Submitted to: Journal of Medical Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/26/2010
Publication Date: 7/1/2010
Citation: Carroll, J.F., Benante, J.P., Kramer, M.H., Lohmeyer, K.H., Lawrence, K. 2010. Formulations of Deet, Picaridin and IR3535 applied to skin repel nymphs of the Lone Star Tick (Acari: Ixodidae) for 12 hours. Journal of Medical Entomology. 47(4):699-704. Interpretive Summary: Tick-borne diseases are a serious threat to humans throughout much of the habitable world. Repellents are an important means of personal protection against tick bite. To determine the efficacies of some new formulations of approved repellents, we conducted a 12-hour trial using 17 human volunteers in cooperation with the Walter Reed Army Institute of Research. Twenty percent picaridin spray, 20% IR3535 spray, 20% picaridin lotion, 10% IR3535 spray and 33% deet cream (the standard US military repellent) were tested against host-seeking nymphs of the lone start tick. All formulations containing at least 20% active ingredient were highly effective, with more than 90% of the ticks repelled throughout the 12 hours. These results are of interest to the Department of Defense, repellent manufacturers and researchers in the field of repellent discovery and development.
Technical Abstract: The efficacies of a 20% 1-methyl-propyl-2-(hydroxyethyl)-1-piperidinecarboxylate (picaridin) spray, 20% 3-(N-acetyl-N-butyl)aminopropionic acid ethyl ester (IR3535) spray, 20% picaridin lotion, 10% IR3535 lotion, and 33% N,N-diethyl-3-methylbenzamide (deet) cream in repelling nymphal lone star ticks, Amblyomma americanum (L.), were determined at 2-h intervals over 12 h using human subjects. A repellent formulation was applied in a 5-cm wide band encircling a volunteer’s lower leg. For each challenge, 70 host-seeking nymphs were released on each volunteer’s ankle and tick locations were recorded 10 min after the ticks were released. Ticks that did not crawl entirely across the repellent band were considered repelled. For all formulations and time points, significantly fewer (all P <0.0001) A. americanum nymphs crossed the treatment bands on the volunteers’ ankles than crossed the corresponding area on the untreated control legs. Formulations containing =20% active ingredient were highly effective, with <10% of the ticks crossing through the treatment bands for any challenge during the 12 h. At least 40% of ticks exposed to any formulation for any challenge fell or crawled from the volunteers. There was no difference in effectiveness between the 20% spray and 20% lotion formulations of picaridin. The 10% IR3535 lotion was significantly less effective than the formulations with higher concentrations of repellent.