Isolation of infectious laryngotracheitis virus in broiler chicken in Iran: First report

In February 2019, a severe respiratory distress with co-infection of infectious laryngotracheitis (ILT) and Newcastle disease accompanied with Salmonella Enteritidis occurred in a broiler flock in the western region of Iran. Clinical signs included paralysis, torticollis, nasal discharge, conjunctivitis, gasping and respiratory rale with high mortality. At necropsy, caseous diphtheritic membrane adherent to the larynx and trachea was observed. Microscopically, syncytial cells formation with dense eosinophilic intranuclear inclusion bodies were main histopathological findings in tracheal tissues. Conventional polymerase chain reaction (PCR) for ICP4 gene amplification as a definitive diagnosis was utilized for the detection of ILT virus nucleic acid in suspected tracheal samples inoculated on to the chorioallantioc membrane of 11-day-old specific pathogen free (SPF) chicken eggs. Tracheal tissues taken from these SPF birds were positive by nested ILT PCR. In conclusion, because of no vaccination policy against ILT in broilers, the most probable scenario is that virus-laden dust or other fomites can be vectors and virus persistence and disease outbreak can be a sequel of wild virus introduction to the farm.