and both the HA and NA are closely related to each other (nucleotide identities above 99.0%) and to other Middle Eastern H5N1 AIV isolates (nucleotide identities above 98.0%). The phylogenetic data suggest that the virus in both epornitics of H5N1 HPAIV in commercial poultry in the Karachi region of Pakistan between 2006 and 2008 were from a very closely related source, however there is inadequate epidemiological data to determine what the reservoir was for the virus between the 2006 and 2007 outbreaks other than that there was a single introduction into the region.