The major clinical signs of coccidiosis in chickens due to Eimeria parasite are diarrhea and bloody feces. Previous studies showed that the impairment of the intestinal epithelial barrier and the elevation of the intestinal permeability are causes of clinical signs associated with coccidia challenges. Nevertheless, the information about molecular changes of the epithelial barrier at the early stage of the infection with a specific Eimeria species has not been mentioned. Hence, this study aims to elucidate the temporal relationships between epithelial barrier conditions and clinical signs in chickens infected with Eimeria tenella over the time from the earliest stages of infection.

White Leghorn chickens were inoculated with 1 × 10⁴ oocysts of E. tenella. Thereafter the chickens were monitored for their daily clinical signs through observation, and between 5 dpi to 10 dpi, feces were collected for oocysts counting. Chickens were then administrated with fluorescein isothiocyanate-dextran (FITC-d) for gastrointestinal permeability test and tissues were collected each day for histopathological observation and total RNA extraction. Finally, the mRNA expression levels of the tight and adherens junction genes and cytokine genes were evaluated using the quantitative real-time polymerase chain reaction (qRT-PCR).

In this study, clinical signs such as diarrhea and bloody feces were observed concurrently from 3 to 8 dpi. Histopathology changes such as severe inflammation, hemorrhage, and epithelial desquamation were identified in the cecum specimens. The FITC-d level in the E. tenella-infected group was significantly higher than in the control group. In the infected group, the expression of claudin-2 gene was also upregulated, whereas the expressions of claudin-3 and E-cadherin genes were decreased as compared to the control group. These results implied that clinical signs of avian coccidiosis were associated with the intestinal barrier disruption via changes in expression levels of claudins and E-cadherin at the intestine.

由艾美球虫引起的鸡球虫病的主要临床症状是腹泻和血便。先前的研究表明，肠上皮屏障的损害和肠通透性的升高是与球虫感染相关的临床症状的原因。然而，尚未提及有关特定艾美球虫感染早期上皮屏障分子变化的信息。因此，本研究旨在阐明感染艾美球虫的鸡在感染早期阶段的上皮屏障状况与临床症状之间的时间关系。

^{用 1 × 10 4的}E.tenella卵囊接种白来亨鸡。此后，通过观察监测鸡的日常临床症状，并在 5 dpi 至 10 dpi 之间收集粪便用于卵囊计数。然后给鸡施用异硫氰酸荧光素-葡聚糖（FITC-d）进行胃肠通透性测试，每天收集组织进行组织病理学观察和总RNA提取。最后，使用定量实时聚合酶链反应 (qRT-PCR) 评估紧密连接和粘附连接基因和细胞因子基因的 mRNA 表达水平。

在这项研究中，在 3 至 8 dpi 期间同时观察到腹泻和血便等临床症状。在盲肠标本中发现了组织病理学变化，例如严重的炎症、出血和上皮脱屑。E.tenella感染组的 FITC-d 水平显着高于对照组。与对照组相比，感染组claudin-2基因的表达也上调，而claudin-3和E-cadherin基因的表达降低。这些结果表明，禽球虫病的临床症状与肠道屏障破坏有关，通过改变肠道中密闭蛋白和 E-钙粘蛋白的表达水平。