Vol. 10, Issue 10, Part A (2025)

A total of 155 suspected cases of lymphoproliferative diseases (LPDs) like Marek’s Disease (MD), Lymphoid Leucosis (LL) and Avian Reticuloendotheliosis Virus (REV) from 25 commercial layer chicken farms were studied in and around Namakkal District and Thalaivasal (Salem District). The age groups affected for MD affected was 36 to 45 wks., LL was 46 to 55 wks and REV was 20 wks respectively. The clinical signs of LPDs affected chicken showed lameness, forward and backward paralysis and torticolis. In MD suspected 52 brain and 24 bone marrow cases, each one showed (1/52: 1. 92% and 1/24 : 4.16%) MD positive by histopathological (HP) examination and the lesion score was arrived like score 0-51 cases; score 2-1 case for brain and score 0-23 cases; score 3-1 case for bone marrow respectively. In LL suspected 3 brain and 5 bone marrow cases, brain-1 and bone marrow-3 (1/3: 33. 33% and 3/5 : 60.00%) showed LL positive by HP and the lesion score was score 0-2 cases; score 1-1 case for brain and score 0-2 cases; score 1-2 cases; score 5-1 case for bone marrow respectively. In 1 case of REV suspected brain showed positive by HP and the lesion score was score 1-1. HP lesions of MD affected brain showed focal moderate PLC infiltration was seen in the perivascular area as well as a nodule in the neurophil. In addition, diffuse mild to moderate congestion, focal satellitosis, gliosis, axonal spheroids, perivascular cuffing, perivascular oedema and neuronal vacuolation were also noticed without PLC infiltration and bone marrow showed multifocal moderate PLC infiltration in the haematopoietic tissue. HP lesions of LL affected brain showed focal mild MLC infiltration with lymphoblastic tumour emboli in a blood vessel of the cerebral meninges and bone marrow showed focal mild MLC infiltration in the haemopoietic tissue. HP lesions of REV affected brain showed gliosis with multifocal mild perivascular cuffing with lymphocytes.