Pathological and Molecular Studies on Avian Influenza Virus (H9N2) in Broilers

Background and Objective: Avian influenza viruses (AIV) subtype H9 is a low pathogenic virus that usually causes low mortality in the broiler birds. In this study, serotype H9N2 was screened in broiler farms showing mild respiratory manifestations in Dakahlia province, Egypt during the period from October, 2014 to January, 2015. Materials and Methods: H9N2 virus was isolated from only 4 broiler farms out of 25 by real time polymerase chain reaction (RT-PCR). Phylogenetic analysis of the haemagglutinin gene (HA) showed that the isolates were grouped in Quail/Hong Kong/G1/97 lineage-strains similar to the one circulating in the Middle East. Specific pathogenic free-embryonated chicken embryo (SPF-ECE) was inoculated with PCR-positively infected materials on allantoic cavity. Histopathological examination was followed by immunohistochemistry staining of H9 virus in formalin fixed paraffin-embedded and frozen tissue specimens. Results: By immunohistochemistry, the virus was stained in trachea, lungs and kidneys of broiler chickens, in liver and intestine of inoculated chicken embryos. Conclusion: Site of replication of the H9N2 virus in tissues differed in broilers from that in embryos. However, the virus was low pathogenic in nature, the use of biosecurity measures by poultry farmers in Egypt is recommended to avoid outbreaks.