Study on In Vitro Acaricidal Proprieties of Pinus sylvestris Against Two Ectoparasites of Veterinary Importance Dermanyssus gallinae and Hyalomma scupense

The present study deals with the toxicity of Pinus sylvestris essential oil against red poultry mites Dermanyssus gallinae and Hyalomma scupense cattle ticks in laboratory condition. Individual essential oil components identified using a gas chromatograph/mass spectrometer, namely α-pinene (44.92%), β-pinene (17.51%), δ-3 carene (16.18%) and D -Limonene (9.21%) were tested as well as. For this purpose, different doses (0.31; 0.62; 1.25 and 2.5 mg/mL) of essential oil and four monoterpenes using mites contact and spraying in vitro bioassays were carried out. Amitraz and thymol (positive controls), and ethanol and distilled water (negative controls) were also tested each with three replications. Tick larvicidal and ovicidal assays were done testing 0.5; 1; 2 and 4 mg/mL of the P. sylvestris essential oil and its main components. The experiment results from mites revealed that the spraying application method was more effective than the contact bioassay for acaricidal property when P. sylvestris essential oil was toxic to D. gallinae with LC 50 values of 0.68 mg/mL. Larvicidal and ovicidal assays revealed the promising activity of the essential oil against tick larvae and eggs. Among all the tested compounds, D -Limonene appears as the most toxic essential oil constituent for both ticks and mites, showing LC 50 values lower than the whole essential oil. δ-3-carene was slightly toxic, with LC 50 values higher than the whole essential oil, whereas α-pinene and β-pinene showed weak acaricidal activity even at high concentration. On the other hand, P. sylvestris essential oil and its principal components were tested for acetyl-cholinesterase inhibitory activity using Ellman’s colorimetric method and compared to a reference galantamine. Interestingly the monoterpene D -Limonene was found the most active AchE inhibitor (IC 50 = 27.22 µg/mL), almost comparable to that of positive control. Overall, our research pointed out the importance of the traditional use of P. sylvestris as an ecofriendly alternative against ectoparasites of veterinary importance; D. gallinae and H. scupense . In vivo trials should also be conducted to assure the safe use of natural plants. Graphical Abstract