The gross findings of dehydration, multiple linear hemorrhages within leg muscles and the swollen edematous bursae of Fabricius are typical of IBD infection. The first is subclinical, which causes immunosuppression and is seen in chickens infected prior to 3 weeks of age. Increased incidence of other diseases such as colibacillosis and coccidiosis are seen and result in increased mortality and condemnations at processing. The second is clinical IBD infection. Birds are infected at 3-6 weeks of age and suffer temporary immunosuppression causing increased susceptibility to diseases for a limited period of time.
Vaccination is practiced in order to establish effective immunity.
Case 18-4 . Bursa of Fabricius. There is acute necrosis of the lymphoid follicles with an intact surface epithelium and heterophil exudate in the lumen. Gross lesions observed in the bursa follow a sequence of change over time. Histologic lesions can be found in all lymphoid organs, but are most severe in the cloacal bursa.