Characterization of Syrian isolates of Avian Infectious Laryngotracheitis virus by restriction fragment length polymorphism.

Avian Infectious Laryngotracheitis (ILT) has been identified in most countries around the world and remains a threat to the intensive poultry industry (Guy and Bagust, 2003). In this study, polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) of thymidine kinase (TK) gene using restriction endonucleases HaeIII and MspI was utilized to characterize 20 field isolates of ILTV obtained from different chicken flocks during ILT outbreaks in Syria between 2006 and 2009. Combinations of PCR-RFLP patterns classified the ILT virus isolates into three groups. Five isolates were categorized as group I that had identical pattern to the two chicken embryo origin CEO vaccine strains. Nine isolates were categorized as group II that differed in two RFLP patterns from CEO vaccine strains, whereas six isolates categorized as group III that contained a mixture pattern of group I and group II patterns. The results of this study indicated that both wild type and vaccine derived viruses were involved in ILT field cases in Syria.