Abstract
Infectious coryza (IC) is a severe upper respiratory tract disease of birds. This research was aimed to study different aspects of Avibacterium paragallinarum causing IC in commercial birds. A total of 1000 samples were collected from IC suspected or recently dead birds. Results showed that 80.40% of the samples were positive for A. paragallinarum. All the isolates of A. paragallinarum produced the predicted size of 500 bp amplicons of HPG2 gene on PCR. The percentages of positive samples infected with infectious coryza in commercial birds were: 19.2% for layers, 18.4% for broilers, 16.0% for quails, 15.8% for chukars and 11.0% for pigeons. Among positive cases, serotype A was 24%, serotype B was 29% and serotype C was 27.40%. The isolates of A. paragallinarum were growing well at 35-37 degrees C, however, growth rate was declined at 24 degrees C, and 42 degrees C. Similarly, A. paragallinarum showed optimal growth between pH 5 and 9, but the superlative pH growth values were from 6 to 8 pH. Antimicrobial susceptibility test showed that all tested isolates displayed resistance against Metronidazole, Colistin sulphate, Bacitracin, Streptomycin, Chloramphenicol and Lincomycine, while they were found susceptible to Tetracycline, Erythromycin, Vancomycin, Amoxicillin, and Ciprofloxacin. Investigation of IC in commercial birds will certainly help the diagnosis of the disease, which causes considerable economic loss to the farmers. The current study was designed to report on the incidence of IC caused A. paragallinarum, frequency of occurrence of its serotypes and drug susceptibility pattern. This study will also alert poultry professionals about the disease and help determine specific medication as well as formulate prevention and control strategies.