| dc.description.abstract | The current study was conducted to evaluate the pathogenicity and pathology of infectious bursal
disease virus in commercial broiler chickens. A total of 45 bursa of Fabricius were collected from 9
commercial farm of different age (18-29 days) of different areas at Sylhet region. During necropsy
both chickens and Bursa of Fabricius (BF) were weighed and examined for gross lesion and processed
for histological investigations. Bursal Index and bursal lesion scoring were made to evaluate
pathogenicity of the virus. The results showed that the weight of bursa increased effectively according
to the body weight. According to the evaluation system 44.44% belongs to the bad category, 22.22%
medium, 11.11% average and 22.22% excellent category. In post mortem examination there was
severe hemorrhage present on BF, breast and thigh muscle. Hemorrhage was found at the junction
between proventriculus and gizzard. Gelatinous and atrophied bursa was also found. Bursal lesion
scoring was done based on histopathological investigations, the highest bursal lesion score was 4.6
±0.40 that indicates bursal atrophy caused by very virulent strain. Bursa were characterized by
atrophy, necrosis, fibroplasia, lymphoid depletion, cyst formation and infiltration of inflammatory
cells. According to Bursal Index and the observed lesions of BF the virus causing infection of very
virulent type. In conclusion, based on the results of the study most of the IBDV infected farms were
affected with vvIBDV. However, virus isolation and determination of pathogenicity at laboratory are
recommended. | en_US |
