Understanding the role of local vegetation in mosquito feeding behaviour
Looking at the role of plant nectar
Mosquitoes, both males and females, feed on nectar for their daily energy requirements. They can detect a nectar source using visual olfactory and/or gustatory cues, but there is limited knowledge about how these are perceived by mosquitoes and the mechanisms involved. Mosquito nectar feeding behaviour and the need for new methods of control due to insecticide resistance have fostered the development of new mosquito control methods such as Attractive Toxic Sugar Baits (ATSBs). These baits contain sugar from flowers and fruits to attract mosquitoes, and a toxic compound to kill them. However, sites with high levels of nectar sugar and/or plants attractive to mosquitoes might significantly lower their efficacy.
My research aims to better understand the role of local vegetation in mosquito feeding behaviour, focusing on Anopheles gambiae. This species is one of the most efficient and well-studied vectors of malaria in the world, responsible for the high level of transmission across much of sub-Saharan Africa. Studies have investigated the feeding behaviour and survival rates of An. gambiae using different African plants and have shown that An. gambiae prefers specific species of plants under controlled experiments. However, more studies are needed to better understand An. gambiae feeding behaviour in the field.
To address the above gaps, my research aims to answer the following questions:
Do mosquitoes show preferences for particular plant nectar? If so, which plant nectar do they prefer to feed on?
To address this question, I conducted a systematic review that encompassed peer-reviewed published literature and grey literature. Following best practice guidelines from the "Collaboration for Environmental Evidence," an interactive map was created where users can analyse the results based on selected criteria. Data extracted from the review process were analysed to identify studies with high and low risk of bias and to determine if mosquitoes preferred to feed on particular plants, focusing only on low risk of bias studies.
Do changes in vegetation over time (seasonality) and space (abundance) affect the efficacy of ATSBs?
Collaborating with the Innovative Vector Control Consortium, we aim to develop a model to calculate the amount of sugar available at study sites to better understand the impact of local vegetation on ATSB efficacy. To achieve this, we will conduct vegetation surveys at the study sites and select the most abundant and attractive plants identified in the systematic review. Subsequently, we will collect various plant traits for each selected plant species, including i) number of flowers per individual plant, ii) nectar volume, iii) sugar concentration in nectar, and iv) phenology. By combining this information with remote sensing images, we will estimate the nectar resource at the study site in both space and time. Clusters will be classified as high or low sugar nectar areas based on the estimated sugar content in each cluster. Our objective is to compare and contrast the numbers of mosquitoes feeding on ATSBs in different landscape types (high and low sugar nectar sites). We anticipate that ATSBs deployed in areas with higher levels of available plant sugar nectar will exhibit poorer performance than those in areas with lower levels of available plant nectar. Such information may prove critical for the success of ATSBs in local mosquito control interventions.
How do mosquitoes identify their preferred nectar?
Mosquitoes locate their favourite plants using olfactory, visual, and gustatory cues. Recent studies have also shown, however, that it is likely a combination of visual, olfactory, and CO2 emissions by the plant that enhances this attraction. The role of CO2 in mosquito attraction to humans and other animals is well known, but more studies are needed to better understand its role in mosquito and plant interactions. It has been suggested that blood feeding by mosquitoes may have evolved from a phytophagy diet. CO2 and other common odorants shared by animals and plants may have facilitated the transition from plants to vertebrate hosts. We will study the importance of this gas in mosquito-flower attraction by selecting attractive and non-attractive plants to An. gambiae and measuring CO2 emitted by the flowers.
