ABSTRACT
E. M. Dickinson et al. were the first to vaccinate chickens deliberately against coccidiosis. In-feed vaccination through the use of live encapsulated oocysts is an attractive proposition for the control of coccidiosis. The procedure ensures that numbers of oocysts consumed are directly linked with food intake and that the small but increasing numbers of parasites enhance immunity without causing clinical disease. Control of disease was excellent, particularly in replacement flocks where coccidiosis was frequently diagnosed in contemporaneous flocks of the same age on the same site that were given a diet containing anticoccidial drugs. It is likely that any effective vaccine for coccidiosis used commercially will protect chickens against the pathogenic effects of a coccidial infection but will not necessarily induce an absolute immunity. While vaccines against coccidiosis are likely to become available, it must be realized that none will stimulate the wider effects that are associated with some anticoccidial drugs.
