ECOLOGICAL, CHEMICAL AND MOLECULAR APPROACHES TO REDUCING TICK BITES AND TICK-BORNE DISEASES
Title: Elemol and Amyris Oil Repel the Ticks Ixodes scapularis and Amblyomma americanum (Acari: Ixodidae) in Laboratory Bioassays
Submitted to: Experimental and Applied Acarology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 24, 2009
Publication Date: December 18, 2009
Citation: Carroll, J.F., Paluch, G., Coats, J., Kramer, M.H. 2009. Elemol and amyris oil repel the ticks Ixodes scapularis and Amblyomma americanum (Acari: Ixodidae) in laboratory bioassays. Experimental and Applied Acarology. 51(4)383-392.
Interpretive Summary: Tick-borne diseases pose a serious threat to humans throughout much of the habitable world. Repellents provide a critical means of personal protection against tick bite. The oil extracted from balsamic torchwood, Amyris balsamifera, and some of its constituent compounds have been shown to repel mosquitoes. Elemol occurs in the Osage orange, Maclura pomifera, a small tree native to the central U. S, also repels mosquitoes. We evaluated amyris oil and elemol as tick repellents in laboratory bioassays against blacklegged ticks (a.k.a. deer ticks) and lone star ticks, vectors of Lyme disease and human monocytic ehrlichiosis, respectively. Both elemol and amyris oil were repellent to both species of ticks. Amyris oil was as effective against lone star ticks as the widely used repellent deet. These findings are of interest to researchers involved in repellent discovery and development.
The essential oil from Amyris balsamifera (Rutaceae) and elemol, a principal constituent of the essential oil of Osage orange, Maclura pomifera (Moraceae) were evaluated in in vitro and in vivo laboratory bioassays for repellent activity against host-seeking nymphs of the blacklegged tick, Ixodes scapularis, and the lone star tick, Amblyomma americanum. Both bioassays were based on the tendency of these host-seeking ticks to climb. In one bioassay, the central portion of a vertical strip of filter paper was treated with test solution and ticks placed or allowed to crawl onto the untreated lower portion. In the other bioassay, a strip of organdy cloth treated with test solution was doubly wrapped (treatment on outer layer) around the middle phalanx of a forefinger and ticks released on the fingertip. Both amyris oil and elemol were repellent to both species of ticks. Elemol did not differ significantly in effectiveness against A. americanum than the widely used repellent deet. At 2 and 4 h after application to filter paper, 10% amyris oil solutions repelled 80% and 55%, respectively, of A. americanum nymphs. Ixodes scapularis was repelled by lower concentrations of amyris oil and elemol than A. americanum.