Thesis (M.Sc.) - Cairo University - Faculty of Veterinary Medicine - Department of Clinical Pathology

The present study aimed to differentiate between avian tumor viruses by using the immunohistochemical techniques and histological examination. A total number of 250 samples from 10 different governorates were used, the samples classified as 190 layers, 30 breeders, 20 broilers and 10 turkey. Clinical examination of live bird are carried out, and also necropsy was performed on the dead and sick chickens. Samples were divided into two parts part kept in 10% neutral buffered formalin, and the other frozen for molecular examination. Marek{u2019}s disease (MD) is one of the economically important lymphoproliferative viral disease of poultry causing severe economic loss in the poultry industry. Gross lesions, histopathological examination with histochemical stain and molecular detection by polymerase chain reaction (PCR) were applied to identify the type of lymphoma induced by different tumor viruses. At necropsy, large miliary whitish nodular lesions were seen on the organs with enlargement of sciatic nerve and thickening of feather follicle. Microscopically, lymphoproliferative lesions of various extents were seen in different organs by infiltration of pleomorphic lymphocytes were noted leading to extensive damage of the parenchyma. Lymphoid leukosis showed neoplastic cell populations characterized by large lymphoblastic cells, with poorly defined cytoplasmic membrane and basophilic cytoplasm. While in myeloid leukosis induced by subgroup-J of ALV characterized by infiltration of myelocytic cells which characterized by eccentrically located nuclei and had marked nucleolus with clear mitotic figure. The cytoplasm was filled with conspicuous spherical eosinophilic granules. These myelocytic cells showed characteristic brilliant red colored cytoplasmic granules when stained with May-grünwald Gimsa

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