The study was conducted to evaluate in laboratory the immune effects of an isolated precocious Eimeria tenella strain.The chicken were allocated to 5 groups: 4 groups were infected with E.tenella, 1 group was infected without E.tenella as a control.The infection dosages for the 4 infected groups were 2×102,2×103,2×104,2×105ooeysts per chick,respectively.2 weeks after infection,all chicken ere challenged with 2×l0Sthe parental strain oocysts per ehick,a lethal dosage.The result showed the precocious strain had less pathogenicity, and higher immunogenicity.%本试验对选育的柔嫩艾美耳球虫早熟株的免疫效果进行实验室评价。将早熟株分别用2×102个／只，2×103个／只，2×104个／只，2×105个／只的剂量免疫实验动物，免疫2周后，再用亲本株按2×105个／只的致死剂量攻毒，实验结果显示，早熟株致病性较弱且有一定的免疫保护力。
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