Organ culture of chicken bursa as a model to study the pathogenicity of infectious bursal disease virus isolates

In vitro study with chicken bursal organ culture was attempted to assess th e pathogenicity of locally isolated infectious bursal disease virus (IBDV) initially isolated from the bursa of naturally infected birds. In bursal or gan culture, lymphoblastic transformation was noticed as early as 24 hr pos tinoculation and reached maximum at 72 hr postinoculation. The other micros copic changes were increased number of macrophages and formation of plasma cells. The IBDV antigen was detected 24 hr onward by coagglutination test w ith antibody coated Staphylococcus aureus strain Cowan I. On the basis of l esion score, the three isolates of IBDV (A, B, and C) were graded as virule nt (B isolate) and moderately virulent (A and C isolates). A similar patter n of pathogenicity was also observed in the in vivo pathogenicity studies i n chicken based on bursa:body weight ratio and histopathologic lesion score . The bursal organ culture thus provides a useful experimental model to dif ferentiate the IBDV isolates on the basis of their virulence.