Abstract
Chick embryos have been infected with sporozoites of Eimeria tenella, but not with E. brunetti, and died from coccidiosis 5 days after infection.Chick embryos can be protected from death due to coccidiosis by some but not all drugs which give a therapeutic response in chickens. The system is therefore not satisfactory as a screening tool, but may have applications in studies on the nature of drug activity.