Abstract
BackgroundThe limited ovicidal activity of currently available acaricides is a significant obstacle to efficacious scabies treatment. Several essential oils or their respective components have proved to be active against the eggs of arthropods, mainly lice and ticks. Information on the activity of these oils and/or components against the eggs of mites remains very limited. The aim of this study was to assess the activity of six terpenes (carvacrol, eugenol, geraniol, citral, terpinen-4-ol and linalool) commonly found in essential oils against the eggs of Sarcoptes scabiei.MethodsSarcoptes eggs were exposed to paraffin oil containing 1, 2.5, or 5% of each terpene tested. After a 12-h exposure period, the eggs were washed and placed in paraffin oil for hatching. Embryonic development following treatment was assessed every day to determine the stage of developmental arrest.ResultsThe median effective concentration to obtain 50% egg mortality (EC50) was 0.5, 0.9, 2.0, 4.8, 5.1 and 9.8% for carvacrol, eugenol, geraniol, citral, terpinen-4-ol and linalool, respectively. The microscopic images of eggs after each treatment indicated that these six terpenes may act by penetrating through the aeropyles on the egg surface.ConclusionsIn conclusion, carvacrol, eugenol and geraniol possess significant ovicidal activities, which should be considered as promising ovicidal agents for the treatment of scabies.Graphical
Highlights
The limited ovicidal activity of currently available acaricides is a significant obstacle to efficacious scabies treatment
To test the ovicidal activity of these compounds, Sarcoptes eggs at the early embryonic stage were placed on a microscope slide and exposed to paraffin oil containing 1, 2.5 or 5% of each terpene
Embryos in eggs exposed to 1% citral (Table 2, images 12–15) developed to a certain stage but stopped developing; embryos in eggs exposed to 1% carvacrol (Table 2, images 26–28), 1% eugenol (Table 2, images 20–22), 1% geraniol (Table 2, images 23–25) and 25% benzyl benzoate (Table 2, images 5–7) did not develop by 24 h, and the eggs remained at the early embryonic stage (Table 2)
Summary
The limited ovicidal activity of currently available acaricides is a significant obstacle to efficacious scabies treatment. Information on the activity of these oils and/or components against the eggs of mites remains very limited. Sarcoptes scabiei is a parasitic mite responsible for the skin disease called scabies. With an estimated 200 million people infected worldwide, scabies is one of the most prevalent infectious skin diseases [1]. It remains a major public health issue in many resource-poor areas. The limited ovicidal activity of these currently available acaricides has been and remains a significant obstacle for efficient scabies control. There is an urgent demand for novel drugs which can target the eggs of S. scabiei
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