Immune Response of White Leghorn Chicks from Vaccination with Different Strains of Infectious Bursal Disease Virus and in the Presence of Maternal Antibodies

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SUMMARY White Leghorn chicks 1 to 11 days old possessing maternal antibodies to infectious bursal disease (IBD) were vaccinated with the 2512-P48, 2512-P84, LKT, and BV strains of IBD virus by different routes. Their dams had been vaccinated against IBD at one day old and revaccinated at 14 weeks and every 90 days thereafter. The 2512-P48, 2512-P84, and LKT strains did not bestow satisfactory immunity on the progeny as measured by challenge and the agar-gel precipitin test. In contrast, the BV strain engendered good immunity when used as a vaccine at as early as 4 days old. Moderate lesions were found histologically in the cloacal bursa in the postvaccination period, although no clinical signs of IBD were noted. Significant immunosuppression did not occur when chicks were vaccinated with BV IBD virus at 4 days old, vaccinated against Newcastle disease 7 days later, and subsequently given Newcastle disease challenge virus. Primary vaccination of White Leghorn chicks to be placed in IBD-endemic areas in the field is discussed with reference to susceptibility to virus infection, vaccination status of the breeders, level of maternal antibodies (7), and the need for using IBD vaccine strains of differing degrees of virulence and immunogenicity to meet frequently varying field conditions.