International Journal of Livestock Research eISSN : 2277-1964 NAAS Score -5.36 Vol 9 (8) Aug ’19 Hosted@www.ijlr.org DOI 10.5455/ijlr.20190405084024 Page140 Original Research Lymphoid Leucosis and Marek’s Disease in Chicken – Gross and Histopathological Studies Y. Ravikumar * , B. Ashok Kumar Reddy, M. Lakshmi Namratha, G. Ramesh, B. Mahesh and M. Lakshman Department of Veterinary Pathology, PVNRTVU, Hyderabad-500030, INDIA *Corresponding author: ravikumaryadala@gmail.com Rec. Date: Apr 05, 2019 20:40 Accept Date: Jul 08, 2019 10:53 DOI 10.5455/ijlr.20190405084024 Abstract Study of occurrence of Lymphoid leucosis (LL) and Marek’s disease (MD) in chicken was taken up in Department of Veterinary Pathology, College of Veterinary Science Rajendranagar, Hyderabad. 2,157 birds were presented to post-mortem examination to the department; out of 2157 carcasses, 393 (18.22%) cases showed the lesions of neoplastic conditions; Out of these positive cases, 281 (13.08%) were diagnosed as MD and remaining 112 (5.20%) were LL. These conditions were diagnosed based on gross and histopathological changes. Grossly, diffused enlargement of liver, kidneys and spleen with white foci were noticed in LL; there was enlargement of liver, kidney, spleen, proventriculus and thickening of nerves in MD. Microscopically, diffuse proliferation and infiltration with uniform neoplastic lymphoblast cells were noticed in various visceral organs in LL and pleomorphic in MD. Key words: Chicken, Gross, Histopathological Studies, Lymphoid Leucosis, Marek’s Disease How to cite: Ravikumar, Y., Reddy, B., Namratha, M., Ramesh, G., Mahesh, B., & Lakshman, M. (2019). Lymphoid Leucosis and Marek's Disease in Chicken - Gross and Histopathological Studies. International Journal of Livestock Research, 9(8), 140-144. doi: 10.5455/ijlr.20190405084024 Introduction Avian leucosis is a group of diseases of chicken comprises of lymphoid, erythroid, myeloid leucosis, Other tumours such as fibroma, haemangioma, nephroblastoma and Osteopetrosis. Avian leucosis is prevalent throughout the world. Lymphoid leucosis is the commonest neoplastic condition in chicken caused by avian leucosis virus (ALV) usually occurs between 14th to 30th week of age. Incidence is highest at about sexual maturity (Vegad and Katiyar, 2001) which induces lymphoma in chicken called Lymphoid leucosis (LL) (Pizer and Humpheries, 1989). Marek’s disease (MD) is a lymphoproliferative disease of chicken caused by MD herpes virus (MDV) and is characterized by lymphoma formation in visceral organs, muscles, skin and lesions in peripheral nerves (Calnek and Witter, 1991). These two avian neoplastic diseases are responsible for economic loss due to both mortality and depressed performance (Panda, 1983). Hence, the