Abstract
The interference of low or high maternal antibodies titers on the attenuated infectious bursal disease (IBD) virus (IBDV) vaccine infection and its effects on the performance of broilers vaccinated at the 18th day of incubation (in ovo), at one day of age (subcutaneously-SC), or at 15 days of age (drinking water-DW) were investigated. After a series of three live vaccinations, breeders were given or not an IBD oil emulsion vaccine (IBD-OEV) prior to sexual maturity. At day 18 of incubation (in ovo), a commercial vaccine containing HVT and an intermediate IBDV strain or the single HVT vaccine was given. An intermediate IBDV vaccine was given SC at one day of age, or at 15 days of age via DW. The progeny of unvaccinated breeders presented higher neutralizing IBDVspecific antibody (IBDVab) titers at 25 and 40 days of age than those of the progeny of IBD-OEV breeders (p<0.05) at any broilers vaccination age and route. The lower IBDV RNA detection by RT-PCR in the bursa of Fabricius (BF) and the lower IBDV antibody titers in the serum of the groups vaccinated at one and 15 days of age derived from IBD-OEV breeders may indicate antibody-mediated IBDV neutralization. The inovo and one-day vaccinations did not interfere with performance, both in low and high antibody-titered progenies. The in-ovo vaccination against IBD is considered convenient and safe for industrial chickens, irrespective their maternal antibody levels.
Highlights
Infectious bursal disease (IBD) is one the most common diseases of poultry worldwide, and it is an important cause of immunodepression or immunosuppression in chickens
As passive immunity in chickens is mediated by a single antibody class, it may have eventually caused the selection of progressively more virulent IBD virus (IBDV), as occurred in the mid-1980s, a risk which presently challenges the passive protection strategy
At 32 weeks of age, mean IBDV-specific serum neutralizing (SN) titer of breeders vaccinated with the combined oil-emulsion IBDV vaccine at the 18-week of age was much higher than the unvaccinated group (p
Summary
Infectious bursal disease (IBD) is one the most common diseases of poultry worldwide, and it is an important cause of immunodepression or immunosuppression in chickens. As passive immunity in chickens is mediated by a single antibody class, it may have eventually caused the selection of progressively more virulent IBDV, as occurred in the mid-1980s, a risk which presently challenges the passive protection strategy. The challenge is to determine the exact early timeframe of susceptibility for inducing protection with the minimum risk of wild IBDV infection. This problem has been indirectly solved by monitoring breeder flocks for antibody levels and carefully establishing the best date for progeny vaccination with least vaccine
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