Abstract
Globally, the economic losses due to hard ticks infestation and the control of the associated diseases have been calculated at USD $13.9–18.7 billion per year. The economic impact is related to its direct damage to the skins, blood loss, anemia, severe immunological reactions and indirect losses that related to the effects of hemoparasites, cost of treatment for clinical cases and expenses incurred in the control of ticks. The current study evaluated the acaricidal activities of fennel Foeniculum vulgare essential oil and its main components; trans-anethole and fenchone; against R. annulatus. GC–MS analysis revealed that this oil contained 16 components representing 99.9% of the total identified compounds with E-anethole being the predominant component(64.29%), followed by fenchone (9.94%). The fennel oil and trans-anethole showed significant acaricidal activities. The LC50 of the fennel oil was attained at concentrations of 12.96% for adult ticks and 1.75% for tick larvae meanwhile the LC50 of trans-anethole was reached at concentrations of 2.36% for adult tick and 0.56% for tick larvae. On the contrary, fenchone showed no any significant adulticidal activities and its LC50 attained at a concentration of 9.11% for tick larvae. Regarding repellence activities, trans-anethole achieved 100% repellency at the concentration of 10% while fennel showed 86% repellency at the same concentration. Fenchone showed no repellency effect. Treatment of larvae with fennel, trans-anethole, and fenchone LC50 concentrations significantly inhibited the acetylcholinesterase activity. Meanwhile, glutathione s-transferase activity was significantly decreased in fennel treated larvae but no significant effect was found in the larvae of trans-anethole and fenchone groups. These results indicate that the acaricide effect of fennel oil may attributed to its high content of trans-anethole. This was supported by potent adulticidal, larvicidal, and repellency effects of trans-anethole against Rhipeciphalus annulatus tick and therefore it could be included in the list of acaricide of plant origin.
Highlights
Cattle tick is a major threat to cattle production and health condition globally
Trans-anethole showed significant acaricidal activity especially at concentrations of 5 and 10% with tick mortality rate reached to 82.67 and 100% respectively and LC50 achieved at a concentration of 2.36% (Fig 3)
The increasing resistance of ticks to these acaricides in addition to the problems associated with their meat and milk residues and potential toxicity on non-target organisms have become significant challenges to the Groups Control untreated Deltamethrin Fennel Trans-anethole Fenchone
Summary
Cattle tick is a major threat to cattle production and health condition globally. Ticks infestation causes significant loss in meat, milk, and leather production [1]. Tick-borne diseases to cattle as babesiosis and anaplasmosis are the major health obstacles to effective livestock production [2]. Chemical acaricides are the most common approach for tick control. This strategy of control has several issues on public health hazards through residues and acaricides resistance [3]. Plant metabolites and essential oils are considered a suitable alternatives for ticks’ control [4, 5] as it is safe for public health and the environment [6]
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