Soutter Francesca, Werling Dirk, Kim Sungwon, Pastor-Fernández Iván, Marugán-Hernández Virginia, Tomley Fiona M, Blake Damer P
Department of Pathobiology and Population Sciences, Royal Veterinary College, London, United Kingdom.
SALUVET, Animal Health Department, Faculty of Veterinary Sciences, Complutense University of Madrid, Madrid, Spain.
Front Vet Sci. 2021 Feb 22;8:640041. doi: 10.3389/fvets.2021.640041. eCollection 2021.
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 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 (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 ( > 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 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 replication requires a separate low dose challenge group. Optimisation of challenge dose in an appropriate chicken line is essential to maximize the value of efficacy studies. For coccidiosis, this approach can reduce the numbers of chickens required for statistically significant studies and reduce experimental severity.
某些种类的寄生虫感染鸡的胃肠道，引发疾病并影响生产。家禽业依靠抗球虫药物和活疫苗来进行防控，因此需要新型、可扩展的替代方法。了解商品鸡实验性感染的结果对于评估新型干预措施很有价值。我们研究了三种商品蛋鸡品系中不同感染剂量（一种低剂量、三种高剂量）的影响，评估盲肠中的病变评分、寄生虫复制和细胞因子反应。将八到十只鸡分组饲养，并在21日龄时用250、4000、8000或12000个孢子化卵囊进行感染。感染后五天，评估盲肠病变，并通过qPCR定量寄生虫复制，通过RT-qPCR定量细胞因子转录。对三种高剂量进行比较发现，观察到的病变或寄生虫复制在它们之间没有显著差异，且均显著高于低剂量感染。与未受挑战的对照相比，所有感染鸡的IFN-γ和IL-10转录均增加，且与剂量大小无关（P>0.05）。在三个鸡品系之间，病变评分、寄生虫复制或盲肠细胞因子表达未检测到显著差异。因此，我们认为4000个卵囊是在商品蛋鸡中可靠诱导病变的足够剂量，并且可以通过qPCR从这些鸡中获得寄生虫复制的估计值。然而，更准确地定量寄生虫复制需要一个单独的低剂量挑战组。在合适的鸡品系中优化挑战剂量对于最大化球虫病疗效研究的价值至关重要。对于球虫病，这种方法可以减少统计学上有意义的研究所需的鸡数量，并降低实验强度。
