Studies on the immunogenicity of seven attenuated lines of Eimeria given as a mixture to chickens.

The ability of attenuated lines of all the seven species of Eimeria which infect the chicken to provide protection against challenge with virulent strains was examined. The parasites were given as a mixture of all seven species to chickens kept on litter in floor pens, by spraying an aqueous suspension of oocysts on to the surface of food in troughs within the floor pens. Treated chickens were challenged 4 weeks later with virulent strains, and changes in weight gain and the presence of gross intestinal lesions were determined. When used in this way, as freshly passaged oocysts or after storage for 3 or 6 months, the consistently good protection afforded by the attenuated lines suggests that they could be applied in the control of coccidiosis in the field.