柔嫩艾美耳球虫早熟株免疫剂量研究

CHARACTERIZATION OF A PRECOCIOUS LINE OF EIMERIA TENELLA

为了确定柔嫩艾美耳球虫（Eimenatenella）早熟株合适的免疫剂量，本文设立7个早熟株免疫攻虫组、1个不免疫攻虫组和1个不免疫不攻虫组，免疫组的免疫剂量为孢子化卵囊100、200、400、600、800、1000和2000个／羽，经嗉囊感染，7日龄首次免疫，14日龄以同等剂量进行第二次免疫，21日龄以8×10^4个／羽的同源母株进行攻虫，28日龄结束试验，以存活率、增重、肠道病变记分、血便数量、卵囊减少率为观测指标。对免疫保护效果较好的3个免疫剂量进行重复试验，同时设置商品化球虫疫苗对照组，免疫方法、试验周期、试验指标同第一批试验。结果显示：攻虫后，不免疫攻虫组出现5％死亡，而各免疫组来出现死亡；各免疫组卵囊减少率在61．57％～69．52％；200～2000免疫组的增重与不免疫不攻虫组差异不具备显著统计学意义（P〉0．05）；600～2000免疫组的肠道病变记分和血便数量均明显少于不免疫攻虫组（P〈0．05）。用600、800和1000进行重复试验，三个免疫组攻虫期间均来出现死亡，而不免疫组和疫苗对照组均出现5％死亡；三个免疫组的增重均明显高于不免疫攻虫组和疫苗对照组（P〈0．05）；早熟株免疫组的肠道病变记分和血便数量明显低于不免疫攻虫组（P〈0．05），而疫苗对照组与不免疫攻虫组的相当（P〉0．05）；卵囊减少率在66.30％-78．75％，高于疫苗对照组的51．82％。结果表明，该柔嫩艾美耳球虫早熟株保持了良好的免疫原性，不同免疫剂量均能诱发鸡产生免疫保护力，其中600、800和1000个／羽的免疫效果均优于疫苗对照组，可考虑以600个／羽作为该早熟株在疫苗制备中的推荐免疫剂量。

In the present study, a precocious line of Eimeria tenella was evaluated for its efficacy to protect chickens from virulent challenge. The first trial included 7 immunization-challenge groups, one nonimmunization-challenge group and one nonimmunization- nonchallenge group. Immunization doses at 100, 200, 400, 600, 800, 1000 and 2000 sporulated oocysts of the precocious line were orally administered twice to chickens at 7 and 14 days old. Chickens were challenged at 21 days old with 8× 10^4 sporulated oocysts of the parent strain and terminated at 28 days old. Survival rates, weight gains, intestinal lesion scores, fecal scores and oocyst inhibitionratios were recorded. No death occurred in all immunization-challenge groups while chickens in nonimmunization-challenge group showed 5% mortality. The reduction of oocyst ratios in immunization-challenge groups ranged from 61.57% to 69.52%. The weight gains of immunization-challenge groups with 200-2000 sporulated oocysts were similar to that of nonimmunization-nonchallenge （P〉0.05）. The intestinal lesion and fecal scores of immunization-challenge groups with 600-2000 sporulated oocysts were significantly lower than that of nonimmunization-challenge group （P 〈 0.05）. Subsequently, three immunization doses at 600, 800 and 1000 sporulated oocysts were repeated following the same protocol used in the first trial and a commercial coccidiosis vaccine was also included. All chickens in immunization-challenge groups were healthy but chickens in nonimmunization-challenge group and vaccine group showed 5% mortality. The weight gains of three immunization-challenge groups were significantly higher than those of nonimmunization-challenge and vaccine groups （P 〈 0.05）. The intestinal lesion and fecal scores of three immunization-challenge groups were significantly lower than that of nonimmunization-challenge group （P 〈 0.05）, but the difference was not significant （P〉 0.05） with vaccine group. The reduction of oocyst ratios （66.30%-78.75%） of three immunization-challenge groups was higher than that of vaccine group （51.82%）. Results demonstrated that the precocious line orE. tenella maintained good immunogenicity and induced sufficient protection at doses of 600, 800 and 1000 sporulated oocysts. Therefore, the immunization dose at 600 sporulated ooeysts was recommended for use in the development of an attenuated live coccidiosis vaccine.