Comparative Diagnostic Studies on Marek’s Disease in chickens by Use of Histopathology and Molecular Investigation

Hundred-twenty five diseased or freshly dead birds from different domestic poultry flocks chickens flocks layers breeds as (lohman, novagen and native breed as sasso) and sporadic cases were collected and necropsied between the period from Aug. 15, 2012 to Nov. 8, 2014 and samples from each case were collected. The collecting samples were subjected to the pathology and some selected ones (7) for PCR laboratory (stored freezing -20ºC). Liver, spleen, heart, lungs, kidneys, intestine, ovary, proventriculus, gizzard, skin, nerve, bursa of Fabricius, eye and brain were the main examined organs.
Nervous disorders were observed with gasping, diarrhea and emaciation were also visualized besides up to 15% mortalities. Enlargement of sciatic nerves, irregular pupil, grayish-white nodules in the visceral organs and focal discolored areas on the skin were noticed besides ovarian congestion and misshaped ova. Microscopically, heavy pleomorphic cellular infiltrations of small lymphocytes, lymphoblasts, plasma cells and few mesenchymal cells proliferation and heterophil infiltration were seen in all examined organs. Extensive tissue necrosis, congestion, hemorrhage and edema were associated the infiltrations. Six-out of seven were PCR positive for Marek’s disease virus
All investigated birds were regarded as one disease with lesions possessing the same characteristics, but of varying severity (by histopathology). PCR was best tool to detect and confirm the Marek’s disease virus; but consuming time.