Inhibitory effect of Cnidium monnieri aqueous extract on Eimeria tenella infection in chicks

Eimeria tenella is the primary cause of cecal coccidiosis in broilers. This infection leads to severe intestinal inflammation and tissue damage, resulting in substantial economic losses to the poultry industry. The widespread use of chemical anticoccidials has led to serious drug resistance, thus creating an urgent need for the development of safe and natural alternatives. Cnidium monnieri (L.) Cusson, a traditional Chinese medicinal herb, possesses anti-inflammatory, antibacterial, and immunomodulatory properties. This study aimed to systematically evaluate the anticoccidial efficacy of the aqueous extract of Cnidium monnieri (CMAE) and to explore its mechanism of action both in vivo and in vitro.One hundred twenty one-day-old broilers were randomly divided into four groups: a negative control (CON), a positive control (PC or E. tenella infection), an E. tenella + CMAE group (E. tenella + CM), and an E. tenella + diclazuril group (E. tenella + DZ). In vivo experiments showed that the E. tenella + CM group achieved an anticoccidial index (ACI) of 161.5, demonstrating a moderate anticoccidial effect comparable to that of the E. tenella + DZ group (ACI = 160). Histopathological analysis revealed that the cecal villus length in the E. tenella + CM group was 12.5 ± 0.8 cm at 10 days post-infection (dpi) (8.2 ± 0.5 cm in the E. tenella group, P<0.01). Additionally, the infiltration of inflammatory cells in cecal tissues was reduced by 62.3 ± 4.1% (P<0.01). Serum enzyme-linked immunosorbent assay (ELISA) results demonstrated that, at 7 dpi, the serum levels of IgA (1.8 ± 0.2 μg/mL) and IgM (1.6 ± 0.1 μg/mL) in the E. tenella + CM group were significantly higher than the corresponding levels in the E. tenella group (P< 0.01). In vivo quantitative real-time polymerase chain reaction (qPCR) results indicated that CMAE, at the tested concentration, significantly downregulated the mRNA expression of pro-inflammatory cytokines (IL-1β, IL-6, IL-17, IL-22, TNF-α) in infected cells (by 38.7%-52.1%) while simultaneously upregulating the mRNA expression of anti-inflammatory cytokines (IL-10, TGF-β) (by 1.8- to 2.1-fold; P< 0.01). Western blot analysis further confirmed that CMAE significantly inhibited the activation of the NF-κB pathway: the phosphorylation level of p65 was reduced by 51.2 ± 3.4%, the phosphorylation level of IκB-α was reduced by 46.8 ± 2.9%, and the expression of the anti-apoptotic protein Bcl-2 was decreased by 39.5 ± 2.7% (P< 0.01). Flow cytometry analysis showed that, at 10 dpi, the peripheral blood CD4⁺/CD8⁺ T cell ratio in the E. tenella + CM group was 1.8 ± 0.1, which was significantly higher than that in the E. tenella group (P< 0.05) and comparable to the ratio in the CON group. In conclusion, the aqueous extract of Cnidium monnieri effectively mitigated the intestinal damage induced by Eimeria tenella in broiler chickens by inhibiting the NF-κB signaling pathway, modulating cytokine balance, and enhancing both humoral and cellular immunity. These findings suggest its significant potential as a natural anticoccidial agent, thereby providing a scientific basis for the prevention and control of coccidiosis in broiler chickens.