Anthelmintic activity of winter savory (Satureja montana L.) essential oil against gastrointestinal nematodes of sheep

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, due to their numerous advantages. The present study aimed to evaluate the possibility of using winter savory (Satureja montana L.) EO against sheep GINs. The chemical composition of the tested oil was determined by gas chromatography-mass spectrometry (GC-MS). The efficacy of the tested oil was determined in vitro using the egg hatch test (EHT), and in vivo using the faecal egg count reduction test (FECRT) performed in two farms. Preliminary toxicity studies including clinical observation, haematological and biochemical blood analysis were also performed to evaluate the safety of the tested oil to the hosts. In addition, a coproculture study was carried out in the tested farms using the appropriate morphological keys. 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 (R-2 = 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. No significant changes (p > 0.05) in the percentage representation of GIN genera were observed in the coproculture study, indicating that the treatment agent was not specific to a single genus. Conclusion The anthelmintic potential showed 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. However, further studies should be conducted to increase efficacy in field conditions.