Isolation and Molecular Detection of Marek’s Disease Virus from Layers Chicken Farms in Iraq

Marek’s disease (MDV) is an important oncogenic and immunosuppressive disease of chickens, distributed all over the world affecting mostly all birds at different ages leading to significant economic losses, caused by a Gallid herpesvirus of Alphaherpesvirinae. This study involved the isolation of Marek’s Disease virus-Gallid herpesvirus2 from three clinical specimens (liver, spleen, and feather follicles) collected from layer flocks suspected with MDV for the first time in Iraq. Clinical samples showed hyperplasia, necrosis foci, and hemorrhage on their surface, significant lesions of feather follicle enlargement and detection of tumor masses occasionally. Chicken embryo fibroblast (CEF) cell culture were used for virus isolation, prepared samples were inoculated on CEF for two passages. The main cytopathic effects were cell rounding, cell clusters, Syncytia forming, and plaque formation starting 5 days post-inoculation. The isolates were confirmed by a Taqman real-time PCR technique with a specific primer against viral pp38. Additionally, the pathogenesis of isolates and clinical samples were investigated through molecular technique by detecting Marek's virus genome's tandem 132 repeat region. All tested samples give a single amplification band, indicating that the current circulating strains under investigation are of high virulence. This study will support the need for a better understanding of Marek’s virus disease in Iraqi poultry farms, and enhance its diagnosis to restrict its passive impact on the poultry sector in the country.In summary, this study aimed to isolate Marek’s Disease virus from infected layers’ flocks on cell culture and detect the virulence of these field strains through molecular techniques.