Abstract
Host-derived repellents offer a novel way to reduce disease vector–host interactions, particularly for vectors and nuisance pests where commercial repellents are not available, e.g., Culicoides biting midges. By revising the criteria previously used to identify bioactive volatile organic compounds for Culicoides nubeculosus, we identify (E)-2-hexenal, (E)-2-heptenal, (E)-2-octenal, and (E)-2-nonenal to be differentially present in the headspace odour of cattle hair and to elicit antennal responses in this research model species. A blend of these unsaturated aldehydes elicited an aversive response in C. nubeculosus, as well as a repellent response in three disease vector mosquito species, Aedes aegypti, Culex quinquefasciatus and Anopheles coluzzii, a response that was stronger than that to the commercially available repellents tested (DEET, IR3535, PMD, icaridin, and d-allethrin). Culicoides nubeculosus was behaviourally indifferent to these commercially available repellents tested, except d-allethrin to which it was attracted. The identification of a host-derived repellent odour blend, which reduces the interaction between biting midges extends the array of tools to be used in integrated vector management of these and other disease vectors.
Highlights
The biting habit of Culicoides biting midges has a dire effect on animal and human welfare, at a global scale
We identify a blend of four unsaturated aldehydes that deter Culicoides biting midges and mosquitoes in laboratory and field experiments
3-octen-2-one and four unidentified monoterpenes fulfilled the criteria as bioactive compounds using the revised criteria, but were not included in further analysis. 3-Octen-2-one was not considered for further analysis, as we were interested in elucidating the repellent properties of the unsaturated aldehydes, especially as previous field experiments demonstrated that (E)-2-nonenal repelled biting midges (Isberg et al 2017)
Summary
The biting habit of Culicoides biting midges has a dire effect on animal and human welfare, at a global scale. Non-host volatiles (NHVs) and host-derived repellents, both emanating from potential vertebrate blood hosts, have been demonstrated to deter disease-transmitting insects, including tsetse (Gikonyo et al 2002; Gikonyo et al 2003) and cattle flies (Birkett et al 2004), as well as mosquitoes (Jaleta et al 2016) under field conditions. Non-host volatiles and host-derived repellents are likely indicators of nutritionally, or otherwise, unsuitable hosts (Lyimo and Ferguson 2009). While these deterrents may be species-specific, there are ample examples, not least from herbivorous insects (Cook et al 2007),
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