Marek's disease virus in Egypt: historical overview and current research based on the major mdv-encoded oncogene meq

An update survey of the MDV strains circulating in the Egyptian poultry flocks during 2015 -2016 was conducted. Twenty one vaccinated chicken flocks suffering from different form of lymphomas, representing different governorates in the Egyptian Delta, were screened for MDV infection. Pathological findings in the visceral tumours and presence of viral DNAs with variable mitotic figures were observed in the examined visceral organs. Eight samples were screened positive for the major MDV-encoded oncogene Meq which was subjected for alignment and phylogenetic analysis. The eight studied consensus amino acid sequences of Meq proteins possess several amino acid mutations associated with the MDV virulence and a unique distortion in the Proline repeats (Proline-to-Alanine) at position 176 in the Egyptian MDV strains. The Phylogenetic analysis grouped the eight analysed sequences with the previously investigated Meq from Egypt (2011-2013) together with the very virulent European and Chinese MDV isolates. The latter confirmed the geographical structuring of the Egyptian MDV strains together with the Eurasian origin viruses in an independent taxonomic unit distant from the North American strain.