Avian infectious laryngo-tracheitis in Egypt. I. Epidemiology, virus isolation and identification.

Serious outbreaks of haemorrhagic tracheitis in poultry induced by infectious laryngo-tracheitis virus (ILTV) have been recorded in Egypt for the first time. The disease occurred in different localities during late 1982 and early 1983. The associated drop in egg production ranged between 5% and 35% and there was a mortality rate which ranged from 0.05% to 19.8%. The causal virus was isolated on the chorioallantoic membrane (CAM) of developing chicken embryos where it induced large yellowish-white pock lesions, 3-4 mm in diameter, by the fifth or sixth day post-inoculation. It was non-lethal to the inoculated embryos. It grew also with cytopathic effect (CPE) on the CER cell line. The CPE was characterized by syncytial formation and intranuclear inclusions. Chickens experimentally inoculated with the virus developed respiratory signs and 14 of 20 birds died with subsequent virus re-isolation. The isolated virus was unable to agglutinate chicken red cells and it was precipitated and partially neutralized by reference serum to ILTV. Viral antigen was detected by the indirect fluorescent antibody technique in tracheal smears obtained from naturally and experimentally infected birds. This is the first report of the isolation of ILTV in Egypt.