Since March 2007, an epidemic of highly pathogenic avian influenza have been devastating in backyard and commercial poultry in Bangladesh. The agents were pathotyped as highly pathogenic H5N1. This investigation reports the result of a retrospective investigation of an outbreak of low pathogenic H9N2 avian influenza in commercial parent stock chickens that occurred in 2006. The morbidity and mortality were 50% and 3%, respectively during 2–3 months. The egg production decreased to 36% and hatchability reduced to 10%. The clinical signs included less feed and water intake, nasal and ocular discharges and severe respiratory distress. On postmortem, samples including larynx, trachea and lungs were collected in 10% neutral buffered formalin and tracheal swabs, larynx and tracheal tissues were collected in Falcon tube containing 50% buffered glycerin with antibiotic and stored frozen at -70 °C. Histopathology was conducted using routine procedure. RNA extraction and RT-PCR were done using Qiagen RNA extraction and one step RT-PCR kits. Grossly, hemorrhage in nasal septum, sinuses, eyelids, larynx and trachea were found. Lungs were congested. Histologically, in larynx and trachea loss of mucosal epithelium, hemorrhages and mononuclear cells infiltration in lamina propria, blood tinged exudates in laryngeal and tracheal lumen were observed. In few cases, goblet cells were hypertrophied and mucosal glands were prominent that formed cystic spaces. RT-PCR confirmed the presence of 245 bp product of matrix protein gene and 488 bp fragment of H9 subtype specific haemagglutinin gene as well as 244 bp fragments of N2 gene in the suspected samples.The study proved that H9N2 low pathogenic avian influenza virus was introduced in Bangladesh before the detection of H5N1 viruses.
Low pathogenic, avian influenza, RT-PCR