Abstract:
BACKGROUND: Methods currently used in sampling adult Aedes aegypti, the main vector of dengue and chikungunya
viruses are limited for effective surveillance of the vector and accurate determination of the extent of virus
transmission during outbreaks and inter - epidemic periods. Here, we document the use of natural human skin
odours in baited traps to improve sampling of adult Ae. aegypti in two different endemic areas of chikungunya and
dengue in Kenya – Kilifi and Busia Counties. The chemistry of the volatiles released from human odours and the
Biogent (BG)-commercial lure were also compared.
METHODS: Cotton socks and T-shirts were used to obtain natural human skin volatiles from the feet and trunk of three
volunteers (volunteers 1 and 2 in Kilifi and volunteers 2 and 3 in Busia). Using Latin square design, we compared
the efficacies of BG sentinel traps baited with carbon dioxide plus (a) no bait, (b) human feet volatiles, (c) human
trunk volatiles each against (c) a control (Biogent commercial lure) at the two sites. Coupled gas chromatography-mass
spectrometry (GC-MS) was used to identify and compare candidate attractants released by the commercial lure and
human odours.
RESULTS: Ae. aegypti captured in the trap baited with feet odours from volunteer 2 and trunk odours from the same
volunteer were significantly higher than in the control trap in Busia and Kilifi respectively, [IRR = 5.63, 95% CI: 1.15 - 28.30,
p = 0.030] and [IRR = 3.99, 95% CI: 0.95-16.69, p = 0.049]. At both sites, Ae. aegypti captures in traps baited with either the
feet or trunk odours from volunteers 1 and 3 were not significantly different from the control. Major qualitative
differences were observed between the chemical profiles of human odours and the commercial BG-lure. Aldehydes,
fatty acids and ketones dominated human odour profiles, whereas the BG-lure released mainly hexanoic acid.
CONCLUSIONS: Our results suggest that additional candidate attractants are present in human skin volatiles which can
help to improve the efficacy of lures for trapping and surveillance of Ae. aegypti.
