UBC Theses and Dissertations
Applying concepts of surface engineering in the development of anti-mosquito surfaces Recla, Letícia
Mosquito-borne diseases such as malaria remain a heavy burden on society. In its latest annual report, the World Health Organization (WHO) estimated that 228 million people contracted malaria in 2018. Increasing drug resistance among mosquito populations and the growing public concern about the use of synthetic chemistries have encouraged researchers to develop new mosquito deterrents. Recent studies have suggested that sub-lethal doses of natural repellents could reduce drug resistance by decreasing the pressure for natural selection. Natural selection can also be reduced by using physical deterrents instead of toxic repellents. In this work, we use a modified high-throughput screening system to evaluate the repellent properties of a rotundial-containing paint additive against Aedes aegypti females in spatial repellency and contact irritancy assays. Rotundial is a dialdehyde naturally occurring in the leaves of Vitex rotundifolia and previously reported to exhibit mosquito-repellent properties. Our results showed however, that rotundial is an unstable molecule that will undergo biodegradation within days to weeks after extraction, even in the absence of oxygen, making it unsuitable for long-lasting applications. In this work we also studied the ability of Aedes aegypti mosquitoes to land and sustain themselves on vertical surfaces. We exposed glass samples of varying roughness to a live mosquito colony and concluded that mosquitoes were unable to land on glass samples with an average Sq roughness below 0.143 µm. Surface interactions such as Van der Waals and capillary forces contribute to adhesion after a successful grip has been achieved, but cannot alone promote stable vertical landing on smooth surfaces. This roughness threshold for Aedes aegypti was shown to be independent of relative humidity, colony age, and surface energy, but could vary between mosquito species. To our knowledge, this is the first study to understand the effects of various surface characteristics on the adhesion of live mosquitoes.
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