Field evaluation of the efficacy and persistence of insect repellents DEET, IR3535, and KBR 3023 against Anopheles gambiae complex and other Afrotropical vector mosquitoes

Abstract

Synthetic insect repellents, IR3535 and KBR 3023 (also known as picaridin, or by the trade name Bayrepel ®), were tested in Burkina Faso against mosquito vectors of disease to compare their relative efficacy and persistence profiles to those of the ‘gold standard’ DEET. Collection of >49 000 mosquitoes (∼95% belonging to the Anopheles gambiae complex) showed that after an exposure of 10 h, KBR 3023 produced the highest protection against anophelines, followed by DEET, then IR3535. The response of aedines was more variable. By fitting a logistic plane model we estimated 95% effective dosages (ED 95) for An. gambiae s.l., as well as a decay constant characterizing the exponential loss of repellent from the skin, with time. The ED 95 values for DEET, IR3535, and KBR 3023 were 94.3, 212.4, and 81.8 μg/cm 2 respectively. The decay constants were estimated at −0.241, −0.240, and −0.170 h −1 respectively. The corresponding estimates of half-life were 2.9, 2.9, and 4.1 h. Immunoenzymatic detection of the circumsporozoite protein (CSP) of Plasmodium falciparum in 842 An. gambiae s.l. showed that CSP-positive mosquitoes were equally frequent in treated and control subjects, indicating that the repellents could produce a reduction in the number of malaria infectious bites.