The immunodepressive effect of infectious bursal agent on vaccination against Newcastle disease

Immunodepression due to an infectious bursal agent (IBA) infection depends on the age of the birds, the time of Newcastle disease (ND) vaccination and the IBA strain used. The immunodepressive effect of IBA on ND vaccination can be avoided by vaccinating the chicks against ND at day old or by using attenuated strains of IBA in all commercial vaccines.