Infectious Bursal Disease

IBD occurs primarily in chickens. Clinical signs and mortality are generally more severe in birds 3-6 weeks old. However, IBD may occur in chickens as long as they have a functional bursa of Fabricius (1-16weeks of age). Birds infected at less than 3 weeks of age do not have clinical signs. However, destruction of the bursa results in immunosuppression. The younger the bird at the time of infection, the more severe the immunosuppression, resulting in a high degree of susceptibility to subsequent pathogens. Once a premise has been contaminated with IBD virus, the disease tends to recur, usually as a subclinical infection.