Submitted to: Medical and Veterinary Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/9/2004
Publication Date: 1/10/2005
Citation: Carroll, J.F., Klun, J.A., Debboun, M. 2005. Repellency of two species of ticks (Acari: ixodidae) by deet and SS220 applied to skin involves olfactory sensing. Medical and Veterinary Entomology. 19:101-106. Interpretive Summary: Ticks and tick-borne diseases, such as Lyme disease, are serious human health problems in the U.S. and most of the habitable world. Because area-wide tick programs are in limited use, repellents remain a last line of protection against tick bite. Deet, the most widely used tick repellent approved for use on skin is poorly understood in terms of the manner in which ticks sense and react to it. We tested whether blacklegged ticks, Ixodes scapularis, and lone star ticks, Amblyomma americanum, responded to deet and the ARS-developed repellent SS220 in the vapor phase, as well as on treated skin. Both species of ticks were repelled by both compounds through untreated cloth covering treated skin, indicating that they responded to air-borne repellent emanating from treated skin. In fingertip bioassays, SS220 on skin was as effective as deet in repelling both species of ticks. These findings are of interest to those in the field of medical entomology and public health and Department of Defense disease specialists. The development of new and more effective ways of using repellents can benefit all persons who enter tick habitats for work or recreation.
Technical Abstract: Responses of host-seeking nymphs of the blacklegged tick, Ixodes scapularis Say and lone star tick, Amblyomma americanum (L.) to the repellents N,N-diethyl-3-methylbenzamine (deet) and lS,2'S)-2 methylpiperidinyl-3-cyclohexene-1-carboxamide (SS220) were studied using fingertip laboratory bioassays. Ethanol solutions of both compounds applied to the skin strongly repelled both species of ticks at 0.8 and 1.6 umole of copound/cm2 of skin. The ticks were also repelled when two layer of orgndy cloth covered the portion of a finger treated with either deet or SS220. Gas chromatographic analyses of the outer layer of cloth that had covered skin treated with 1.6 umole compound/cm1 skin revealed only 0.1 nmole SS220/cm2 cloth and 2.8 nmole deet/cm1 cloth. However, in bioassays in which a single layer of cloth was treated with a dose of deet or SS220 equivalent to the amount found in the outer layer of cloth, ticks were not repelled. Results unequivocally demonstrated that these ticks responded to the repellents in the vapor phase when repellent treated skin was covered with cloth to obviate lactile contact with them, and made it clear that the ticks detect the repellents by olfactory sensing. Heretofore the mode of action of deet and SS220 was unclear.