Molecular and Immunopathological Investigations of Marek’s Disease in HVT Vaccinated Chicken Flocks

Abstract

Background: The present investigation was carried out on poultry carcasses brought to the Department of Veterinary Pathology, LUVAS, Hisar from Herpesvirus of turkeys (HVT) vaccinated chicken flocks and suspected for viral neoplastic conditions on the basis of necropsy. Conventional and molecular techniques for the confirmation of the Marek’s disease (MD) were studied. For differential diagnosis from other oncogenic viral infections immunohistochemistry as an important tool was investigated. Methods: The conventional diagnosis of MD) was done on basis of clinical signs, gross lesions and histopathology of proliferate lesions; as lymphomatous lesions consist of pleomorphic lymphocytes. For confirmatory diagnosis molecular techniques were employed to detect MD virus specific Meq gene by Taqman probe real time PCR and nested PCR. For differential diagnosis of mixed oncogenic viral infections, immunohistochemistry (IHC) using B and T cell differentiation markers (CD79 alpha and CD3) was employed. Result: Specific Meq gene by Taqman probe real time PCR was positive in 92.5% suspected cases; while nested PCR technique gave positivity in 55% cases. The immunohistochemical reactivity for CD3 gave positive reactivity in the cytoplasm and cell membrane and negative reaction for CD79 alpha in MD positive cases, while in cases with mixed infections of MDV and other viral neoplastic conditions, cells showed positive reactivity to both CD3 and CD79 alpha in neoplastic proliferates.