巨型艾美耳球虫早熟株免疫剂量研究

摘要

为了确定巨型艾美耳球虫（Eimeriamaxima）早熟株合适的免疫剂量，本文设立7个早熟株免疫攻虫组、7个母株免疫攻虫组、1个不免疫攻虫组和1个不免疫不攻虫组，7个早熟株/母株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8×104个/羽的同源母株进行攻虫，28日龄结束试验，以增重、肠道病变记分和卵囊减少率为试验指标。对早熟株中免疫保护效果较好的2个免疫剂量进行重复试验，免疫方法、试验周期、试验指标和攻虫剂量同第一批试验。结果显示：早熟株和母株200、400、600、800、1000、2000个/羽免疫组攻虫后的增重与健康对照组差异不显著（P>0.05），100个/羽免疫组明显低于健康对照组（P<0.05）；各免疫组的卵囊减少率均达90%以上，肠道病变记分均与不免疫攻虫组差异不显著（P>0.05）。用早熟株200、400个/羽进行免疫重复试验，两个免疫组攻虫期间的增重和肠道病变记分均与健康对照组差异不显著（P>0.05），而与不免疫攻虫组差异显著（P<0.05），其卵囊减少率均在86%以上。研究结果表明，该巨型艾美耳球虫早熟株保持了良好的免疫原性，每只鸡免疫200或400个孢子化卵囊均可诱发鸡产生良好的免疫保护力，可考虑以200个孢子化卵囊作为该早熟株在疫苗制备中的推荐免疫剂量。%In order to determine optimal immunization dose of a precocious line of Eimeria maxima, the first trial was conducted including 7 groups immunized with a precocious line, 7 groups immunized with its parent strain, 1 unimmunized-challenged group and 1 unimmunized-unchallenged group. Dosages of 100, 200, 400, 600, 800, 1000 and 2000 sporulated oocysts of the precocious line or its parent strain were administered orally to 7-day-old chickens for twice at a 7-day interval. Seven days later, all chickens in the challenged grorps were challenged with 8×104 sporulated oocysts of the parent strain. Weight gains, intestinal lesion scores and reduction of oocyst ratios were used to evaluate the efficacy. Weight gains of immunization groups with 200-2000 sporulated oocysts of the precocious line and parent strain had no significant difference from those of unimmunized-unchallenged group (P>0.05) while weigh gains of immunization groups with 100 sporulated oocysts were significantly lower than those of unimmunized-unchallenged group (P<0.05). Oocyst production were reduced over 90%in all immunization groups. Intestinal lesion scores of all immunization groups were similar to those of unimmunized-challenged group (P>0.05). The effectiveness of doses of 200 and 400 sporulated oocysts of precocious line were repeated. Both weight gains and intestinal lesion scores of these two immunization groups were similar to those of unimmunized-unchallenged group (P>0.05), but significantly different from those of unimmunized-challenged group (P<0.05). Reduction of oocysts ratios was over 86%. Results from both trials demonstrated that the precocious line of E. maxima maintains good immunogenicity and could induce sufficient immunological protection at 200/400 immunizing dosage. Therefore, 200 sporulated oocysts were determined to be optimal immunization dose.