Occurrence of Avian Influenza Virus (H9 subtype) in Broiler and Layer Chickens at Sharkia Governorate

Document Type : Original Article

Authors

1 Reference Laboratory for Quality Control on Poultry Production (RLQP). Animal Health Research Institute, Sharkia Branch, Egypt

2 Avian and Rabbit Medicine Department, Faculty of Veterinary Medicine, Zagazig University, 44511, Egypt

3 Reference Laboratory for Quality Control on Poultry Production (RLQP), Animal Health Research Institute, Ismailia Branch, Egypt

Abstract

Avian influenza (AI) is a contagious disease caused by type A influenza viruses. In spite of the mild nature of H9N2 low pathogenic AIV, the virus was isolated from frequent disease outbreaks with high mortality in different parts of the world. In this study, forty-two layer and broiler chicken farms (21/each) suspected to be infected with AIV of different breeds and ages during 2012 - 2014 were examined at Sharkia Governorate. The occurrence of AI in chickens using HI assay was 40.47%. Subtyping for H9 and H5 subtypes has been done by specific antisera. The H9 was detected in 30.95% and H5 was 9.52%. However, the occurrence of NDV in chickens was 23.80%. The selected seven AIV isolates representing broiler and layer flocks were confirmed by rRT-PCR using primers and probes specific for Matrix gene, H9 gene, H5 gene and H7 gene. Seven isolates were positive for M. gene indicating AI virus detection, and then 6 out of 7 isolates were positive for H9 gene but negative for H5 and H7 genes. The last isolate was positive for H5 gene, negative for H9 and H7 genes.  The phylogenetic analysis for HA gene of the Six H9 AIV isolates showed the placement of the Egyptian viruses within the same lineage of H9N2 viruses that circulated in the region with the parent strain (A/Quail/ Egypt/ 113413v/2011) of G1/97 lineage and other strains that circulating in the Middle East.The circulating H9N2 AIV genetic analysis is pointing to a minor evolution of H9N2 viruses. But at the same time the co-circulation of H5 & H9 subtypes of AIV could be a risk for emergence of new AI viruses. Also, concurrent infection with viral (IBV and NDV) as well as bacterial agents (MG, Salmonella and E. coli) are considered the main cause behind increased mortality in H9N2 positive flocks.

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