The Lethal Effect of Eimeria tenella Extracts on Rabbits

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Abstract
Saline homogenates of material obtained from hemorrhagic ceca of chickens infected with Eimeria tenella yielded a substance that was lethal to rabbits when injected intravenously or intraperitoneally. Partial purification of the toxic substance was effected by precipitation with saturated ammonium sulfate and by adsorption with tricalcium phosphate. Rabbits injected with approximately 0.5 ml of the crude cecal extract or from 5 to 10 mg of either of the partially purified extracts died in 16 to 24 hours. The toxin resembles sarcocystin in its effect on rabbits. Isolated E. tenella oocysts also yielded toxic material upon rupture of the oocyst wall. Toxin-neutralizing antibodies were obtained from rabbits immunized with sublethal injections of toxin. Chickens injected with relatively large amounts of toxin were not adversely affected, did not produce toxin-neutralizing antibodies and were not protected from a subsequent coccidial infection. The relationship between the toxic effects on rabbits and the syndrome of cecal coccidiosis is still obscure.
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