clinicohistopathological diagnosis of infectious laryngotracheitis in broiler flocks: first report in fars province

Infectious laryngotracheitis (ilt) is a highly contagious viral respiratory disease in chickens caused by gallid alphaherpesvirus-1, primarily affecting the upper respiratory tract and leading to symptoms such as coughing, gasping, nasal discharge, and conjunctivitis. this study reports the first confirmed case of ilt in broilers through histopathological examination in the fars province of iran. a 40-day-old broiler flock of 45000 birds, housed in three halls, was referred to the avian specialty clinic. one hall, containing 15000 birds, exhibited respiratory symptoms such as sneezing, and ocular/nasal discharge, with a daily mortality increase from 60 to 90 birds over five days. necropsy of several affected chickens revealed firm caseous exudate in the larynx with diphtheritic membranes adhering to the mucosa of the upper trachea associated with mild hemorrhage. tracheal samples were fixed in 10% neutral buffered formalin for microscopic assessment. histopathological examination of tracheal mucosa revealed lymphocytic and histiocytic infiltration, epithelial cells necrosis, loss of goblet cells, hemorrhage, fibrinonecrotic exudates, syncytial cells, and presence of eosinophilic intranuclear inclusion bodies surrounded by a halo in epithelial and syncytial cells. based on clinical and histopathological findings, the disease was diagnosed as ilt. in conclusion, ilt was diagnosed in broilers of the fars province and may contribute to respiratory disease complexes. therefore, rapid diagnosis, alongside other confirmatory diagnostic tests is essential. to prevent the spread of the disease, broiler breeder flocks should not be sourced from regions where pullets have been vaccinated. the best approach to control the disease in broiler chickens is to maintain strict biosecurity measures.