author(s)
R Bharathi, K Karthik, N Pazhanivel, S Hemalatha, K Shoba, Parimal Roy and G Dhinakar Raj

abstract
A retrospective study on histopathological analysis and bursal lesion scoring of Infectious bursal disease (Gumboro disease) was conducted at Central University Laboratory, TANUVAS, Chennai for the period of 34 months from October 2015 to July 2018. In this study, the samples were received from various parts of Tamil Nadu for histopathological examination. A prevalence of 11.36% (119 cases) was recorded out of 1047 poultry cases. The prevalence of IBD is influenced by age of birds with an increase in the likelihood of IBD occurring within the age range of 4-7 weeks. Based on the history received, most of the affected chicken were anorectic, reluctant to move and showed ruffled feathers with watery diarrhoea and severe prostration. The gross lesions like muscle haemorrhages, haemorrhages in the proventricular gizzard junction and enlargement of the bursa of Fabricius were observed. On histopathological examination, 119 cases showed lesions in the bursa, the lesion scores varying from 1 to 5. Out of 119 cases, six samples had a bursal score of 1, thirty-nine samples had a bursal score of 2, fifty samples had a bursal score of 3, twenty-three samples had a bursal score of 4 and one sample had a bursal score of 5. In this study, most of the affected cases belongs to score 2-4, which caused mortality in affected birds. Among them, the birds with lesion score 3 had a higher mortality rate. This study recommends that poultry farmers should be encouraged to improve farm biosecurity and ensure that their birds are vaccinated.