STUDIES ON PREVALENCE, PATHOLOGY AND MOLECULAR DIAGNOSIS OF INFECTIOUS BURSAL DISEASE IN BROILERS

STUDIES ON PREVALENCE, PATHOLOGY AND MOLECULAR DIAGNOSIS OF INFECTIOUS BURSAL DISEASE IN BROILERS Infectious bursal disease (IBD) is a highly contagious disease of young chickens caused by infectious bursal disease virus (IBDV), characterized by immunosuppression and mortality generally at 3-6 weeks of age. It has contributed significantly in overall losses to poultry industry because of increased mortality due to IBD and other diseases occurring as a result of vaccination failures due to immunosuppressive effect of the disease. The present study was undertaken to study prevalence, pathology and molecular diagnosis of IBD in broilers. Prevalence of IBD was found to be much higher in Durg (12%) district compared to Rajnandgaon (10%) and Raipur (8%) in the age group of 3 to 6 weeks. Most of the birds suspected to have died of IBD showed petechial and ecchymotic haemorrhages in the leg and breast muscles, haemorrhages at the junction between gizzard and proventriculus, congestion and haemorrhages on the serosal and mucosal surfaces of the bursa, swollen and mottled or severely atrophied spleen and swelling and paleness of kidney. Histopathologically, severe depletion of lymphocytes in the bursa of Fabricius, spleen and thymus were observed. Degenerative and necrotic changes along with haemorrhage in the kidney and necrosis of hepatocytes in the liver were observed in the IBD infected birds. Organ weight factor of bursa of Fabricius and spleen were calculated and found significant (P<0.01) decrease in weight of bursa of Fabricius and spleen of IBD affected birds compared to the normal birds. Ten blood samples from Durg, Rajnandgaon and Raipur district were collected and compared with ten blood samples from normal healthy birds. There were significant increase in haemoglobin (g/dl), packed cell volume (%), total leukocyte count and heterophil (%) and significant decrease in lymphocyte (%) and eosinophil (%) in the IBD infected birds compared to healthy birds. Serum samples were collected from the IBD affected flock for ELISA test. The ELISA test revealed antibody titer which ranged from 3689 -7974 (mean titer 5602 ± 567.86), 4976 7393(mean titer 6243 ± 348.36) and 4990 – 6516 (mean titer 5522 ± 343.00) in affected broilers of Durg, Raipur and Rajnandgaon district respectively. The bursae of Fabricius and spleens of broilers of Durg, Rajnandgaon and Raipur showing lesions suggestive of IBD were collected for RT-PCR. A total of 53 samples were taken for the detection of IBDV by using IBDV specific primers. Out of 53 IBD affected samples of bursa and spleen 45 samples produced an amplicon of 643bp indicating positive result (84.9%) for IBDV. Thus in the present study RT-PCR was found to be highly sensitive test for the diagnosis of IBDV in field conditions. Dr. R. C. Ghosh Major Advisor Fig. 1: Effect of IBD on organ weight factor of liver and kidney in broilers Fig. 2: Photograph of IBD infected bird showing petechial and ecchymotic haemorrhages in the leg Fig. 3: Photograph of IBD infected bird showing petechial and ecchymotic haemorrhages in the thigh muscle Fig.4: Photograph of IBD infected bird showing swelling of bursa of Fabricius Fig.5: Photograph of IBD infected bird showing congestion and haemorrhages on the serosal and mucosal surfaces of bursa of Fabricius Fig.6: Photograph of IBD infected bird showing cheesy mass in the lumen of bursa of Fabricius Fig.7: Photograph of IBD infected bird showing swollen and mottled appearance of spleen Fig.8: Photograph of IBD infected bird showing atrophied spleen (a) and normal spleen (b) Fig.9: Photograph of IBD infected bird showing swollen and pale kidneys Fig.10: Photograph of IBD infected bird showing haemorrhages at the junction between proventriculus and gizzard Fig.11: Section of bursa of Fabricius of IBD infected bird showing severe depletion of lymphocytes and necrosis (H & E X 100) Fig.12: Fig.11 in high power (H & E X 400) Fig.13: Section of bursa of Fabricius of IBD infected bird showing area of lymphoid depletion along with serous exudation (H & E X 400) Fig.14: Section of spleen of IBD infected bird showing lymphoid depletion of various degrees (H & E X 400) Fig.15: Section of kidney of IBD infected bird showing haemorrhage in the interlobular capillaries (H & E X 400) Fig.16: Section of kidney of IBD infected bird showing degenerative and necrotic changes of proximal and distal convoluted tubules (H & E X 400) Fig. 17: Section of kidney of IBD infected bird showing degenerative and necrotic changes of proximal and distal convoluted tubules leading to atrophy of glomerulus (H & E X 400) Fig. 18: Section of lung of IBD infected bird showing severe pneumonic changes like thickening of interlobular septa due to heavy infiltration with mononuclear cells (H & E X 400) Fig. 19: Section of lung of IBD infected bird showing severe congestion leading to stage of grey hepatization (H & E X 400) Fig. 20: Section of lung of IBD infected bird showing serofibrinous exudation in the bronchiole (H & E X 400) Fig. 21: Section of brain of IBD infected bird showing congestion (H & E X 400) Fig. 22: Section of brain of IBD infected bird showing oedematous changes (H & E X 400) Fig. 23: Section of liver of IBD infected bird showing severe haemorrhage (H & E × 400) Fig. 24: Section of liver of IBD infected bird showing haemorrhage and severe necrosis of hepatocytes (H & E × 400) Fig. 25: Section of thymus of IBD infected bird showing severe medullary lymphocytic depletion (H & E × 100) Fig. 26: Fig. 25 in high power (H & E × 400) Fig. 27: Section of thymus of IBD infected bird showing severe medullary lymphocytic depletion along with haemorrhage and congetion (H & E × 400) Fig. 28: Effect of IBD infection on mean hemoglobin values (g/dl) in broilers Fig. 29: Effect of IBD infection on mean PCV values (%) in broilers Fig. 30: Effect of IBD infection on mean TEC values (millions/cu.mm) in broilers Fig. 31: Effect of IBD infection on mean TLC values (thousand/cu.mm) in broilers Fig. 32: Effect of IBD infection on mean heterophil values (%) in broilers Fig. 33: Effect of IBD infection on mean lymphocyte values (%) in broilers Fig. 34: Effect of IBD infection on mean eosinophil values (%) in broilers Fig. 35: Effect of IBD infection on mean basophil values (%) in broilers Fig. 36: Effect of IBD infection on mean monocytes values (%) in broilers Fig. 37: ELISA test showing positive result by detecting IBD antibody Fig. 38: Gel electrophoresis of PCR amplified product (643bp) of IBD virus from suspected bursa and spleen sample