Experimental Study on the Pathogenicity of Avian Influenza A/Ch/It/۵۰۹۳/۹۹(H۷N۱) Virus in Chicken

In this study, the pathogenicity of A/Ch/It/۵۰۹۳/۱۹۹۹ H۷N۱ which had been isolated from chicken during the outbreak in Italy was assessed in chicken by experimental infection virus. Ten SPF chickens of four week-old were inoculated with this virus, and five chickens were inoculated with uninfected allantoic fluid. For determination of virus shedding, oropharyngeal and cloacal swabs were taken from experiment and control groups, on days ۱-۵ post infection (p.i.) and used in a reverse transcription-polymerase chain reaction (RT- PCR) assay for detection of avian influenza virus (AIV). On day (۲-۵ d.p.i.) certain organs such as lung, brain, liver and kidneys collected from dead birds for virus titration, and histopathological investigations. In this study we obtained high titers in oropharyngeal swabs in ۴۸ hours p.i. (h.p.i.). The first clinical signs observed were anorexia and depression in chickens. The results obtained with the virus isolation were confirmed by RT-PCR. All of the chickens inoculated with A/Ch/It/۵۰۹۳/۹۹ died between ۲d.p.i and ۵ d.p.i. (۲-۵ d.p.i). On day ۱ to ۳ d.p.i. relatively high titer of infectious virus could also be isolated from oropharyngeal swab ۱۰۲.۳ to۱۰۵.۹ ۵۰% egg infectious doses (EID۵۰/ml), whereas virus shedding from the cloaca (۱۰۱.۵ to ۱۰۳.۲ EID۵۰/ml) was considerably less. The present study was conducted to determine the pathogenicity of A/Ch/It/۵۰۹۳ H۷N۱ in chickens. In our data show that infection of chicken with H۷N۱ virus leads to viral replication on the respiratory tract resulting in severe lung damage. The most consistent and severely affected organ by this virus were lung, kidney and brain, severity of the lesions in each organ was probably related to tissue tropism.

Keywords:

Avian Influenza , H۷N۱ , pathogenicity , Chicken