Parasitology Department, Faculty of Veterinary Medicine, Beni-Suef University, Beni Suef, 62511, Egypt.
Zoology Department, Faculty of Science, Beni-Suef University, Beni Suef, Egypt.
Exp Appl Acarol. 2022 Jul;87(2-3):273-287. doi: 10.1007/s10493-022-00737-4. Epub 2022 Aug 6.
Ticks are of great economic importance worldwide, both because they represent major obstacles to livestock productivity and because of their ability to transmit diseases to humans and animals. Although synthetic acaricides are the most common method for tick control, their overuse has led to the development of resistance as well as unacceptable residual levels in animal products and in the environment in general. There is therefore an urgent need to identify alternative treatments. Among such alternative approaches for tick control is plant essential oil (EO) therapy. In the present study, we investigated the synergistic effect of EOs of three oregano species-Origanum onites, O. majorana and O. minutiflorum-against Rhipicephalus annulatus larvae. Gas chromatography-mass spectrometry profiles of the three EOs revealed that carvacrol was their major component, with a concentration of 86.2% in O. majorana, 79.1% in O. minutiflorum and 77.4% in O. onites. The results of larvicidal assays revealed that the doses that lead to the death of 50% of the ticks (LC) were 22.99, 25.08 and 27.06 µL/mL for O. majorana, O. minutiflorum and O. onites EOs, respectively, whereas the doses that lead to the death of 99% (LC) were 41.26, 43.62 and 48.96 µL/mL. In addition, the LC and LC of the three oils combined was lower (viz., 4.01 and 6.97 µL/mL) than that of each oil alone. The tested EOs were also able to repel larvae of R. annulatus to varying degrees, with O. onites oil exhibiting the greatest repellent effect, as shown by the lowest RC dose, followed by O. minutiflorum and O. majorana. Interestingly, this means that the oil that was least effective in killing the larvae was the most effective in repelling them. The calculated synergistic factor of any combination was higher than 1 which means that combinations have a synergistic effect. In conclusion, the combination of all three oils showed higher toxic and repellent activities than either oil separately or combinations of any two oils, suggesting synergistic effects with low doses. Further studies including field trials and the establishment of the mode of action and side effects are urgently needed to expand on these findings, and other tick stages such as adults should also be tested.
蜱虫具有重要的经济意义，因为它们不仅严重阻碍家畜的生产力，还能将疾病传播给人类和动物。尽管合成杀蜱剂是控制蜱虫最常用的方法，但由于过度使用，这些药剂已经导致了抗药性的产生以及在动物产品和环境中不可接受的残留水平。因此，迫切需要寻找替代疗法。植物精油（EO）疗法就是一种替代方法。在本研究中，我们研究了三种牛至属植物精油（O. onites、O. majorana 和 O. minutiflorum）对硬蜱幼虫的协同作用。三种精油的气相色谱-质谱图谱分析表明，香芹酚是它们的主要成分，在 O. majorana 中的浓度为 86.2%，在 O. minutiflorum 中的浓度为 79.1%，在 O. onites 中的浓度为 77.4%。幼虫杀灭试验结果表明，导致 50%的蜱虫死亡的剂量（LC）分别为 22.99、25.08 和 27.06 µL/mL，而导致 99%的蜱虫死亡的剂量（LC）分别为 41.26、43.62 和 48.96 µL/mL。此外，三种精油混合后的 LC 和 LC 比每种精油单独使用时的 LC 和 LC 更低（即 4.01 和 6.97 µL/mL）。测试的精油也能够在不同程度上驱赶硬蜱幼虫，其中 O. onites 精油表现出最强的驱避效果，其最低 RC 剂量表明其驱避效果最好，其次是 O. minutiflorum 和 O. majorana。有趣的是，这意味着在杀灭幼虫方面效果最差的油，在驱赶幼虫方面的效果最好。任何组合的协同因子都高于 1，这意味着组合具有协同作用。总之，三种油的组合表现出比任何一种油单独使用或两种油的组合更高的毒性和驱避活性，表明低剂量下具有协同作用。需要进一步的研究，包括田间试验和作用方式以及副作用的建立，以进一步扩展这些发现，还应该测试其他蜱虫阶段，如成虫。
