Verma, P.C.Kamal Deep2017-08-212017-08-212006http://krishikosh.egranth.ac.in/handle/1/5810029176Marek’s disease (MD), which is a lymphoproliferative disease of chickens, remains one of the most important disease. In the present study, occurrence of Marek’s disease virus in ten vaccinated poultry flocks of Haryana (India) from different geographical locations was determined on the basis of clinical signs, gross and histopathology, precipitation test and by polymerase chain reaction (PCR). While all the samples have gross and histopathological lesions suggestive of Marek’s disease i.e. visceral tumors in liver, spleen, kidney and ovary, only five feather follicle tip samples gave a positive precipitation reaction. The feather follicle epithelium of all the samples from ten poultry flocks were positive by polymerase chain reaction. In this assay, primers derived from ICP4 gene of MDV serotype-1 and US3 region in case of HVT were used for amplification. PCR product of four samples on nucleotide sequencing revealed that they were very closely related to virulent Marek’s disease virus and their per cent similarity ranged from 99.2%-100%.enThesis