Abstract: High levels of immunity are achieved in chickens inoculated intramuscularly or orally with E. acervulina extract immunogens. These extracts contain at least 20 polypeptides which induce a protective immune response not only against E. acervulina but also against E. tenella and E. maxima. The resulting immunity prevents intestinal lesions and reduces the number of viable oocysts in vaccinated and challenged birds. One or more of these polypeptides can be used as an immunogen to protect against coccidiosis.

Abstract: Sporozoites of coccidia fail to develop in chickens which are immune and many are blocked from penetrating host cells. Although previous attempts to immunize chickens with non-viable coccidial antigens have been unsuccessful it has been discovered that extracts from sporozoites or sporulated oocysts of E. tennella induce high levels of protective immunity. These extracts contain at least 15 polypeptides many of which are associated with the surface of the sporozoite and induce good immune responses. Antibody to these polypeptides blocks sporozoite-host cell penetration in vitro and neutralizes sporozoites in vivo. One or more of these polypeptides may be used as an antigen to protect against coccidiosis.