The low pathogenic avian influenza (LPAI) H9N2 virus became endemic in Egypt since 2011 and causing several losses in commercial poultry flocks either broilers, layers or broilers breeders flocks. The disease always present in complication with other pathogens either viral pathogen as Infectious bronchitis virus, Newcastle disease virus, infectious laryngeotrachitis
virus or bacterial pathogen as Escherichia coli, Ornithobacterium and mycoplasma species. The aim of this work was to monitor the tissue tropism of the LPAI H9N2 virus in different bird tissues and check the proper organs to detect and isolate the virus on time manner interval in addition to check the pathogenicity of recent isolated LPAI H9N2 virus. The study
has been done on one hundred SPF one-day old chicks and a recent isolated H9N2 virus used for challenge. The results of this study showed that, the H9N2 still low pathogenic and could not cause mortalities as a sole pathogen. The virus, could be detect starting from the 2nd to 11th day post infection on different birds' tissues. In conclusion, the H9N2 virus has
pneumotropic, nephrotropic and viscerotropic properties and could be detected on those tissues in addition to some lymphoid tissue. The virus could be isolated starting from the 2nd day PI from respiratory organs and until 11th day post-infection (PI) from the kidney tissues and the highest virus load in the birds' tissues was in respiratory organs and cecal tonsils at the 3-5 days PI.
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