Pathogenesis of infectious bursal disease in embryonally bursectomized chickens.

The pathogenesis of infectious bursal disease (IBD) in intact chickens was compared with pathogenesis in chickens that had undergone embryonal bursectomy (EBX chickens), which were challenged at either 2 or 6 weeks of age. All EBX chickens were free of bursa remnants, and those challenged at 6 weeks of age failed to develop primary and secondary antibody responses to sheep red blood cells and bovine serum albumin. A direct fluorescent-antibody technique was used to study the course of infection in the bursa of Fabricius, spleen, thymus, cecal tonsils, and kidneys. EBX delayed but did not prevent the appearance of IBD-infected cells. Virus-positive cells were detected in the thymus of EBX chickens up to 18 days postinfection. Significantly more EBX chickens challenged at 6 weeks of age had hemorrhagic lesion in muscles and intestinal tract than comparable intact chickens had.