The phytotherapy properties of winter savory (Satureja montana L.) essential oil against gastrointestinal nematodes of sheep

Abstract

Background: The increasing difficulties in combating anthelmintic resistance in gastrointestinal nematodes (GINs) of sheep worldwide and the residues of chemical drugs in animal products and the environment necessitate the search for alternatives. Previous studies have shown that plant essential oils (EOs) could be valuable anthelmintic agents. The aim of this study was to evaluate the possibility of using winter savory (Satureja montana L.) EO against sheep GINs through performing in vitro and in vivo efficacy tests and preliminary toxicity studies. Methods: The chemical composition of the S. montana EO was determined by gas chromatography-mass spectrometry (GC-MS). For the evaluation of anthelmintic potential in vitro, the Egg Hatch Test (EHT) was performed at eight different concentrations (50, 12.5, 3.125, 0.781, 0.195, 0.049, 0.025 and 0.0125 mg/ml). Field efficacy was evaluated using the Faecal Egg Count Reduction Test (FECRT) on two farms where the oil was applied intraruminally to sheep at a mean dose of 150 mg/kg. The toxic effect of the oil was evaluated by physical observation of the tested animals and by collecting blood samples for further haematological and biochemical analyses. Coproculture examination of faecal samples from the tested sheep before and after treatment was also performed to identify the GIN genera present. Results: Main compounds of the S. montana oil identified by GC-MS analysis were p-cymene (42.8%), carvacrol (28.1%) and y-terpinene (14.6%). The in vitro EHT showed a dose-dependent (R²=0.94) anthelmintic potential of the tested oil with ovicidal activity varying from 17.0-83.3% and determined IC₅₀ value of 0.59 mg/ml. The field efficacy reached 33% (at group level) and 50% (at individual level) at D14 after treatment. In vivo efficacy was significantly higher in farm 2 (FEC above 65% at group level, p<0.05) where sheep were kept in pens during treatment. No toxic effects were observed either in the physical observation of the test animals or in their liver and kidney function. Conclusion: The moderate efficacy on EHT and FECRT, without adverse effects on the sheep, suggests that S. montana EO is suitable for the control of sheep GINs as part of an integrated parasite management. Further studies should be conducted to further increase efficacy.