Arm-in-cage testing of natural human-derived mosquito repellents
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Date
2010
Authors
James, Logan G.
Nina, Stanczyk M.
Hassanali, Ahmed
Kemei, Joshua
Santana, Antônio E.G.
Karlos, Ribeiro A.L.
John, Pickett A.
Mordue, Jennifer A.
Journal Title
Journal ISSN
Volume Title
Publisher
Biomed Central
Abstract
Background: Individual human subjects are differentially attractive to mosquitoes and other biting insects.
Previous investigations have demonstrated that this can be attributed partly to enhanced production of natural
repellent chemicals by those individuals that attract few mosquitoes in the laboratory. The most important
compounds in this respect include three aldehydes, octanal, nonanal and decanal, and two ketones, 6-methyl-5-
hepten-2-one and geranylacetone [(E)-6,10-dimethylundeca-5,9-dien-2-one]. In olfactometer trials, these compounds
interfered with attraction of mosquitoes to a host and consequently show promise as novel mosquito repellents.
Methods: To test whether these chemicals could provide protection against mosquitoes, laboratory repellency
trials were carried out to test the chemicals individually at different concentrations and in different mixtures and
ratios with three major disease vectors: Anopheles gambiae, Culex quinquefasciatus and Aedes aegypti.
Results: Up to 100% repellency was achieved depending on the type of repellent compound tested, the
concentration and the relative composition of the mixture. The greatest effect was observed by mixing together
two compounds, 6-methyl-5-hepten-2-one and geranylacetone in a 1:1 ratio. This mixture exceeded the repellency
of DEET when presented at low concentrations. The repellent effect of this mixture was maintained over several
hours. Altering the ratio of these compounds significantly affected the behavioural response of the mosquitoes,
providing evidence for the ability of mosquitoes to detect and respond to specific mixtures and ratios of natural
repellent compounds that are associated with host location.
Conclusion: The optimum mixture of 6-methyl-5-hepten-2-one and geranylacetone was a 1:1 ratio and this
provided the most effective protection against all species of mosquito tested. With further improvements in
formulation, selected blends of these compounds have the potential to be exploited and developed as humanderived
novel repellents for personal protection.
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Citation
Malaria Journal 2010, 9:239