Toxic and repellent activity of selected monoterpenoids (thymol, carvacrol and linalool) against the castor bean tick, Ixodes ricinus (Acari: Ixodidae)

• Published in: Veterinary parasitology 2017-10, Vol.245, p.86-91
• Main Authors: Tabari, Mohaddeseh Abouhosseini, Youssefi, Mohammad Reza, Maggi, Filippo, Benelli, Giovanni
• Format: Article
• Language: English
• Subjects: Acaricide; Acaricides - chemistry; Acaricides - pharmacology; Animals; Behavior, Animal - drug effects; Eco-friendly control; Insect Repellents - chemistry; Insect Repellents - pharmacology; Ixodes - drug effects; Larval packet test; Larvicidal toxicity; Monoterpene; Monoterpenes - chemistry; Monoterpenes - pharmacology; Ovum - drug effects; Permethrin - pharmacology; Repellent activity test; Thymol - chemistry; Thymol - pharmacology
• ISSN: 0304-4017; 1873-2550
• DOI: 10.1016/j.vetpar.2017.08.012

[Display omitted] •The effective and eco-friendly control of ticks is a major challenge for modern parasitology.•We studied the toxicity and repellent potential of several plant-borne monoterpenoids on Ixodes ricinus.•Thymol and carvacrol tested at low doses showed high ovicidal and larvicidal activity.•Both compounds tested at 0.25% led to repellency rates > 90% on I. ricinus larvae.•Linalool failed to show any toxic activity against ticks, repellency was limited. The castor bean tick, Ixodes ricinus, is a species of medical and veterinary importance. The use of synthetic acaricides for tick control has led to development of resistance, residues in the environment and animal products, and public health concerns. In this regard, plant essential oils and their main constituents represent an appealing alternative strategy to combat ticks. The phenols thymol and carvacrol and the alcohol linalool are monoterpenoids occurring in essential oils of several aromatic and medicinal plants, such as thyme, oregano, savory, lavender and coriander. Recent studies have shown toxicity of these monoterpenoids against selected mosquito vectors and other arthropod pests. However, information on their bioactivity on I. ricinus is not available. On this basis, here we evaluated the ovicidal, larvicidal and repellency effects of these compounds against I. ricinus. Concentrations of 0.25, 0.5, 1, 2 and 5% were sprayed on the egg masses, then hatching rates were noted. Larvicidal assays were conducted on unengorged larvae, following the larval packet technique. The repellency was determined by measuring the vertical migration behavior of ticks in laboratory conditions. Carvacrol and thymol at all concentrations tested led to a significant hatching decrease, showing an efficacy higher than permethrin, whereas linalool did not cause any significant effect. In the larvae treated with carvacrol and thymol (1, 2 and 5%), mortality rates reached 100% after 24h, showing a larvicidal efficacy higher than permethrin, whereas no effect was seen in the larval groups treated with linalool. Carvacrol and thymol at all concentrations tested showed >90% repellency on I. ricinus. Linalool was scarcely effective (50.24% repellency) only at the concentration of 5%. Overall, based on these results, the phenols carvacrol and thymol can be considered as candidate ingredients for the development of novel acaricidal formulations to control the populations of I. ricinus and the spread of related tick-b