ARS | Publication request: Twelve-hour duration testing of cream formulations of three repellents against Amblyomma americanum (Acari: Ixodidae)

Submitted to: Medical and Veterinary Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 1, 2007
Publication Date: June 1, 2008
Citation: Carroll, J.F., Benante, J.P., Klun, J.A., White, C., Debboun, M., Pound, J.M., Dheranetra, W. 2008. Twelve-hour duration testing of cream formulations of three repellents against Amblyomma americanum (Acari: Ixodidae). Medical and Veterinary Entomology. 22:144-151.

Interpretive Summary: Ticks are vectors of a variety of bacterial, viral and protozoan pathogens capable of causing debilitating and sometimes fatal illnesses in humans. Repellents are a last line of personal protection from tick bite. An important measure of a repellent’s effectiveness is the duration of its repellency after application. The Department of Defense sought a comparison of the standard military repellent against promising newer repellents in cream formulations. We evaluated 10 and 20% Bayrepel, 10 and 20% SS220, 33% deet (standard military repellent) creams and an untreated control in a simulated field test. A band of repellent was applied (encircling) to each lower leg of human volunteers (under approved Walter Reed Army Institute of Research Human Volunteer Protocol) and challenged by exposure to host-seeking lone star tick nymphs at 2-h intervals for 12 h. Ticks crawled upward from feet of volunteers. All repellents were highly effective for 12 h. No ticks crossed the bands of 20% Bayrepel and 20% SS220 during any challenge, thus providing 100% protection throughout the test.

Technical Abstract: The repellent efficacy of the United States military repellent 33% N,N-diethyl-3-methylbenzamide (deet), 10 and 20% (1S, 2'S) 2-methylpiperidinyl-3-cyclohexene-1-carboxamide (SS220) and 10 and 20% 1-methyl-propyl-2-(hydroxyethyl)-1-piperidinecarboxylate (Bayrepel) cream formulations on human volunteers was evaluated against lone star ticks, Amblyomma americanum, in a simulated forest floor environment over a 12-h duration testing period. At 2-h intervals, volunteers with repellent applied in a 5-cm wide band encircling each lower leg, stood for 10 min in plastic tubs containing leaf litter and 100 host-seeking A. americanum nymphs. All formulations provided highly significant protection for the entire 12 h. No ticks crossed the 5-cm wide bands of 20% Bayrepel and SS220 during any challenge, thus providing 100% protection throughout the test.