Molecular characterization and phylogenetic analysis of Marek's disease virus in chickens from Ogun State, Nigeria.

Marek's disease (MD) is caused by oncogenic MD virus serotype 1 (MDV1) and is characterized by lymphoproliferative lesions resulting in high morbidity and mortality in chickens. Despite being ubiquitous on poultry farms, there is a dearth of information on its molecular characteristics in Nigeria. This study aimed at characterizing three virulence genes ( and ) of MDV1 from chickens in Ogun state, Nigeria. Blood, feather quill, and tumour samples of chickens from different commercial poultry farms in Ogun State were pooled, spotted on 107 FTA cards, and screened for MDV1 by polymerase chain reaction (PCR). Phylogenetic analysis was carried out to compare Nigerian MDV1 , and genes sequences with the published references. Thirteen samples were MDV1-positive and the , as well as and genes from the different samples were 100% identical. The genes contained 339 amino acids (aa) with three PPPP motifs in the transactivation domain and two interruptions of the PPPP motifs due to proline-to-arginine substitutions at positions 176 and 217 resulting in a 20.88% proline composition. Phylogenetic analysis revealed that the gene clustered with strains from Egypt and very virulent ATE2539 strain from Hungary. Mutations were observed in the pp38 protein (at positions 107 and 109) and protein (at positions 4 and 31). Based on the molecular analysis of the three genes, the results indicate the presence of MDV1 with virulence signatures; therefore, further studies on pathotyping of Nigerian MDV1 from all states should be performed. genes were 100% identical between Nigerian MDV strains.Proline content in Nigerian gene was 20.88% with two PPPP motifs interruptions. genes of Nigerian MDV were similar to Egyptian and Indian strains.