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Toxicity against Ixodes ricinus nymphs of essential oils from the Libyan plants Artemisia herba alba, Origanum majorana and Juniperus phoenicea
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Systematic Biology. uppsala university.ORCID iD: 0000-0001-9341-2052
Department of Environmental Health, Faculty of Public Health, University of Benghazi, Benghazi, Libya. .
Department of Chemistry, School of Engineering Sciences in Chemistry, Biotechnology and Health, Royal Institute of Technology, Stockholm, Sweden..
Department of Zoology, Stockholm University, Stockholm, Sweden.
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

ABSTRACT Ixodes ricinus (L.) (Acari: Ixodidae) is a major vector for the transmission of several important human pathogens. The aim of the 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. And the toxic 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 30 minutes for the first five hours and then at 24, 48 and 72 h. A mortality of 100% was recorded at the higher concentration of oils (1µl/cm²) from A. herba alba and J. phoenicea at the first 2 hours of exposure. With O. majorana 100% mortality was only reached 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 2 hours. Whereas the LC50 of mortality was reached within the first 24h of ET 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 merit further investigation as components of alternative approaches for I. ricinus tick control.

 

Keywords [en]
Libyan plants, Artemisia herba alba, Origanum majorana, Juniperus phoenicea, Acaricidal, Ixodes ricinus.
National Category
Zoology
Research subject
Biology with specialization in Systematics
Identifiers
URN: urn:nbn:se:uu:diva-381133OAI: oai:DiVA.org:uu-381133DiVA, id: diva2:1302331
Available from: 2019-04-04 Created: 2019-04-04 Last updated: 2019-04-12
In thesis
1. Plants as Sources of Natural and Effective Acaricides: Against Ixodes ricinus  (Acari: Ixodidae)
Open this publication in new window or tab >>Plants as Sources of Natural and Effective Acaricides: Against Ixodes ricinus  (Acari: Ixodidae)
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Ticks and tick-borne diseases are major health hazards worldwide, with increasing numbers of cases of Lyme disease and tick-borne encephalitis reported yearly. Meanwhile, concerns about the environmental impact and safety of chemical acaricides are driving research into alternative control methods, such as plant-based acaricides. I evaluated eight plant species for their toxicity and repellency against nymphs of Ixodes ricinus (Acari: Ixodidae), the most important life cycle stage of tick-borne infection of humans.

Paper I examines the toxicity of the principal active component of the essential oil (EO) of lemon eucalyptus (Corymbia citriodora), p-menthane-3,8-diol (PMD). At 4 h of exposure time (ET), lethal PMD concentrations for 50% mortality (LC50) were 0.035–0.037 mg/cm² and for 95% mortality (LC95) were 0.095-0.097 mg/cm². For 0.1 mg/cm², lethal times for 50% mortality (LT50) were 2.1-2.8 h and for 95% mortality (LT95) were 3.9-4.2 h. An open filter assay gave the most consistent results of five methods tried. Paper II investigated the toxicity of ylang-ylang oil (YYO) and star anise oil (SAO), two naturally occurring, commercially available and inexpensive EOs. Oils were tested at 0.05, 0.1, 0.2, and 0.4μl/cm², and dead nymphs counted at 30-min intervals up to 5h and then at 24, 48 and 72h. For YYO, an exposure of 4.4h resulted in LC95 for 0.4 μl/cm² and LC50 for 0.2μl/cm². The LT95 was 3h for 0.4 μl YYO/cm² and 4.3 h for 0.2 μl/cm². For SAO, the highest concentration (0.4 μl/cm²) only reached LC50 at 14 h and LT95 was 24h. Thus, YYO is a much stronger acaricide but SAO still showed significant toxicity.

Paper III investigated two plants of traditional medicinal or economic importance in Libya -Salvadora persica, (Miswak) and Rosmarinus officinalis (Libyan Rosemary). EOs were extracted from wild-collected leaves by steam distillation. Oils were tested on I. ricinus nymphs and their chemical composition analysed by GC-MS. R. officinalis EO at 0.5 and 1µl/cm² exhibited 20% and 100% mortality, respectively, after about 5h of ET. The LC50 and LC95 for 1µl/cm² R. officinalis oil were 0.7 and 0.95 µl/cm², respectively. S. persica oil at 1µl/cm² gave 95% repellency up to 1.5h, reducing to 50% at around 5.45 h, but no significant mortality even after 24h ET. GC-MS analysis showed both oils to be rich in the monoterpenes 1,8 cineol, α-pinene and β-pinene with values of 20.8%, 5.9% and 16.8 %, respectively, for S. persica and 24.07%, 13.03% and 2.45%, respectively, for R. officinalis.

Paper IV investigated EOs extracted from leaves of three additional native Libyan plants - Artemisia herba alba (white wormwood), Origanum majorana (oregano) and Juniperus phoenicea (Ar-aar). At 1µl/cm², the LT95 for both A. herba and J. phoenicea EO was 2h versus 72 h for O. majorana oil. GC-MS analyses gave plant specific combinations of the monoterenoids α-pinene, 1,8-cineol, camphor, linalool, terpinene-4-ol, α-terpinol, β-caryophyllene and β-thujanone. EO of A.herba alba contained most of the oxygenated monoterpenes, which all are all known to have insecticidal activity.

Taken together, all the EOs used in this study show a broad spectrum of effects against I. ricinus nymphs, making them good candidates for controlling ticks and, thereby, the diseases they carry.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2019. p. 62
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1797
Keywords
Acaricidal, Ixodes ricinus, Libyan plants, essential oils, Plant-derived acaricides.
National Category
Biological Systematics
Research subject
Biology with specialization in Systematics
Identifiers
urn:nbn:se:uu:diva-381142 (URN)978-91-513-0629-2 (ISBN)
Public defence
2019-05-28, Lindahlsalen, Evolutionary Biology Center, Uppsala University, Norbyvägen 18D, Uppsala, 13:00 (English)
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Supervisors
Available from: 2019-05-02 Created: 2019-04-04 Last updated: 2019-06-17Bibliographically approved

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