柔嫩艾美耳球虫早熟系的选育及其生物学特性研究

Eimeria tenella:Selection and Characterization of a Precocious Line

选育制备弱毒疫苗所需的柔嫩艾美耳球虫早熟系并对其生物学特性进行研究。运用Jeffers建立的早熟系选育方法对柔嫩艾美耳球虫山西株（E．tenella SX010323）进行早熟选育，并对其内生发育、致病性、繁殖力、免疫原性、稳定性进行观察和检测。结果表明：经过海兰白雏鸡15次传代之后，E．tenella SX010323潜隐期由141h缩短至120h，卵囊明显缩小。选育得到的柔嫩艾美耳球虫山西株早熟系（E．tenella SX010323P15）其内生发育表现第二代裂殖生殖不完全；亲本株与早熟系对11日龄雏鸡的半数致死量分别为7．52×10^4个／只、27．64×10^4个／只，早熟系在致病性与繁殖力上均较母株大幅度降低，但保留了母株的免疫原性，经早熟系免疫的雏鸡可抵抗亲本株半数致死量的攻击。对选育的早熟系进行放松选择传代10次，其潜隐期、OPG、致病性均保持了早熟系的特征。提示通过早熟选育得到了遗传相对稳定的柔嫩艾美耳球虫早熟系。

In order to select a precocious line of Eimeria tenella with an abbreviated life cycle and characterize its biological attributes for preparation of attenuated vaccine. Precocious Shanxi strain （ E. tenella SX010323） was developed via the method founded by Jeffers, and the corresponding endogenous development stages, pathogenicity, reproductive potential, immunogenicity and stability were observed and detected. The results showed that after 15 generations of passage in Hailanbai chickens prepatent period of E. tenella SX010323 was reduced from 141 hours to 120 hours; the ooeysts were apparently smaller than the parental strain; examination of endogenous development showed that the second generation sehizogony of the selected precocious Shanxi line was incomplete; The LDs0 of 11-day chickens of parental strain and precocious strains were 7.52×10^4 ,27.64×10^4 respectively; the precocious parasite is less pathogenic than the parental strain and has a reduced reproductive potential, but remains the immunogenicity of the parental strain. Hailanbai chickens inoculated with the parasites of the precocious line were well protected against the LD50 challenge of the parental strain. Through a relaxed selection of 10 passages, the precocious line showed genetically stable in its prepatent time, OPG, as well as its pathogenicity. All the above facts revealed that the precocious line of Eimeria tenella with genetical stability was obtained through selection.