author(s)
Tamilmaran P, Kumar R, Lakkawar AW, Uma S and Nair MG

abstract
Infectious laryngotracheitis (ILT) is a viral disease of the respiratory tract of chicken that occur in areas where there is intensive poultry production and responsible for severe economic losses. The present study was aimed to investigate the occurrence and pathology of infectious laryngotracheitis in commercial layer chicken in Namakkal, Tami Nadu and Puducherry. Out 62 commercial layer farms investigated in the present study, 40 (64.5%) were identified as positive for ILT. The occurrence of ILT varied from 4 to 70 weeks of age. Birds between the age group of 10 to 20 weeks were more affected and the mortality rate ranged from 1% to 17%. In layers, the mortality varied from 1% to 6% with production loss of 12%. The disease was prevalent throughout the year and the course of the disease extended for 30 days. Clinically, dullness, reduced feed and water intake, respiratory distress gasping, coughing up blood or blood tinged mucus and pump handle-type respiration was observed. Grossly trachea revealed catarrhal, haemorrahgic and/or necrotic changes. Histopathological examination revealed degeneration of tracheal epithelium, hyperplasia with syncytial formation, complete necrosis and infiltration by inflammatory cells. Occasionally, intranuclear inclusion bodies in the epithelial cells, cystic dilation of submucosal gland and lymphoid aggregations were noticed.