Infectious Bursal Disease Emulsified Vaccine: Effect upon Neutralizing-Antibody Levels in the Dam and Subsequent Protection of the Progeny

Two groups of White Leghorn hens, one vaccinated at 2 weeks against infectious bursal disease (IBD), and the other free of antibodies against IBD virus (IBDV), were vaccinated at 16 weeks old with a suspension or a multiple emulsion of killed IBDV. Untreated hens from each flock were kept as controls. All birds were bled periodically for 50 weeks after vaccination. Twenty-five weeks after vaccination fertile eggs were collected. Antibody levels in the yolk were determined. Chickens hatched from the fertile eggs were bled and challenged with IBDV at weekly intervals to determine the persistence of serum antibodies and resistance to bursal atrophy. Hens revaccinated with the emulsified vaccine and the chickens derived from them had the highest neutralizing and most uniform titers, and complete protection in the chickens lasted to 4 weeks. Two of five chickens were still protected against challenge at five weeks of age. In chickens derived from hens revaccinated with a suspension of killed virus, protection was always partial, being in close relation with age; four of five chicks were protected in the first week of age and the rate of protection diminished to only 1 out of 5 by five weeks of age. Chickens obtained from unrevaccinated hens were protected only during the first week of life.