Control of infectious bursal disease in broiler chickens

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Infectious bursal disease (IBD) is an acute and highly contagious infectious disease of immature chickens caused by a virus that belongs to the family Birnaviridae. It is characterized by destruction of lymphocytes in the bursa of Fabricius (BF) which damages the immune system and cause immunosuppression. The disease is a major problem in poultry production areas throughout the world. Because the IBD virus is resistant to many disinfectants and environmental factors, once a poultry house becomes contaminated, the disease tends to recur in subsequent flocks. An effective IBD prevention and control program typically involves a broiler breeder parent vaccination program, an effective barn cleaning and disinfection program, and in many areas, a broiler vaccination program. Immunization of breeders is an important part of the IBD control program. Antibodies produced by the hen are passed through the egg to the broiler chick. These maternal antibodies, if present in adequate levels, can protect young chicks against infection with many field IBDVs. Control of IBD has been complicated by the recognition of "variant" strains of the IBD virus in significant number of broiler barns in Saskatchewan. "Variant" viruses damage BF, even in chicks from well vaccinated hens. "Variant" strains do not cause obvious clinical disease, but can induce severe immunosuppression. Variant IBDVs are not a different serotype of IBD, but they are antigenically different to cause immunosuppresion even in broilers from well vaccinated breeders. IBDV vaccines used in Canada are based on the USA IBDV strains and their effectiveness against Canadian IBDV field strains has not been investigated. Thus, the proposed studies are aimed at to identify proper vaccination programs in broilers and their parent flocks to control IBD and to reduce immunosuppresion and associated secondary diseases. Preventing secondary bacterial diseases associated with immunosuppression will lead to minimize antibiotic use and emergence of antibiotic resistant bacteria.