Vaccination of chicks against infectious bursal disease virus

The effect of different levels of virus neutralizing maternally derived antibodies (MA) on protection against Infectious Bursal Disease Virus (IBDV) was investigated. Broiler chicks originating from three breeder flocks were used. Chicks from the above flocks were challenged at one, two, and four weeks of age. Chicks with no maternal antibodies were not protected. Chicks with medium level antibodies were protected at one and two weeks of age. Chicks with high level maternal antibodies were protected at all the ages tested.; The value of vaccinating chicks with or without MA at hatch with Marek's-IBDV vaccine was investigated. In one experiment, chicks with three levels of maternal antibodies were vaccinated at hatch and challenged at 2 weeks of age. In the second experiment, chicks with high antibody titers were vaccinated and challenged as in experiment one. In the third experiment, chicks from an SPF flock were vaccinated at hatch and 20 days of age and challenged at 2 weeks post primary or secondary vaccination. Only vaccinated challenged chicks from the high titer antibody flock were protected (Exp-1). In chicks with high levels of antibodies (Exp-2), the vaccinated challenged chicks were protected at 5 but not at 10 days post-challenge. SPF chicks receiving either first or second vaccination were not protected (Exp-3).; Candidate IBDV vaccines were examined in SPF chicks at different ages. In one experiment trial 1; three groups of SPF chicks each received one vaccine at hatch. In trial 2, similar groups were vaccinated at hatch and also received another vaccine in drinking water at 31 days of age. Only the variant vaccine conferred complete protection against the challenge virus. However, all the vaccines conferred complete protection in the second trial. In the second experiment three weeks old SPF chicks were vaccinated with the combined standard and variant vaccine. The vaccine conferred complete protection against variant challenge.; It is concluded that vaccination at hatch with live IBDV vaccines may be useful. One vaccine elicited partial protection when given at hatch, however, the same vaccine conferred full protection when given at 3 weeks of age.