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Infectious bursal disease (IBD), also known as Gumboro disease, is an immunosuppressive disease that leads to economic losses associated with:
Because of the immune suppression, birds that survive are at risk for secondary infections from opportunist pathogens.
The cause of IBD, infectious bursal disease virus (IBDV), is very difficult to remove from a poultry house once it has become established. Thus, the control of IBD is primarily through vaccination.
Shortly after it was discovered, IBDV vaccines were developed and provided excellent protection against the virus. Over the next 60 years, selection pressures have contributed to the evolution of IBDV so that commercial vaccines no longer provide complete protection against the numerous antigenic strains currently infecting poultry flocks.
The solution to this problem could be via a new vaccination technology using VLP (virus-like particle vaccines).
Vaccination strategies against IBD.
The first line of defence against this disease should be biosecurity, but as mentioned above, the virus is very difficult to inactivate and remove from houses.
Therefore, the second line of defence to protect chicks against infection is through the use of vaccines that are used both in the breeder flocks and in the chicks.
The first approach to protect against IBD is to produce maternal immunity in young chicks by vaccinating the breeder flock. Antibodies to IBDV will then be transferred to the chicks through the yolk.
Since IBDV infects immature B-cells, it is critically important to protect young chicks from infection as soon as they are placed on the farm.
Typically breeder birds are primed with live-attenuated IBDV vaccines when they are young and then given a killed IBDV vaccine around 18 weeks of age when they are moved into the layer house.
Vaccination of young chicks
Maternal immunity to IBDV should last about 3-4 weeks at which time the birds will become susceptible to a field virus infection. To protect against IBDV infections beyond what maternal immunity can provide, an active immunity in the chicks is needed. This has been accomplished using live-attenuated IBDV vaccines. The timing of vaccination with these live vaccines is critical because maternal immunity can interfere with their ability to stimulate the immune system of young chicks.
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