Immunization of chickens against coccidiosis with extracts of Eimeria-infected tissues.

Immunization of chickens with extracts prepared from Eimeria-infected tissues was attempted. Significant protection against weight depression was conferred when chickens were inoculated intra-abdominally with tissue extracts prepared from ceca infected with two different strains of E. tenella. When extracts were given intravenously, with or without the adjuvant, polyandenylic-polyuridylic acid, weight depression was not ameliorated after challenge. Experiments using extracts from two strains of E. acervulina- and E. maxima- and one strain of E. brunetti-infected tissues failed to protect against weight gain depression after challenge.