Vol. 7, Issue 4, Part B (2025)

Infectious laryngotracheitis (ILT) is a re-emerging, acute respiratory disease in chicken in various parts of the country including Tamil Nadu, leading to production losses. The present study was conducted to detect and confirm the pathogen associated with mortality among commercial and native chickens in five different flocks in and around Salem district of Tamil Nadu. On necropsy examination, haemorrhagic tracheitis and caseous plugs were noticed along the trachea and no other gross abnormalities were observed. Tracheal samples from the dead birds were collected for laboratory investigation. The suspected field samples were screened positive by PCR targeting the ILTV-ICP4 gene. Virus isolation was performed in 9-11 days old embryonated chicken eggs via chorioallantoic membrane (CAM) route and thickened, haemorrhagic membranes were observed after five days post-infection, with pock lesions. The infected CAM during the serial egg-passages were also found positive for ILTV by PCR. Histopathological examination revealed the presence of pathognomonic syncytia with eosinophilic inclusion bodies in the respiratory tract epithelium and profuse infiltration of heterophils and mononuclear cells along the submucosa, followed by necrosis and deciliation. This study confirmed the presence of ILT in both commercial and native chicken flocks by molecular, histopathological analyses and virus isolation studies, warranting the need for continuous surveillance and improved vaccines for disease control.