GC/EAD profiles of headspace volatiles collected from natural host plants of specific Afro-tropical mosquitoes.

A) Aedes aegypti gambiae antennal detection of specific VOCs from Pithecellobium dulce.B) Aedes mcintoshi antennal detection of VOCs from Opuntia ficus-indica. C) Anopheles gambiae antennal detection of specific VOCs from Leonotis nepetifolia. D) An. gambiae antennal detection of specific VOCs from Senna alata.</p

Heat map showing varying intensities of antennal responses to synthetic standards of identified compounds in three mosquito species.

<p>The heat maps are based on doses (4ng/μl) of each compound eliciting the highest antennal responses in the respective mosquito species. Green represent higher responses while red indicate lower responses. White asterisks denote significant differences between two mosquito species. Differences in antennal responses were detected using ANOVA and the means separated with Tukey post hoc test.</p

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

<div><p>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 <i>Aedes aegypti</i> (dengue), two for both <i>Aedes mcintoshi</i> and <i>Aedes ochraceus</i> (Rift Valley fever) and five for <i>Anopheles gambiae</i> (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 <i>Ae</i>. <i>aegypti</i>, <i>Ae</i>. <i>mcintoshi</i> and <i>An</i>. <i>gambiae</i> from their respective host plants. Whereas <i>Ae</i>. <i>aegypti</i> predominantly detected benzenoids, <i>Ae</i>. <i>mcintoshi</i> detected mainly aldehydes while <i>An</i>. <i>gambiae</i> detected sesquiterpenes and alkenes. Interestingly, the monoterpenes β-myrcene and (<i>E</i>)-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.</p></div

Concentration (pg/mg) of cholesterol metabolites in various tissues after incubation with normal cholesterol (C) and labeled Cholesterol-[4-¹³C] (C-[4-¹³C]).

<p>Retention time (R_t), foregut (FG), midgut (MG) and hindgut (HG).</p><p>^○ Identified by comparison with authentic samples.</p><p>^◊ Identification by search in the spectra database and through derivatization.</p><p>✘ denotes not detected.</p><p>Concentration (pg/mg) of cholesterol metabolites in various tissues after incubation with normal cholesterol (C) and labeled Cholesterol-[4-¹³C] (C-[4-¹³C]).</p

Forward and reverse primer sequences for three gene targets used to identify natural host plants of dengue, Rift Valley fever and malaria mosquito disease vectors.

<p>Forward and reverse primer sequences for three gene targets used to identify natural host plants of dengue, Rift Valley fever and malaria mosquito disease vectors.</p

Variable success rates of two gene targets in amplifying and sequencing plant DNA in the crop of different mosquito species.

<p>Variable success rates of two gene targets in amplifying and sequencing plant DNA in the crop of different mosquito species.</p

Electroantennographic detection responses of three Afro-tropical mosquito species to different doses of commonly detected plant volatile organic compounds.

<p>Variability in EAG responses were corrected by subtracting the responses to blanks (5 μl dichloromethane and bioassay filter paper) from each sample and the antennal response values normalized to a standard stimulus set at 100% (2 ng/μl 1-octen-3-ol). Bars capped with different letters are significantly different between the three doses. The differences in dose response were detected using ANOVA followed by Tukey post hoc test.</p

NJ phylogenetic trees from two gene targets showing plant species identified as natural host plants of the Afro-tropical mosquito species.

<p>A) Plant species identified using trnH-psbA gene targets as host plants for <i>Aedes aegypti</i>, <i>Aedes mcintoshi</i>, <i>Aedes ochraceus</i> and <i>Anopheles gambiae</i>. B) Plant species identified using matK gene targets as host plants for <i>Anopheles gambiae</i>. Plant species names with prefix Aa from <i>Aedes aegypti</i>, Am from <i>Aedes mcintoshi</i>, Ao from <i>Aedes ochraceus</i> and Ag represent those that were identified from <i>Anopheles gambiae</i>, the numbers being sample ID. Plant species with prefix P1-4 represent the plant samples sequences to confirm the identity of the mosquito host plants while those with suffixes are outgroups from GenBank with extension being accession numbers.</p

Biodiversity estimators of <i>Aedes mcintoshi</i> and <i>Aedes ochraceus</i> microbiota (mean ± standard error).

Biodiversity estimators of Aedes mcintoshi and Aedes ochraceus microbiota (mean ± standard error).</p

Nonmetric Multidimensional Scaling (NMDS) ordination displaying the microbial communities of <i>Aedes mcintoshi</i> and <i>Aedes ochraceus</i>.

(a) both species from all sites pooled, (b) both species by study site, (c) Ae. ochraceus by study site and (d) Ae. mcintoshi by study site.</p