Acaricidal activity against Ixodes ricinus nymphs of essential oils from the Libyan plants Artemisia herba alba, Origanum majorana and Juniperus phoenicea.

Fawzeia Elmhalli,Sandra L Baldauf,Giulio Grandi,Samira S Garboui,Anna Karin Borg Karlson,Raimondas Mozūraitis

doi:10.1016/j.vprsr.2021.100575

Abstract

Ixodes ricinus (L.) (Acari: Ixodidae) is a major vector for the transmission of several important human pathogens. The aim of the present study was to evaluate the in vitro efficacy of different concentrations of essential oils (Eos) on I. ricinus tick nymphs. Oils were obtained from the leaves of three plants native to Libya: white wormwood (Artemisia herba alba Asso), marjoram (Origanum majorana L.) and Arâr (Juniperus phoenicea L., English common name Phoenician juniper). Assays were done using the "open filter paper method". Two concentrations from each oil, 0.5 and 1μl/cm, were tested. The acaricidal effect was measured in terms of the lethal concentrations (LC50, LC95) and lethal time (LT50, LT95). Mortality rates were obtained by counting the surviving nymphs every 30min for the first five hours and then at 24, 48 and 72h. A mortality of 100% was recorded at the higher concentration of oils (1μl/cm2) from A. herba alba and J. phoenicea at the first 2h of exposure. Exposure to O. majorana led to 100% mortality on the third day (72h), and this effect decreased noticeably with 0.5μl/cm2 oil at the same exposure time. However, 50% of ticks showed a paralysis effect and less movement after 2h. The LC50 of mortality was reached within the first 24h of exposure time at 0.5μl/cm2 of O. majorana, which produced 60% tick's mortality. Chemical composition of the essential oils was elucidated by gas chromatography-mass spectrometry analyses. These results suggest that essential oils deserve further investigation as components of alternative approaches for I. ricinus tick control.

Highlights

The sheep tick, Ixodes ricinus (Acari: Ixodidae) is one of the most important vectors of tick-borne diseases to humans, at least in the northern hemisphere
We focused on three wild plants that are widely used in Arabian traditional medicine, as a source of green acaricidal substances against I. ricinus ticks
Our results show that A. herba alba, J. phoenicea, and O. majorana all have significant acaricidal effects on nymphs of I. ricinus

Summary

Introduction

The sheep tick, Ixodes ricinus (Acari: Ixodidae) is one of the most important vectors of tick-borne diseases to humans, at least in the northern hemisphere. I. ricinus can transmit Borrelia burgdorferi s.l., the agent of Lyme borreliosis (LB), for which 85,000 cases are reported every year in Europe (Lindgren and Jaenson, 2006). In southern Sweden it was reported an average incidence of 464 cases of erythema migrans per 100,000 person/year (period 1997–2003), while the mean incidence in Europe was lower (22.05/100000) (Makiello and Sykes, 2016). In addition approximately 5000–12,000 cases of tick-borne encephalitis (TBE) are reported in Europe each year (Zavadska et al, 2013), and in

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