Measurement of immunosuppression in chickens caused by infectious bursal disease vaccines using Brucella abortus strain 19.

The serological response of chicks to Brucella abortus strain 19 was monitored over a period of seven weeks to assess the degree of immunosuppression caused by vaccination at one day of age with two infectious bursal disease vaccines. One of the vacy. This vaccine caused severe immunosuppression judged by the minimal serological response following B abortus inoculation. The test also detected a significant delay caused by the other vaccine in the development of the serological response but the maximum titre was not significantly different from that in chicks which had received no infectious bursal disease vaccine.