A cDNA clone derived from sporulated oocysts of Eimeria tenella and encoding the expression product GX3262 was identified using a monoclonal antibody raised against Eimeria acervulina sporozoites. After challenge with an experimental E. tenella infection, the greatest degree of protection in immunized broiler chickens was seen after only a single immunization of 2-day-old birds with a live recombinant E. coli preparation (Miller et al., 1989).