Study on pathogenesis of low pathogenic avian influenza virus H9 in broiler chickens.

Abstract

Avian influenza viruses (AIV) are placed in the family of Orthomyxoviridae having three influenza genera known as A, B and C. The viruses which are responsible for infections in birds, belongs to genus influenza virus A which can produce two different types of diseases on bases of their virulence and pathogenicity viz., highly pathogenic avian influenza virus (HPAIV) and a low pathogenic avian influenza virus (LPAIV). Frequent outbreaks of LPAIV H9N2 in Asian countries such as in Pakistan and China revealed that this subtype has become endemic in poultry industry. In this study pathogenesis of virus H9 has been studied in broiler chickens under field for which, challenge strains (H9 virus was isolated from field samples and experimental inocula were prepared for study of pathogenesis of H9 virus out under controlled environmental conditions. The virus prevailing in Pakistan was found non pathogenic with Intravenous Pathogenicity Index (IVPI) 0.12/3, produced significant reduction in body weight and had tissue tropism for kidney and respiratory system. Immunohistochemical detection of viral antigen and rapid molecular detection of virus from tissues by using Reverse Transcriptase Polymerase Chain Reaction (RT-PCR) revealed that RT-PCR is efficient method than immunohistochemistry. In conclusion, the virus subtype H9 circulating in Pakistan is low pathogenic in nature with affinity for respiratory system and urinary system in broiler chickens.