Prevalence And Pathology Of Chronic Respiratory Disease In Broilers

The study was conducted to determine the prevalence and pathology of Chronic Respiratory Disease (CRD) in broilers. Broiler carcasses (n=339) were examined for the gross lesions suggestive of chronic respiratory disease of which 36 birds (10.61%) had lesions strongly suggestive of CRD. Sixty pooled swab samples from nostrils, choanal cleft, trachea and air sacs were collected from broilers affected with respiratory infections and processed for Polymerase Chain Reaction (PCR). The overall prevalence of Mycoplasma gallisepticum (MG) in broilers with respiratory lesions was determined as 13.33% by PCR. Amongst these, 75% of birds found positive for MG were less than three weeks of age and 25% of samples positive for MG were from birds of seven to eight weeks of age. Microscopically, the histopathological findings noticed in the PCR positive CRD in trachea were hyperaemia, surface epithelial destruction, mucous gland hypertrophy, haemorrhage, mucosal thickening, infiltration of leukocytes and squamous cell metaplasia. Histopathological observations in lungs include congestion, haemorrhage, infiltration of cells, oedema, septal thickening, secondary bronchial mucosal hyperplasia, necrosis and denudation and respiratory atrial muscle thickening.