Experimental Study on the Pathogenicity of Avian Influenza A/Ch/It/5093/99(H7N1) Virus in Chicken

Abstract

In this study, the pathogenicity of A/Ch/It/5093/1999 H7N1 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 1-5 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 (2-5 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 48 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/5093/99 died between 2d.p.i and 5 d.p.i. (2-5 d.p.i). On day 1 to 3 d.p.i. relatively high titer of infectious virus could also be isolated from oropharyngeal swab 102.3 to105.9 50% egg infectious doses (EID50/ml), whereas virus shedding from the cloaca (101.5 to 103.2 EID50/ml) was considerably less. The present study was conducted to determine the pathogenicity of A/Ch/It/5093 H7N1 in chickens. In our data show that infection of chicken with H7N1 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.