Submitted to: Archives of Virology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/10/2010
Publication Date: 1/1/2011
Publication URL: http://handle.nal.usda.gov/10113/60725
Citation: Wasilenko, J.L., Arafa, A.M., Selim, A.A., Hassan, M.K., Aly, M.M., Ali, A., Nassif, S., Elebiary, E., Balish, A., Klimov, A., Suarez, D.L., Swayne, D.E., Pantin Jackwood, M.J. 2011. Pathogenicity of two Egyptian H5N1 highly pathogenic avian influenza viruses in domestic ducks. Archives of Virology. 156(1):37-51. Interpretive Summary: Highly pathogenic avian influenza (HPAI) viruses of the H5N1 subtype remain an economic threat to commercial poultry throughout the world by negatively impacting animal health and trade. Domestic ducks have been implicated in the spreading of H5N1 HPAI viruses. Ducks infected with HPAI viruses usually don't show signs of disease. However recent strains of the Asian H5N1 avian influenza viruses have shown to produce clinical signs and mortality in ducks. In this study, two H5N1 HPAI viruses originating from Egypt in 2007 and 2008, were used to infect domestic Pekin ducks. Both viruses produced clinical signs and mortality, but the 2008 virus was more virulent, killing the ducks earlier and producing more neurological signs in ducks than the 2007 virus. Differences in virus genes between the two viruses, that might explain the differences observed in pathogenicity, were examined. Gene sequences were similar between these two viruses; however, the hemagglutinin gene had 16 amino acid differences, changes that might contribute to the differences in pathogenicity observed. In conclusion, and similar to what has been seen in some Asian countries, the Egyptian H5N1 HPAI viruses has increased in ducks.
Technical Abstract: Domestic ducks have been implicated in the dissemination and evolution of H5N1 highly pathogenic avian influenza (HPAI) viruses. Interestingly, the pathogenicity of H5N1 HPAI viruses in domestic ducks has increased over time with some viruses producing 100% mortality in ducks. These changes in virulence have been reported in viruses from Asian countries with high population of domestic ducks. In this study, two H5N1 HPAI viruses originating from Egypt in 2007 and 2008, were analyzed to determine the pathogenicity of these viruses in domestic ducks (Anas platyrhynchos). Both viruses produced clinical signs and mortality, but the 2008 virus was more virulent, inducing earlier onset of neurological signs and killing all ducks with a mean death time (MDT) of 4.5 days. The 2007 virus killed 3 of 8 ducks with a mean death time of 7 days. Full genome sequencing and phylogenetic analysis was carried out in order to examine differences in virus genes that might explain the differences observed in pathogenicity. Both Egyptian viruses belong to clade 2.2.1, which contains other Egyptian and Middle Eastern virus isolates. Gene sequences were similar between these two viruses; however, the hemagglutinin gene had 16 amino acid differences, changes that might contribute to the differences in pathogenicity observed between these two viruses. In conclusion, and similar to what has been seen in some Asian countries, the pathogenicity of Egyptian H5N1 HPAI viruses has increased in ducks, indicating virus adaptation through continuous virus circulation in domestic duck populations.