PATHOMORPHOLOGICAL AND MOLECULAR DIAGNOSIS OF INFECTIOUS BURSAL DISEASE
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Date
2020-12
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College of Veterinary Science, Assam Agricultural University, Khanapara, Guwahati
Abstract
The present investigation was carried out to know the pathomorphology of
Infectious Bursal Disease in different organized and un-organized poultry farms in and
around the Guwahati city, Kamrup district, Assam.
Altogether 1650 birds were necropsied, out of which 1279 birds from 29 different
outbreaks were diagnosed as suspected of IBD based on gross lesions observed.
Clinical signs commonly recorded were vent pecking, dullness, depression,
anorexia, ruffled feathers and yellowish white diarrhea.
In gross pathological study, bursa of Fabricius were found to be invariably
affected with lesions like swelling, edema and hemorrhage. Few bursa of Fabricius
showed atrophy. Moderate to severe haemorrhages in the breast and thigh muscle were
consistently observed. The kidneys were enlarged and mottle with whitish pale colour
appearance. Hemorrhagic lesions were also noticed in extra bursal lymphoid organs like
spleen, thymus and caecal tonsils.
Histopathologically, there were mild to severe depletion of lymphocytes in the
bursa of Fabricius, spleen, thymus and caecal tonsils. Heterophilic infiltrations were also
consistently observed in these organs. Complete depletion of lymphocytes with
formation of cystic cavity were noticed in some bursal follicle. Marked thickening of the
inter-follicular space with proliferated fibrous connective tissue were another
characteristic bursal lesion observed. Muscle sections revealed haemorrhages and
necrosis. Kidney showed degenerative changes and necrosis in proximal and distal
convoluted tubules. There were glomerular shrinkage in few cases. Degenerative changes
of the hepatocytes were the commonly observed histopathological changes in liver.
In scanning electron microscopic study of bursa of Fabricius, moderate to severe
erosion and ulceration of mucosal plica and exposure of reticular fibers were noticed
after exuviations of epithelial and other cells were noticed. Button like depressed
structures were seen in follicles and some follicles appeared as empty craters due to
complete lymphocytic depletion. Spleen and thymus also showed moderate to severe
lymphocyte depletion characterized by presence of homogenous mass.
In transmission electron microscopic, spherical virus particle without a clear
membrane were observed in the cellular debris of the cytoplasm of the follicular cells.
Mitochondrial changes like crystolysis were also recorded.
ABSTRACT
The disease was confirmed by detection of viral antigen and viral nucleic acid in
165 representative samples by Indirect IPT and 612 representative samples by RT-PCR.