Molecular and Pathological Investigations on Vaccinal and Field Strains of Infectious Laryngotracheitis Virus (ILTV) in Egypt

Abstract

This thesis was planned to describe the pathological lesions in respiratory tissue of chickens infected with ILTV. Apply different methods of virus detection, including histopathology, immunohistochemistry, transmission electron microscopy (TEM) and polymerase chain reaction (PCR) against the most important immunogenic genes (TK, gE, gG, ICP4). Compare ILT severity in different locations in Egypt by tracheal histopathological lesion scoring and map the distribution of ILTV in Egypt. The present study was divided into two main studies: - The first part was a surveillance study that conducted on different 42 poultry farms (Sasso, layer and breeders) that showing clinical signs and high mortality rates located across nine governorates in Egypt. The samples were presented to our clinic for examination during the period of 2018 to 2020. Flock history, clinical signs, and gross pathological lesions were recorded in addition to histopathological findings, which complemented the diagnosis during ILTV outbreaks. Examined birds showed respiratory manifestations with expectoration of blood and clotted blood in the tracheal lumen. Histopathological examination of ILT infected birds showed thickening of the mucosa and submucosa of larynx and trachea by vascular changes, inflammatory exudate as well as dense mononuclear cell infiltrates with detached epithelium in the lumen forming syncytial cells contained intranuclear inclusion bodies. In addition, necrosis of epithelial cells, hyperplasia, and desquamation, along with fibrin, free RBCS , cellular debris and heterophils formed a fibrinonecrotic diphtheritic membrane filled their lumens. Sloughed and denuded epithelium were detected in very severe cases.