Abstract
The surveillance and virological characterization of H5N8 avian influenza viruses are important in order to assess their zoonotic potential. The genetic analyses of the Egyptian H5N8 viruses isolated through active surveillance in wild birds and domestic poultry in the winter of 2016/2017 showed multiple introductions of reassortant viruses. In this study, we investigated and compared the growth kinetics, infectivity, and pathogenicity of the three reassortant forms of H5N8 viruses detected in wild birds and domestic poultry in Egypt during the first introduction wave in the winter of 2016/2017. Three representative H5N8 viruses (abbreviated as 813, 871, and 13666) were selected. The 871/H5N8 virus showed enhanced growth properties in vitro in Madin Darby canine kidney (MDCK) and A549 cells. Interestingly, all viruses replicated well in mice without prior adaptation. Infected C57BL/6 mice showed 20% mortality for 813/H5N8 and 60% mortality for 871/H5N8 and 13666/H5N8, which could be attributed to the genetic differences among the viruses. Studies on the pathogenicity in experimentally infected ducks revealed a range of pathogenic effects, with mortality rate ranging from 0% for 813/H5N8 and 13666/H5N8 to 28% for 871/H5N8. No significant differences were observed among the three compared viruses in infected chickens. Overall, different H5N8 viruses had variable biological characteristics, indicating a continuous need for surveillance and virus characterization efforts.
Highlights
Avian influenza viruses (AIVs) infect a wide range of avian species including domestic poultry and wild birds and exist in high pathogenic (HPAI) or low pathogenic (LPAI) forms [1,2]
Local Alignment Search Tool (BLASTN analysis indicated that three distinct genotypes were present in Egypt and that they were closely related to H5N8 viruses isolated from wild birds and poultry in Europe (Poland, Germany, Hungary, and Croatia), Russia, and Asia (India and Bangladesh) (Figure 2)
813 viruses and non-infected control group. These results clearly demonstrate the difference in the involvement characteristics evidence such of asthe incoordination, loss offorms balance, and A/H5N8 motor issues
Summary
Avian influenza viruses (AIVs) infect a wide range of avian species including domestic poultry and wild birds and exist in high pathogenic (HPAI) or low pathogenic (LPAI) forms [1,2]. HPAI viruses cause systemic infection and high mortality in poultry species and belong to either the H5 or H7 hemagglutinin (HA) subtypes. Since the detection of HPAI H5N1 subtype in 1996, the virus has evolved into 10 genetically defined clades (0 to 9) and numerous subclades based on the evolution of the hemagglutinin (HA) gene and has spread through four continents, affecting domestic poultry, wild birds, and mammals. Since late 2014, H5 clade 2.3.4.4 HPAI viruses have had a wide geographic dispersion, with movement from East Asia to North America, West Asia, Europe and Africa. Two distinct groups (group A and group B) of HPAI H5N8 viruses were characterized during massive outbreaks in the period from 2014 to 2016 [5]
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