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Infectious bursal disease (also known as Gumboro disease) is an immunosuppressive viral disease specific to chickens. In spite of all the information amassed on the antigenic and immunological characteristics of the virus, the disease has not yet been brought fully under control. It is still prevalent in properly vaccinated flocks carrying specific antibodies at levels normally high enough to prevent the disease. Common causes apart, failure of vaccination against infectious bursal disease is associated mainly with early vaccination in flocks of unknown immune status and with the evolution of viruses circulating in the field, leading to antigenic drift and a sharp rise in pathogenicity. Various highly sensitive molecular techniques have clarified the viral determinants of antigenicity and pathogenicity of the infectious bursal disease virus. However, these markers are not universally recognised and tend to be considered as evolutionary markers. Antigenic variants of the infectious bursal disease virus possess modified neutralising epitopes that allow them to evade the action of maternally-derived or vaccine-induced antibodies. Autogenous or multivalent vaccines are required to control antigenic variants in areas where classical and variant virus strains coexist. Pathotypic variants (very virulent viruses) remain antigenically related to classical viruses. The difficulty in controlling pathotypic variants is linked to the difficulty of eliciting an early immune response, because of the risk of the vaccine virus being neutralised by maternal antibodies. Mathematical calculation of the optimal vaccination time and the use of vaccines resistant to maternally-derived antibodies have improved the control of very virulent viruses., (© OIE (World Organisation for Animal Health), 2016.)

The fight against epizootics is today better organized. The tools, methods and strategies used work well and are constantly being improved, which is necessary since disease epidemiology is evolving extremely fast, dominated by a growing complexity associated to global changes and the emergence of new pathologies. The foundation of the strategy is still based on a permanent epidemiological surveillance and the immediate use of appropriate measures. Among the essential prerequisites there is the existence of effective veterinary services, for which support programmes have been developed, notably by the OIE, which is also responsible for the definition of the norms applicable in animal health. Three examples of control programmes against major epidemics are discussed here: Rinderpest (declared eradicated worldwide in 2011), Highly Pathogenic Avian Influenza (H5N1), and Foot and Mouth Disease., (Copyright © 2012 Académie des sciences. Published by Elsevier SAS. All rights reserved.)

Infectious bursal disease (IBD) (Gumboro disease) has been described throughout the world, and the socio-economic significance of the disease is considerable world-wide. Various forms of the disease have been described, but typing remains unclear, since antigenic and pathotypic criteria are used indiscriminately, and the true incidence of different types is difficult to determine. Moreover, the infection, when not fatal, leads to a degree of immunosuppression which is often difficult to measure. Finally, the control measures used are subject to variations, and seldom follow a specific or standardised plan. In the context of expanding international trade, the authors provide an overview of existing knowledge on the subject to enhance available information on the epidemiology of IBD, the identification of reliable viral markers for diagnosis, and the implementation of specific control measures to ensure a global and co-ordinated approach to the disease.