Effective immune-prophylactics against infectious Bursal disease (disease Gumboro) the most important precondition for keeping healthy chickens and profitable production of poultry meat and eggs

When in 1962 in the Avian Disease journal was published a COSGROVE article about a new disease, observed for the first time in 1957/1958 in broiler chickens at a poultry farm near the town of Gumboro, State of Delaware (USA), hardly no one knew the importance of this nosological unit. At that time, a little is known about Fabricii bag (Bursa Fabricii) of the birds and its key role in relation to immune processes and mechanisms of formation of antibodies. Today it is known that the bursa is the target organ for virus strains of Infectious bursal disease (IBD) and their replication in the lymphoid follicles leading to their destruction and by thus interrupting the synthesis of antibodies in B-lymphocytes, which are responsible for humoral immunity and immunosuppression. A fully functioning immune mechanism is of great importance not only for the organism, which must be able to produce antibodies against the field and vaccine viral and bacterial strains to protected against infections and moreover, it is a prerequisite for the provision of so called maternal immunity. This immunity is transmission of yolk antibodies, which pass through the final stage of fetal development and by the complete absorption of the yolk bag during the first 7-10 days after hatching, in the blood of chicks and protect them against clinical manifestation of the infectious agents. For that reason chicks are protected against Infectious bursal disease, which thus passes inapparent. Absence or insufficient maternal immunity leads to significant morbidity and mortality in 2 to 10 weeks aged birds. These circumstances impose the development of effective vaccines against IBD using field strains isolated from dead chickens and attenuated through passages in chick embryos and/or cell cultures. Such vaccines have been established in Bulgaria (Luepke et al., 1984) against classical IBD-virus, and later against highly virulent IBD-virus (Luepke et al., 1992).BG; bg; EFSAfocalpoint@mzh.government.b