BEHAVIOR, CHEMICAL ECOLOGY Repellent and Deterrent Effects of SS220, Picaridin, and Deet Suppress Human Blood Feeding by Aedes aegypti, Anopheles stephensi, and Phlebotomus papatasi

A series of behavioral tests with Aedes aegypti (L.), Anopheles stephensi Liston, mosquitoes, and the sand ßy Phlebotomus papatasi Scopoli in the presence of Deet, SS220, and Picaridin topically applied to the skin of human volunteers showed that the insects were deterred from feeding on and repelled from surfaces emanating the compounds. When offered a 12or 24-cm area of skin, one-half treated with compound and one-half untreated, the insects fed almost exclusively on untreated skin. The sandßies andmosquitoes did not at any timephysically contact chemically treated surfaces. When treated and untreated skin areas were covered with cloth, insects contacted, landed, and bit only through cloth covering untreated skin. These observations provided evidence that the compounds deterred feeding and repelled insects from treated surfaces primarily as a result of olfactory sensing.Whencloth, one-half untreated andone-half treatedwith chemical,was placedover untreated skin, insects only touched and speciÞcally bit through the untreated cloth. This showed that the activity of the chemicals does not involve a chemical skin interaction. In the presence of any of the three chemicals, no matter how they were presented to the insects, overall population biting activity was reduced by about one-half relative to controls. This reduction showed a true repellent effect for the compounds. Results clearly showed that Deet, SS220, and Picaridin exert repellent and deterrent effects upon thebehavior ofmosquitoes and sandßies.Heretofore, the combinedbehavioral effectsof thesecompoundsuponmosquitoandsandßybehaviorwereunknown.Moreover,protection afforded by Deet, SS220, and Picaridin against the feeding of these three disease vectors on humans is mechanistically a consequence of the two chemical effects.