Abstract
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 (p<0.0001). Furthermore, the inhibitory effect on egg hatching was similar (p>0.05) 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.
Highlights
Gastrointestinal nematodes (GIN) nowadays present a major problem faced by sheep producers worldwide (Sweeney et al, 2016; Kaplan et al, 2020)
Nematode eggs obtained from the faeces of naturally infected sheep on two farms located in Southern Italy were subjected to the egg hatch test
Qualitative and semi-quantitative chemical characterization of essential oils (EOs) was done by gas chromatography (GC) and mass spectrometry (MC), using Agilent Technologies 6890N gas chromatography coupled with Agilent Technologies 5975B electron ionization mass-selective detector
Summary
Gastrointestinal nematodes (GIN) nowadays present a major problem faced by sheep producers worldwide (Sweeney et al, 2016; Kaplan et al, 2020) Their parasitism leads to various negative effects in animals such as impaired health, reduced food intake, weight loss, weakness as well as low production and fertility which results in significant economic losses (Macedo et al, 2010; Dambola et al, 2018). The true, total costs of gastrointestinal parasitism in sheep, especially after the development of anthelmintic resistance, are likely to be much larger For these reasons, researchers around the world are focused on devising new, alternative strategies including genetic resistance control, pasture management, crop-livestock integration, nutrition adjustment, biological regulation (use of fungi and bacteria), vaccine production and some others (Zeineldin et al, 2018; Pinto et al, 2019)
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