Investigating the effects of essential oils and pure botanical compounds against Eimeria tenella in vitro

Essential oils (EO) and natural bioactive compounds are well-known antibacterial and anti-inflam-matory factors; however, little is known about their anti-coccidial activity and mode of action. EO deriving from basil (BEO), garlic (GAR), oregano (OEO), thyme (TEO), and their main bioactive compounds were inves-tigated for their anticoccidial proprieties and compared to salinomycin (SAL) and amprolium (AMP) in vitro. The invasion of Eimeria tenella sporozoites was studied on 2 cell models: Madin-Darby Bovine Kidney (MDBK) cells and primary chicken epithelial cells (cIEC). Invasion efficiency was evaluated at 2 and 24 h postinfection (hpi) with counts of extracellular sporozoites and by detection of intracellular E. tenella DNA by PCR. Results show that at both timepoints, the EO were most effective in preventing the invasion of E. tenella with an average reduction of invasion at 24 hpi by 36% in cIEC and 55% in MDBK. The study also examined cytokine gene expression in cIEC at 24 hpi and found that AMP, BEO, OEO, TEO, carvacrol (CAR), and thymol (THY) sig-nificantly reduced interleukin (IL)8 expression, with CAR also reducing expression of IL1b and IL6 compared to the infected control. In addition, this work investigated the morphology of E. tenella sporozoites treated with anticoccidial drugs and EO using a scanning electron microscope. All the treatments induced morphological anomalies, characterized by a reduction of area, perimeter and length of sporozoites. SAL had a significant impact on altering sporozoite shape only at 24 h, whereas CAR and THY significantly compromised the morphology already at 2 hpi, compared to the untreated control. OEO and GAR showed the most significant alterations among all the treatments. The findings of this study high-light the potential of EO as an alternative to traditional anticoccidial drugs in controlling E. tenella invasion and in modulating primary immune response.

Automated summary

Essential oils and natural bioactive compounds have been found to have anti-parasitic activity against Eimeria tenella and can modulate the immune response. They are potential alternatives to traditional drugs in controlling parasite invasion.