Influence of hormonal and chemical bursectomy on the development of acquired immunity to coccidia in broiler chickens.

The effect of bursectomy on the development of acquired immunity to coccidiosis in young broiler chickens was examined. Bursectomy was produced by a combination injection of testosterone at 12 days of embryonation and cyclophosphamide at 1 and 2 days after hatching. Immunity to coccidiosis developed in bursectomized chickens immunized with commercially prepared vaccine (CocciVac D) as were measured by resistance to challenge infection at either 6 or 10 weeks of age. Bursectomy had no marked effect on the development of cell-mediated immunity as measured by delayed type hypersensitivity to coccidial oocyst. Since the cell-mediated immune response was not inhibited in the bursectomized chickens, this response was necessary for the development of acquired immunity to coccidiosis.