Host plant forensics and olfactory-based detection in Afro-tropical mosquito disease vectors

Abstract

The global spread of vector-borne diseases remains a worrying public health threat, raising the need for development of new combat strategies for vector control. Knowledge of vector ecology can be exploited in this regard, including plant feeding; a critical resource that mosquitoes of both sexes rely on for survival and other metabolic processes. However, the identity of plant species mosquitoes feed on in nature remains largely unknown. By testing the hypothesis about selectivity in plant feeding, we employed a DNA-based approach targeting trnH-psbA and matK genes and identified host plants of field-collected Afro-tropical mosquito vectors of dengue, Rift Valley fever and malaria being among the most important mosquito-borne diseases in East Africa. These included three plant species for Aedes aegypti (dengue), two for both Aedes mcintoshi and Aedes ochraceus (Rift Valley fever) and five for Anopheles gambiae (malaria). Since plant feeding is mediated by olfactory cues, we further sought to identify specific odor signatures that may modulate host plant location. Using coupled gas chromatography (GC)-electroantennographic detection, GC/mass spectrometry and electroantennogram analyses, we identified a total of 21 antennally-active components variably detected by Ae. aegypti, Ae. mcintoshi and An. gambiae from their respective host plants. Whereas Ae. aegypti predominantly detected benzenoids, Ae. mcintoshi detected mainly aldehydes while An. gambiae detected sesquiterpenes and alkenes. Interestingly, the monoterpenes β-myrcene and (E)-β-ocimene were consistently detected by all the mosquito species and present in all the identified host plants, suggesting that they may serve as signature cues in plant location. This study highlights the utility of molecular approaches in identifying specific vector-plant associations, which can be exploited in maximizing control strategies such as such as attractive toxic sugar bait and odor-bait technology.

Innovative approaches to exploit host plant metabolites in malaria control

“…Since plants are the major sources of sugar feeding in mosquitoes, it is important to know precisely the plants used for this behavioral trait by mosquitoes. During sugar feeding, mosquitoes ingest minute amounts of plant tissue . The reason for mosquitoes ingesting plant tissue needs further exploration.…”

“…The first report of plants fed upon by wild‐caught An. gambiae based on DNA barcoding was by Nyasembe et al . Several plant species were identified from a malaria endemic area in Kenya, including Senna alata and Senna tora (Fabaceae), Ricinus communis (Euphorbiaceae), Parthenium hysterophorus and Leonotis nepetifolia (Lamiaceae).…”

“…The first report of plants fed upon by wild-caught An. gambiae based on DNA barcoding was by Nyasembe et al 29 Several plant species were identified from a malaria endemic area in Kenya, including Senna alata and Senna tora (Fabaceae), Ricinus communis (Euphorbiaceae), Parthenium hysterophorus and Leonotis nepetifolia (Lamiaceae). Additionally, research has shown that use of sensitive chemical techniques such as gas chromatography linked to electroantennographic detection (GC-EAD) can allow for isolation of headspace volatile components detected by antennae of An.…”

“…During sugar feeding, mosquitoes ingest minute amounts of plant tissue. 29 The reason for mosquitoes ingesting plant tissue needs further exploration. To identify the Pest Manag Sci 2019; 75: 2341-2345…”

Indolergic receptors of the elephant mosquitoToxorhynchites amboinensis

“…gambiae (Blackwell and Or9. The functional conservation of these receptors across the two mosquito subfamilies in both sexes and in 48 larvae suggest that indole and skatole play important and multiple roles in the biology of these insects ( Figure 49 1A) (Cork, 1996;Nyasembe et al, 2018). 50…”