Pathogenicity study of field isolates of Avibacterium paragallinarum in experimentally infected birds

Infectious coryza (IC), caused by Avibacterium paragallinarum, is an infectious and highly contagious disease among the primary bacterial respiratory disease of poultry. Reports regarding pathogenicity studies of the Indian isolates of this important poultry pathogen are limited. The present paper reports the pathogenicity study of the field isolates of Av. paragallinarum in experimentally infected birds. A total of 28 birds of seven week old age were randomly divided into 3 experimental groups – Group I (n=16), II (n=8) and III (n=4). Four birds each of the Group-I and II were infected separately with the four field isolates and two reference isolates of Av. paragallinarum, respectively. Birds of Group-III were kept as uninfected control. An inoculum of 0.2 ml (1011 CFU/ml viable bacteria) was given to the chicks through intranasal and infraorbital sinus route of each isolate for three days. All the infected birds were examined daily for 7–10 days for clinical symptoms and progression of the disease. All the four field isolates of Av. paragallinarum were found to be pathogenic exhibiting typical clinical signs and histopathological lesions of infectious coryza. The causative bacterium Av. paragallinarumwas re-isolated from nasal and infraorbital sinus cavity exudates after 3rd day and 7th day of infection.