Repellency Effect of Essential Oils of some Native Plants and Synthetic Repellents against Human Flea, Pulex irritans (Siphonaptera: Pulicidae)

Background: Fleas are important vectors of human and animal disease, and control measures for protection against their bites and flea-borne diseases are necessary.

Methods: The essential oils (EOs) of four native medicinal plants, Ziziphora tenuiore, Myrtus communis, Achillea wilhelmsii and Mentha piperita were isolated by hydrodistillation technique and analyzed by GC-MC. The repellent activity of EOs and synthetic compounds, DEET and permethrin, were assayed on human subjects against field collected fleas. The effective doses of 50% and 90% of EOs and synthetic compounds were estimated by probit analysis of dose and response regression line.

Results: Analysis of EOs revealed about 19 major components. All oils were found to be more repellent (ED₅₀ range= 208-955μg cm^-2) than DEET and permethrin (ED₅₀ range= 27-182 × 10³μg cm^-2). Thyme and myrtle oils showed high repellent activities and among the total detected terpenes, thymol (36.26%) and α-pinene (32.5%) were the major components of those oils respectively.

Conclusion: Low repellent potency of DEET and permethrin against fleas might be related to flea olfactory system and further molecular and electrophysiological studies are required to conceive new ideas for the discovery and development of the next generation of repellents. Based on high repellent activity of thyme and myrtle essential oils against Pulex irritans further studies should be staged to develop their appropriate effective formulations. Likewise, field trials should be carried out to evaluate the operational feasibility and dermal toxicity over a long period.