A sudden onset of mortality in chickens between 2 and 8 weeks of age could indicate an IBDV infection. The presence of distinctive lesions in the bursa of Fabricus and accompanying blood spots in the musculature of the breast and thigh of affected chickens are strong indications.
A significant increase in the IBDV titres 2-3 weeks after a suspected Gumboro infection confirms a diagnosis.
The organ of choice for viral isolation is the Bursa of Fabricus. Bursa collected from affected chickens can be frozen and then dispatched to a suitable laboratory for viral isolation. For viral growth bursa are macerated in an antibiotic treated broth, centrifuged and supernatant fluid inoculated onto the chorioallantoic membrane (CAM) of 9 to 11 day old embryos.