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Abstract The economic losses caused by gastrointestinal nematodes of small ruminants are increasing today due to the development of anthelmintic resistance. Therefore, researchers from different parts of the world are searching for new, alternative strategies to control these parasites. As a valuable natural resource, medicinal plants and their products have emerged as a viable option. The aim of this study was to evaluate in vitro ovicidal activity of two chemotypes of the yarrow (Achillea millefolium L.) essential oil against sheep gastrointestinal nematodes. For this purpose, nematode eggs were collected from naturally infected sheep of two farms located in Southern Italy to perform the egg hatch test. In both farms, the coproculture examination identified the presence of four genera of sheep GINs: Haemonchus, Trichostrongylus, Teladorsagia and Chabertia. Main components of the yarrow essential oil identified by GC-MS analysis were 1,8-cineole (41.69%), camphor (8.37%) and trans-chrysanthenyl acetate (4.90) for the type 1 and β-pinene (28.53%), β-caryophyllene (18.71%) and 1,8-cineole (11.69%) for the type 2. In vitro ovicidal activity was evaluated at six different concentrations (50, 12.5, 3.125, 0.781, 0.195 and 0.049 mg/mL), whereby the inhibitory effect of the essential oil (Achillea millefolium L.) on egg hatchability varied from 46.5-99.5% (type 1) and 69.6-97.25% (type 2) and all concentrations tested showed a significantly higher efficacy compared to the negative control (p0.05) to the positive control (98.0%) at concentrations of 50 mg/mL (99.5%), 12.5 mg/mL (98.0%) and 3.125 (95.25%) of the type 1, and at concentrations of 50 mg/mL (97.25%) and 12.5 mg/mL (90.0%) of the type 2. The obtained results suggested that the A. millefolium essential oil has high anthelmintic potential, especially azulene-free chemotype rich in 1,8-cineole and camphor, which requires confirmation in further in vivo studies.

Herbal products such as essential oils may play a promising role in the treatment of infections caused by gastrointestinal nematodes (GINs). The aim of this study was to evaluate the in vitro potential of 11 essential oils (EOs) and one binary combination of isolated EO compounds, as well as the in vivo anthelmintic efficacy of two EO formulations. Four GIN genera were identified in the coproculture examination: Haemonchus, Trichostrongylus, Teladorsagia and Chabertia. The in vitro egg hatch test (EHT) was performed at six different concentrations (50, 12.5, 3.125, 0.781, 0.195 and 0.049 mg/mL) for each EO, whereas in the in vivo faecal egg count reduction test (FECRT), each EO sample was diluted in sunflower oil and orally administrated at a dose of 100 mg/kg to the different group of animals. In the EHT, the EOs of Origanum vulgare, Foeniculum vulgare, Satureja montana, Satureja hortensis and two types of Thymus vulgaris were the most effective. The dominant compounds of these EOs were carvacrol, thymol, anethol, p-cymene and γ-terpinene, indicating their importance for the anthelmintic activity. In the FECRT, both T. vulgaris EO type 1 and linalool:estragole combination show an anthelmintic potential with a mean effect on FECR of approximately 25%. The results suggest the possible role of tested EOs as anthelmintic agents in sheep farms, although further in vivo tests are needed.