Eimeria species parasites infect the gastrointestinal tract of chickens, causing disease and impacting on production. The poultry industry relies on anticoccidial drugs and live vaccines to control Eimeria and there is a need for novel, scalable alternatives. Understanding the outcomes of experimental infection in commercial chickens is valuable for assessment of novel interventions. We examined the impact of different infectious doses of Eimeria tenella (one low dose, three high doses) in three commercial layer chicken lines, evaluating lesion score, parasite replication and cytokine response in the caeca. Groups of eight to ten chickens were housed together and infected with 250, 4,000, 8,000 or 12,000 sporulated oocysts at 21 days of age. Five days post-infection caeca were assessed for lesions and to quantify parasite replication by qPCR and cytokine transcription by RT-qPCR. Comparison of the three high doses revealed no significant variation between them in observed lesions or parasite replication with all being significantly higher than the low dose infection. Transcription of IFN-γ and IL-10 increased in all infected chickens relative to unchallenged controls, with no significant differences associated with dose magnitude (p > 0.05). No significant differences were detected in lesion score, parasite replication or caecal cytokine expression between the three lines of chickens. We therefore propose 4,000 E. tenella oocysts is a sufficient dose to reliably induce lesions in commercial layer chickens, and that estimates of parasite replication can be derived by qPCR from these same birds. However, more accurate quantification of Eimeria replication requires a separate low dose challenge group. Optimisation of challenge dose in an appropriate chicken line is essential to maximize the value of in vivo efficacy studies. For coccidiosis, this approach can reduce the numbers of chickens required for statistically significant studies and reduce experimental severity.

艾美球虫种寄生虫感染鸡的胃肠道，引起疾病并影响生产。家禽业依靠抗球虫药和活疫苗来控制艾美球虫并且需要新颖，可扩展的替代方案。了解商业鸡实验性感染的结果对于评估新的干预措施很有价值。我们检查了不同感染剂量的艾美球虫（三个低剂量，三个低剂量）在三个商业鸡群中进行评估，评估盲肠的病变评分，寄生虫复制和细胞因子反应。将八到十只鸡的组放在一起，并在21日龄时感染250、4,000、8,000或12,000个带孢子的卵囊。感染后五天，评估盲肠的病变并通过qPCR定量寄生虫复制，并通过RT-qPCR定量细胞因子转录。三种高剂量的比较表明，在观察到的病变或寄生虫复制方面它们之间没有显着差异，所有这些都明显高于低剂量感染。相对于无挑战的对照，所有感染鸡的IFN-γ和IL-10的转录均增加，与剂量水平无显着差异（p> 0.05）。在三只鸡之间，在病变评分，寄生虫复制或盲肠细胞因子表达上没有发现显着差异。因此，我们建议4,000大肠杆菌卵囊足以在商业蛋鸡中可靠地诱发损伤，并且可以通过qPCR从这些相同的禽类中得出寄生虫复制的估计值。但是，更准确的量化艾美球虫复制需要一个单独的低剂量攻击组。在合适的鸡品系中优化激发剂量对于最大化蛋的价值至关重要。体内功效研究。对于球虫病，这种方法可以减少具有统计学意义的研究所需的鸡只数量，并降低实验严重性。