author(s)
Chandravathi T, Rama Devi V, Satheesh K, Ravi Kumar P, Sudhakar K and Muralidhar M

abstract
Respiratory diseases have emerged as a great challenge to poultry industry and result in severe economic losses. Infectious coryza caused by Avibacterium paragallinarum (A. paragallinarum) affects upper respiratory tract. In the present study the pathological and molecular diagnosis of infectious coryza was carried out in commercial chicken from the Andhra Pradesh region. Samples were collected from the suspected birds of different poultry farms. Out of 20 pooled samples collected, 18 (90%) samples were found positive for infectious coryza by PCR, in which 2 samples were also found positive for E. coli on bacteriological examination. The affected birds showed respiratory symptoms like open mouth breathing, coughing, sneezing. Unilateral to bilateral edema of wattle and combs were observed in severely affected birds. In infectious coryza sinusitis, tracheitis, laryngitis, mild airsacculitis and pneumonia were noticed. In complicated cases of A. paragallinarum and E. coli severe sinusitis, tracheitis, laryngitis, airsacculitis, pneumonia, perihepatitis and pericarditis were noticed. From this study, it is concluded that PCR is an early, rapid, accurate and highly sensitive diagnostic technique which replace the conventional cultural examination and can be used as early diagnostic tool to prevent the economic losses associated with the disease.