The symbiosis of host and intestinal microbiota constitutes a microecosystem and plays an important role in maintaining intestinal homeostasis and regulating the host's immune system. Eimeria tenella , an obligate intracellular apicomplexan parasite, can cause coccidiosis, a serious intestinal disease. In this study, the effects of E. tenella infection on development parameters (villus height, crypt depth, mucosa thickness, muscularis thickness, and serosa thickness) and microbiota in chicken cecum were investigated. Fourteen-day-old male Hy-Line Variety Brown layer chickens were inoculated with sporulated oocysts of E. tenella . Cecal tissues were collected 7 d after inoculation. Relative density of goblet cells and glycoproteins were determined by Alcian blue periodic acid–Schiff staining and periodic acid–Schiff staining, respectively. Intestinal development parameters were also evaluated. Cecal contents were extracted, and the composition of cecal microflora was examined by Illumine sequencing in the V3–V4 region of the 16S rRNA gene. Results indicated that E. tenella infection destroyed the structure of cecal tissue and reduced the relative density of goblet cells and glycoproteins. Sequencing analysis indicated that E. tenella infection altered the diversity and composition of cecal microbiota. The populations of Proteobacteria , Enterococcus , Incertae , and Escherichia–Shigella decreased, and those of Bacteroidales and Rikenella significantly increased in the infected group compared with those in the control group. Hence, the pathological damage caused by E. tenella infection is associated with cecal microbiota dysbiosis, and this finding may be used to develop an alternative measure for alleviating the effect of coccidiosis on the poultry industry.

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Eimeria tenella is an obligate intracellular parasite of the chicken cecum; it brings huge economic loss to the chicken industry. Enolase is a multifunctional glycolytic enzyme involved in many processes of parasites, such as infection and migration. In this study, the effect of diclazuril on the expression of enolase in second-generation merozoites of E. tenella ( Et ENO ) was reported. The prokaryotic expression plasmid pET-28a- Et ENO was constructed and transformed into Escherichia coli BL21 (DE3). Then, it was subjected to expression under the induction of isopropyl-β-D-1-thiogalactopyranoside. The expressed products were identified and purified. The purified Et ENO protein was used for antibody preparation. The Et ENO mRNA and protein expression levels were analyzed via real-time PCR and Western blotting. Localization of Et ENO on the merozoites was examined by immunofluorescence technique. The mRNA and protein expression levels of Et ENO were decreased by 36.3 and 40.36%, respectively, by diclazuril treatment. Et ENO distributed in the surface, cytoplasm, and nucleus of the infected/control group. With diclazuril treatment, it was significantly reduced in the surface and cytoplasm and even disappeared in the nucleus of the infected/diclazuril group. These observations suggested that Et ENO may play an important role in mechanism of diclazuril anticoccidial action and be a potential drug target for the intervention with E. tenella infection.

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Background: Diclazuril is a classic anticoccidial drug. The key molecules of diclazuril in anticoccidial action allows target screening for the development of anticoccidial drugs. In the present study, a diclazuril anticoccidiosis animal model was established, and the transcription and translation levels of the CDK-related kinase 2 of Eimeria tenella (EtCRK2) were detected through quantitative real-time PCR and Western blot analysis, respectively. The localisation of EtCRK2 in merozoites was examined with immunofluorescence techniques.Results: The mRNA and protein expression levels of EtCRK2 decreased in the infected/diclazuril group compared with those in the infected/control group. In addition, immunofluorescence analysis showed that EtCRK2 was localised in the cytoplasm of the merozoites. The fluorescence intensity of EtCRK2 in the infected/diclazuril group was significantly weaker than that in the infected/control group.Conclusions: The anticoccidial drug diclazuril against E.tenella affects the expression pattern of EtCRK2 molecule, and EtCRK2 is a potential target for new drug development.