Detection and Molecular Characterization of Avibacterium paragallinarum from Poultry

Background: Infectious coryza is an acute, highly contagious respiratory disease of chickens caused by Avibacterium paragallinarum causing heavy economical loss to the poultry farmers. The laboratory diagnosis of Av. paragallinarum infection is based mainly on conventional methods such as isolation and identification of the organisms. In modern poultry industry, the rapid diagnosis of Av. paragallinarum is essential along with detection of variation among the serotypes. Methods: A total of 128 samples (viz., heart blood swabs, tracheal, eye and infra orbital swabs) suspected for infectious coryza were screened for the presence of Av. paragallinarum by isolation and molecular characterization. Information regarding farm/flock strength, age of birds, method of rearing, production performance, clinical symptoms manifested and mortality patterns from various organized poultry farms were recorded. A total of five isolates of Av. paragallinarum have been recovered from suspected materials processed for isolation. Two isolates were sequenced and analysed. Result: All the isolates showed same biochemical characters but exhibited variability in the fermentation of mannose, mannitol and sorbitol. The nucleotide variation of Av. paragallinarum present in Indian subcontinent differs in their virulence and pathogenicity. The study was also focused for the molecular characterisation of Avibacterium species from different isolates. Though the clinical signs and gross pathological signs were similar, the nucleotide variation between isolates was observed. Sequencing of ‘hagA’ gene showed that the two isolates were closely related to the strains of China, Australia, Mexico and India which shared 94-100% homology.