Abstract
Vector-borne diseases are worldwide public health issues. Despite research focused on vectorial capacity determinants in pathogen transmitting mosquitoes, their behavioural plasticity remains poorly understood. Memory and associative learning have been linked to behavioural changes in several insect species, but their relevance in behavioural responses to pesticide vector control has been largely overlooked. In this study, female Aedes aegypti and Culex quinquefasciastus were exposed to sub-lethal doses of 5 pesticide compounds using modified World Health Organization (WHO) tube bioassays. Conditioned females, subsequently exposed to the same pesticides in WHO tunnel assays, exhibited behavioural avoidance by forgoing blood-feeding to ensure survival. Standardized resting site choice tests showed that pre-exposed females avoided the pesticides smell and choose to rest in a pesticide-free compartment. These results showed that, following a single exposure, mosquitoes can associate the olfactory stimulus of pesticides with their detrimental effects and subsequently avoid pesticide contact. Findings highlight the importance of mosquito cognition as determinants of pesticide resistance in mosquito populations targeted by chemical control.
Highlights
Vector-borne diseases are worldwide public health issues
In Ae. aegypti 69.1% and 77.2% of Cx. quinquefasciatus females that were non-pre-exposed to pesticides fed successfully on the host when faced with an untreated net (Fig. 1a, b)
This study provides the first comprehensive experimental evidence of learned pesticide avoidance in females of two major vector species, Ae. aegypti and Cx. quinquefasciatus
Summary
Vector-borne diseases are worldwide public health issues. Despite research focused on vectorial capacity determinants in pathogen transmitting mosquitoes, their behavioural plasticity remains poorly understood. The most important mosquito vectors are Anopheles, Aedes and Culex species that feed preferentially on humans inside and around their dwellings In such setting, chemical vector control measures in the form of insecticide treated bed nets (ITNs), indoor residual spraying (IRS) and outdoor space spraying have proved the most effective in reducing mosquito populations and disease transmission[14]. Behavioural avoidance or ’deterrence’ is another mechanism of resistance described as the innate ability of mosquitoes to decrease insecticide exposure by moving away from treated areas[26,27] This response to insecticides is referred to as ’irritancy’, and is elicited following physical contact with a pesticide treated surfaces whereas ’repellency’ occurs without c ontact[28,29]
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