Malaria incidence in urban areas has generally been low compared to rural areas but recent data indicate that urban malaria remains a public health problem. It is therefore important to understand the factors that pro...Malaria incidence in urban areas has generally been low compared to rural areas but recent data indicate that urban malaria remains a public health problem. It is therefore important to understand the factors that promote urban malaria to help formulate future vector control strategies. This study compared Anopheles gambiae s.l. (A. gambiae s.l.) species composition, distribution and insecticide resistance mechanisms between vegetable and non-vegetable growing areas in Accra Metropolis. Four sites were selected within the city of Accra which comprised of two vegetable-growing and two non-vegetable growing areas. WHO susceptibility tests were carried out on adults A. gambiae s.l. reared from larvae collected from the sites. Five insecticides were tested and the A. gambiae complex, resistance genotypes and enzyme activities of each population were characterized. All A. gambiae s.l. populations tested were resistant to all the insecticides, but relatively lower mortalities were observed in the vegetable growing areas. The mortality against 0.05% deltamethrin was 2.6% (Opeibea) and 12.5% (Korle-Bu) for the vegetable growing areas and 36.2% (Achimota) and 38.9% (Mataheko) in the non-vegetable growing areas. Anopheles gambiae s.s. (95% of Opeibea population) and Anopheles coluzzii, (98% of Korle-Bu population) were the dominant species in the vegetable growing areas. The voltage-gated sodium channel (Vgsc-1014F) frequencies of all the populations were similar but the acetylcholinesterase (ace-1) frequencies were significantly lower (p A. gambiae s.l. from Opeibea than from the other areas. The contribution of urban agriculture in the development of insecticide resistance needs to be considered in the formulation of future vector control strategies alongside other domestic usages.展开更多
Objective:To evaluate the larvicidal efficacy of eight volatile components of essential oils against 3rd instar larvae of Anopheles gambiae s.s.Methods:Larvicidal effects of each compound were evaluated in both labora...Objective:To evaluate the larvicidal efficacy of eight volatile components of essential oils against 3rd instar larvae of Anopheles gambiae s.s.Methods:Larvicidal effects of each compound were evaluated in both laboratory and semi-field trials.Stock solution was prepared and serial dilutions were made in six concentrations for each compound.A total of 20 larvae were exposed to larvicides for each replicate and monitored at intervals of 12,24,48 and 72 h.Larvae monitoring was done on basis of dead and live larvae in all intervals.Results:All assayed compounds were larvicides and presented varying degrees of larval toxicity,with LC_(50)values ranging from 1.28 to 1938.92 mg/L depending on the treatment time(12,24,48 or 72 h).(-)-Perillyl alcohol presented the strongest larvicidal activity towards Anopheles gambiae larvae,with LC_(50)values of 73.60,18.36,1.72 and1.28 mg/L after 12,24,48 and 72 h of exposure,respectively.The next strongest were(-)-isopulegol(LC_(50)=135.10,49.39,34.39 and 20.22 mg/L)and(-)-carvone epoxide(LC_(50)=168.86,124.74,80.84 and 23.46 mg/L).After 12,24 and 48 h of treatment,hydroxydihydrocarvone was the least toxic compound,with LC_(50)values of 1938.92,1172.18 and 401.03 mg/L,respectively.Conclusions:The data obtained in this study suggest that all evaluated monoterpenes,especially(-)-perillyl alcohol,have remarkable larvicidal effects and may be considered as potential sources for the development of suitable natural larvicides for mosquito management programs.Further small-scale field trials should be conducted.展开更多
Objective:To screen phytochemicals in ethanolic leaf extracts of Phyllanthus amarus collected from three different geographical zones in Nigeria and evaluate their effects on larva and adult of Anopheles gambiae.Metho...Objective:To screen phytochemicals in ethanolic leaf extracts of Phyllanthus amarus collected from three different geographical zones in Nigeria and evaluate their effects on larva and adult of Anopheles gambiae.Methods:The sample extracts of Phyllanthus amarus prepared with ethanol solvent were tested against Anopheles gambiae at two important developmental stages of its life cycle using slightly modified WHO protocols.Results:Alkaloids,saponins,tannins,flavonoids,glycosides,phenols,and terpenes were detected in each extract.Among these samples,the extract from northwest exhibited the highest larvicidal activity(LC50=263.02 ppm),followed by southeast and southwest extracts(LC50=288.40 and 295.12 ppm,respectively after 48 h),while the extract from southwest exhibited the highest adulticidal activity(LC50=275.42 ppm),followed by northwest and southeast extract(LC50=301.99 and 316.22 ppm,respectively after 24 h).A 50%larva mortality was almost attained at 600 ppm after 48 h duration of exposure to the northwest extract.Conclusions:The tested samples possess strong larvicidal and adulticidal property against Anopheles gambiae which depends on their chemical composition and localities of collection.Further studies are needed to explore the insecticidal activity against a wider range of mosquito species,and to identify active ingredient(s)of the extract responsible for such activity.展开更多
Understanding the genetic architecture of indi-vidual taxa of medical importance is the first step for designing disease preventive strategies. To understand the genetic details and evolu-tionary perspective of the mo...Understanding the genetic architecture of indi-vidual taxa of medical importance is the first step for designing disease preventive strategies. To understand the genetic details and evolu-tionary perspective of the model malaria vector, Anopheles gambiae and to use the information in other species of local importance, we scanned the published X-chromosome se-quence for detail characterization and obtain evolutionary status of different genes. The te-locentric X-chromosome contains 106 genes of known functions and 982 novel genes. Majori-ties of both the known and novel genes are with introns. The known genes are strictly biased towards less number of introns;about half of the total known genes have only one or two in-trons. The extreme sized (either long or short) genes were found to be most prevalent (58% short and 23% large). Statistically significant positive correlations between gene length and intron length as well as with intron number and intron length were obtained signifying the role of introns in contributing to the overall size of the known genes of X-chromosome in An. gam-biae. We compared each individual gene of An. gambiae with 33 other taxa having whole ge-nome sequence information. In general, the mosquito Aedes aegypti was found to be ge-netically closest and the yeast Saccharomyces cerevisiae as most distant taxa to An. gambiae. Further, only about a quarter of the known genes of X-chromosome were unique to An. gambiae and majorities have orthologs in dif-ferent taxa. A phylogenetic tree was constructed based on a single gene found to be highly orthologous across all the 34 taxa. Evolutionary relationships among 13 different taxa were in-ferred which corroborate the previous and pre-sent findings on genetic relationships across various taxa.展开更多
The progress in the field of nanotechnology has contributed to the development of tools for combating the most critical problems in developing countries. The requirements that such tools should meet are low-cost and r...The progress in the field of nanotechnology has contributed to the development of tools for combating the most critical problems in developing countries. The requirements that such tools should meet are low-cost and resource settings, environmental protection, ease of use, and availability. The use of plant properties for the generation of nanoparticles (NPs), which serve as bioinsecticides to combat the plasticity and resistance of mosquitoes and parasites, is considered possible. Here, we report for the first time the larvicidal activity of silver (Ag) NPs (AgNPs) synthesized from Psidium guajava (P. guajava) extract, which targets the 4th instar larvae of Anopheles gambiae. Concentrations of AgNPs between 0 and 200 ppm were used and their LC50 at 24 h and 48 h were determined as 19.55 ppm and 8.737 ppm, respectively. The AgNPs were stable and highly effective against the larvae of A. gambiae and thereby we anticipate that they can be used to combat vector-borne diseases in developing countries.展开更多
The epsilon class glutathione-S-transferase of Anopheles gambiae, agGSTe2, is capable of metabolizing DDT. A molecular docking analysis of DDT with agGSTe2 support an E2 elimination mechanism wherein the glutathione s...The epsilon class glutathione-S-transferase of Anopheles gambiae, agGSTe2, is capable of metabolizing DDT. A molecular docking analysis of DDT with agGSTe2 support an E2 elimination mechanism wherein the glutathione sulfur serves as the base to convert DDT to DDE.展开更多
Background: Mosquitoes are responsible of numerous vector-borne diseases and among these diseases is malaria which takes away lives of thousands of people, especially children of under five, particularly in Africa. To...Background: Mosquitoes are responsible of numerous vector-borne diseases and among these diseases is malaria which takes away lives of thousands of people, especially children of under five, particularly in Africa. To reduce the mortality and economic burdens of this deadly disease, synthetic insecticide has been of use to control its main vector, Anopheles gambiae. Due to adverse effects caused by these conventional products on non-target organisms and the environment, plants have been of first choice as they proved their effectiveness against mosquitoes and are said to be eco-friendly and relatively safer. Therefore, the aim of this study was to screen the phytochemicals and determine the larvicidal and adult emergence exhibitory activities of Momordica charantia and Hyptis spicigera leaves extracts against Anopheles gambiae larvae. Methods: The WHO standard protocol for larvicidal activity and IGRs was followed up and concentrations from 500 - 2000 ppm for larvicidal and 500 - 1500 ppm for IGRs were set up. Results: There was the presence of alkaloids, flavonoids, tannins, phenols, steroids, terpenoids and oils in Momordica charantia against alkaloids, taponins, tannins, phenols, steroids, terpenoids and oils in Hyptis spicigera. Methanol crude extract registered the lowest LC<sub>50</sub> value of 270.6 ppm followed by ethyl acetate and hexane fractions recorded the LC<sub>50</sub> of 742.1 and 756 ppm, respectively for larvicidal activity of Momordica charantia against LC<sub>50</sub> of 760 and 867.5 ppm for hexane fraction and methanol crude extract, respectively for Hyptis spicigera. Methanol crude extract and hexane fraction of both plants as well as the ethyl acetate fraction of M. charantia registered greater emergence inhibition with IE<sub>50</sub> values of 590.2, 842.3 and 982 ppm for methanol crude extract, hexane and ethyl acetate fractions of M. charantia, respectively against 901.7 and 873.2 for methanol crude extract and hexane fraction of H. spicigera, respectively. Conclusion: The toxicity and adult emergence inhibition may be associated with constituents in both plants that interfere with the normal neuronal, respiratory and endocrine systems functions.展开更多
Background: Anopheles gambiae is enemy number one of mankind in Africa and particularly in Cameroon due to its ability of transmitting malaria which is the deadliest disease in this part of the world. Synthetic insect...Background: Anopheles gambiae is enemy number one of mankind in Africa and particularly in Cameroon due to its ability of transmitting malaria which is the deadliest disease in this part of the world. Synthetic insecticides have been used to control malaria vectors but they have negative effects on non-target organisms and are environmentally unfriendly. Control of mosquitoes at larval stages using phytochemicals is currently the leading tool to reduce the mosquito population and so the reduction of malaria transmission rates. Therefore, the present study was to evaluate the phytochemical contents, larvicidal and adult emergence inhibition activities of Balanites aegyptiaca seed and Aristolochia albida root solvents extracts against Anopheles gambiae larvae. Methods: The World Health Organization standard protocols were followed for the different bioassays. Concentrations ranging from 500 - 2000 ppm for larvicidal and 500 - 1500 ppm for IGRs were used. Results: Both plants showed the presence of alkaloids, flavonoids, saponins, tannins, phenols, terpenoids and oils except the absence of phenols in Aristolochia albida. The larvicidal activity of Aristolochia albida extracts showed that hexane and methanol fractions were the most active killing relatively all exposed larvae with the LC<sub>50</sub> values of 420.1 and 453 ppm, respectively. The same observation was made in hexane fraction from Balanites aegyptiaca (LC<sub>50</sub> = 588 ppm). The insect growth inhibitory activity of Aristolochia albida extracts proved that hexane and methanol fractions relatively caused a 100% inhibition in the mosquito development, recording the EI<sub>50</sub> values of 482.4 and 555.6 ppm, respectively. The same trend was observed with Balanites aegyptiaca hexane fraction registering better EI<sub>50</sub> of 623.9 ppm. Conclusions: Our findings demonstrate that Balanites aegyptiaca seed and Aristolochia albida seed extracts are rich in phytochemicals capable of killing mosquito larvae and disrupting mosquito larval development. This could contribute to the control of mosquito populations and improved management of malaria.展开更多
<strong>Background: </strong><span><span><span><span>With the rapid expansion of insecticide resistance limiting the effectiveness of insecticide-based vector control interventions,...<strong>Background: </strong><span><span><span><span>With the rapid expansion of insecticide resistance limiting the effectiveness of insecticide-based vector control interventions, integrated control strategies associating larviciding could be appropriate to improve current control efforts. The present experimental study assesses laboratory and field efficacy of the larvicide </span></span></span></span><span><span><span><span>VectoMax</span></span></span></span><span><span><span><span style="color:#111111;font-family:Roboto, sans-serif;font-size:16px;white-space:normal;background-color:#FFFFFF;"><sup>®</sup></span></span></span></span><span><span><span><span>G</span></span></span></span><span><span><span><span> on <i>Anopheline</i> and <i>Culicine</i> larval stages in Yaoundé. <strong>Methods:</strong> The effect of the larvicide </span></span></span></span><span><span><span><span>VectoMax</span></span></span></span><span><span><span><span style="color:#111111;font-family:Roboto, sans-serif;font-size:16px;white-space:normal;background-color:#FFFFFF;"><sup>®</sup></span></span></span></span><span><span><span><span>G,</span></span></span></span><span><span><span><span> a combination of <i>Bacillus</i><span> <i>thuringiensis</i> var. <i>israelensis</i> </span>(<i>Bti</i>) </span></span></span></span><span><span><span><span>and <i>Bacillus</i> <i>sphaericus</i> (<i>Bs</i>),</span></span></span></span><span><span><span><span> on larval development was assessed during both laboratory and open field trial experiments. Laboratory experiments permitted the evaluation of five different concentrations with four replicates/experiments. Laboratory experiments were conducted with <i>Anopheles</i> <i>coluzzii</i> “Ngousso” and <i>Culex</i> <i>quinquefasciatus</i> laboratory strains. Open field trials were conducted using </span></span></span></span><span><span><span><span>sixteen plastic containers with a diameter of 0.31 m buried in an array of four rows with 4 containers each. Distance between rows and between containers in a row was 1 meter. This experiment permitted to </span></span></span></span><span><span><span><span>test the effect of the microbial larvicide </span></span></span></span><span><span><span><span>VectoMax</span></span></span></span><span><span><span><span style="color:#111111;font-family:Roboto, sans-serif;font-size:16px;white-space:normal;background-color:#FFFFFF;"><sup>®</sup></span></span></span></span><span><span><span><span>G</span></span></span></span><span><span><span><span> under operational application conditions on field mosquito populations. <strong>Results:</strong> <span>The time to induce 100% mortality after exposure to serial concentrations of the larvicide varied according to the dose from 4 - 12 hours for <i>An.</i> <i>coluzzii</i> and 6 - 9 hours for <i>Cx.</i> <i>quinquefasciatus</i> in laboratory experiments. Measurements of the</span> residual activity indicated that all </span></span></span></span><span><span><span><span>VectoMax</span></span></span></span><span><span><span><span style="color:#111111;font-family:Roboto, sans-serif;font-size:16px;white-space:normal;background-color:#FFFFFF;"><sup>®</sup></span></span></span></span><span><span><span><span>G</span></span></span></span><span><span><span><span> concentrations were still active after 35 days and killed 86</span></span></span></span><span><span><span><span>% </span></span></span></span><span><span><span><span>-</span></span></span></span><span><span><span><span> </span></span></span></span><span><span><span><span>100% of larvae. Lethal dose of </span></span></span></span><span><span><span><span>VectoMax</span></span></span></span><span><span><span><span style="color:#111111;font-family:Roboto, sans-serif;font-size:16px;white-space:normal;background-color:#FFFFFF;"><sup>®</sup></span></span></span></span><span><span><span><span>G</span></span></span></span><span><span><span><span> killing 50% of larvae was estimated at 5.24 × 10<sup>-8</sup> mg/m<sup>2</sup> for <i>An.</i> <i>coluzzii</i> and 1.25 × 10<sup>-8</sup> mg/m<sup>2</sup> for <i>Cx.</i> <i>quinquefasciatus</i>. The lethal concentration inducing 95% mortality was estimated at 3.13 × 10<sup>-7</sup> mg/m<sup>2</sup> for <i>An.</i> <i>coluzzii</i> and 2.5 × 10<sup>-8</sup> <span>mg/m<sup>2</sup> for <i>Cx.</i> <i>quinquefasciatus</i>. Open field trials tests indicated that </span>sub-lethal concentrations of </span></span></span></span><span><span><span><span>VectoMax</span></span></span></span><span><span><span><span style="color:#111111;font-family:Roboto, sans-serif;font-size:16px;white-space:normal;background-color:#FFFFFF;"><sup>®</sup></span></span></span></span><span><span><span><span>G</span></span></span></span><span><span><span><span> successfully killed 100% <i>An.</i> <i>gambiae</i> s.l. larvae within 24 hours, while with <i>Culex</i> spp. larvae, 100% mortality was recorded after 48 hours post-treatment. Natural recolonization of water containers by larvae was recorded between 3 and 6 days respectively after the treatment with sublethal doses. Late instar larvae were recorded 5 and 6 days after treatment. When the jars were treated with reference dosage or supra doses of </span></span></span></span><span><span><span><span>VectoMax</span></span></span></span><span><span><span><span style="color:#111111;font-family:Roboto, sans-serif;font-size:16px;white-space:normal;background-color:#FFFFFF;"><sup>®</sup></span></span></span></span><span><span><span><span>G,</span></span></span></span><span><span><span><span> recolonization of water containers was observed six days after treatments. No pupae of both species were found 6 and 7 days post-treatment. <strong>Conclusions:</strong> The study indicated high efficacy of the microbial larvicide </span></span></span></span><span><span><span><span>VectoMax</span></span></span></span><span><span><span><span style="color:#111111;font-family:Roboto, sans-serif;font-size:16px;white-space:normal;background-color:#FFFFFF;"><sup>®</sup></span></span></span></span><span><span><span><span>G</span></span></span></span><span><span><span><span> against <i>Anopheline</i> and <i>Culex</i> larvae. Microbial larvicides such as </span></span></span></span><span><span><span><span>VectoMax</span></span></span></span><span><span><span><span style="color:#111111;font-family:Roboto, sans-serif;font-size:16px;white-space:normal;background-color:#FFFFFF;"><sup>®</sup></span></span></span></span><span><span><span><span>G</span></span></span></span><span><span><span><span> could be appropriate for controlling mosquito population particularly in areas experiencing high insecticide resistance or outdoor biting mosquitoes.</span></span></span></span>展开更多
Olfaction plays a major role in host-seeking behaviour of mosquitoes. An informat- ics-based genome-wide analysis of odorant-binding protein (OBP) homologues is under- taken, and 32 putative OBP genes in total in the ...Olfaction plays a major role in host-seeking behaviour of mosquitoes. An informat- ics-based genome-wide analysis of odorant-binding protein (OBP) homologues is under- taken, and 32 putative OBP genes in total in the whole genome sequences of Anopheles gam- biae are identified. Tissue-specific expression patterns of all A. gambiae OBP candidates are determined by semi-quantitative Reverse Transcription (RT)-PCR using mosquito actin gene a internal expression control standard. The results showed that 20 OBP candidates had strong expression in mosquito olfactory tissues (female antennae), which indicate that OBPs may play an important role in regulating mosquito olfactory behaviours. Species-specific expression pat- terns of all putative anopheline OBPs are also studied in two of the most important malaria vec- tors in A. gambiae complex, i.e. A. gambiae and A. arabiensis, which found 12 of the putative OBP genes examined displayed species-differential expression patterns. The cumulative relative expression intensity of the OBPs in A. arabiensis antennae was higher than that in A. gambiae (the ratio is 1441.45:1314.12), which might be due to their different host preference behaviour. While A. gambiae is a highly anthropophilic mosquito, A. arabiensis is more opportunistic (Vary- ing from anthropophilic to zoophilic). So the latter should need more OBPs to support its host selection preference. Identification of mosquito OBPs and verification of their tissue- and spe- cies-specific expression patterns represent the first step towards further molecular analysis of mosquito olfactory mechanism, such as recombinant expression and ligand identification.展开更多
Chemosensory proteins (CSPs) are identifiable by four spatially conserved Cys-teine residues in their primary structure or by two disulfide bridges in their tertiary structure according to the previously identified ol...Chemosensory proteins (CSPs) are identifiable by four spatially conserved Cys-teine residues in their primary structure or by two disulfide bridges in their tertiary structure according to the previously identified olfactory specific-D related proteins. A genomics- and bioinformatics-based approach is taken in the present study to identify the putative CSPs in the malaria-carrying mosquito, Anopheles gambiae. The results show that five out of the nine annotated candidates are the most possible Anopheles CSPs of A. gambiae. This study lays the foundation for further functional identification of Anopheles CSPs, though all of these candidates need additional experimental verification.展开更多
Chitin synthase （CHS） is an important enzyme catalyzing the formation of chitin polymers in all chitin containing organisms and a potential target site for insect pest control. However, our understanding of biochemi...Chitin synthase （CHS） is an important enzyme catalyzing the formation of chitin polymers in all chitin containing organisms and a potential target site for insect pest control. However, our understanding of biochemical properties of insect CHSs has been very limited. We here report enzymatic and inhibitory properties of CHS prepared from the African malaria mosquito, Anopheles gambiae. Our study, which represents the first time to use a nonradioactive method to assay CHS activity in an insect species, determined the optimal conditions for measuring the enzyme activity, including pH, temperature, and concentrations of the substrate uridine diphosphate N-acetyl-D-glucosamine （UDP- GlcNAc） and Mg＋＋. The optimal pH was about 6.5-7.0, and the highest activity was detected at temperatures between 37℃ and 44℃. Dithithreitol is required to prevent melanization of the enzyme extract. CHS activity was enhanced at low concentration of GIcNAc, but inhibited at high concentrations. Proteolytic activation of the activity is significant both in the 500×g supernatant and the 40 000×g pellet. Our study revealed only slight in vitro inhibition ofA. gambiae CHS activity by diflubenzuron and nikkomycin Z at the highest concentration （2.5μmol/L） examined. There was no in vitro inhibition by polyoxin D at any concentration examined. Furthermore, we did not observe any in vivo inhibition of CHS activity by any of these chemicals at any concentration examined. Our results suggest that the inhibition of chitin synthesis by these chemicals is not due to direct inhibition of CHS in A. gambiae.展开更多
Selenoprotein is biosynthesized by the incorporation of selenocysteine into proteins,where the TGA codon in the open reading frame does not act as a stop signal but is translated into selenocysteine.The dual functions...Selenoprotein is biosynthesized by the incorporation of selenocysteine into proteins,where the TGA codon in the open reading frame does not act as a stop signal but is translated into selenocysteine.The dual functions of TGA result in mis-annotation or lack of selenoproteins in the sequenced genomes of many species.Available computational tools fail to correctly predict selenoproteins.Thus,we devel-oped a new method to identify selenoproteins from the genome of Anopheles gambiae computationally.Based on released genomic information,several programs were edited with PERL language to identify selenocysteine insertion sequence(SECIS)element,the coding potential of TGA codons,and cys-teine-containing homologs of selenoprotein genes.Our results showed that 11365 genes were termi-nated with TGA codons,918 of which contained SECIS elements.Similarity search revealed that 58 genes contained Sec/Cys pairs and similar flanking regions around in-frame TGA codons.Finally,7 genes were found to fully meet requirements for selenoproteins,although they have not been anno-tated as selenoproteins in NCBI databases.Deduced from their basic properties,the newly found se-lenoproteins in the genome of Anopheles gambiae are possibly related to in vivo oxidation tolerance and protein regulation in order to interfere with anopheles' vectorial capacity of Plasmodium.This study may also provide theoretical bases for the prevention of malaria from anopheles transmission.展开更多
Anopheles gambiae and Anopheles coluzzii are closely related species that are predominant vectors of malaria in Africa.Recently,A.gambiae form M was renamed A.coluzzii and we now conclude on the basis of a diagnostic ...Anopheles gambiae and Anopheles coluzzii are closely related species that are predominant vectors of malaria in Africa.Recently,A.gambiae form M was renamed A.coluzzii and we now conclude on the basis of a diagnostic PCR-restriction fragment length polymorphism assay that Ag55 cells were derived from A.coluzzii.We established an Ag55 cell transcriptome,and KEGG pathway analysis showed that Ag55 cells are enriched in phagosome pathway transcripts.The Ag55 transcriptome has an abundance of specific transcripts characteristic of mosquito hemocytes.Functional E.coli bioparticle uptake experiments visualized by fluorescence microscopy and confocal microscopy and quantified by flow cytometry establish the phagocytic competence of Ag55 cells.Results from this investigation of Ag55 cell properties will guide researchers in the use and engineering of the Ag55 cell line to better enable investigations of Plasmodium,other microbes,and insecticidal toxins.展开更多
Infections by mosquito-borne diseases represent one of the leading causes of death in third world countries.The rapid progression of resistance to conventional insecticide causes a significant threat to the highly eff...Infections by mosquito-borne diseases represent one of the leading causes of death in third world countries.The rapid progression of resistance to conventional insecticide causes a significant threat to the highly efficient preventive methods currently in place.Insect neuropeptidergic system offers potential targets to control the insect vectors.The essential roles of the neuropeptide ecdysis triggering hormone(ETH)in insect development and reproduction led us to attempt understanding of the fundamentals of the biochemical interaction between ETH and its receptor in the African malaria mosquito Anopheles gambiae.One of two ETH peptides of the African malaria mosquito(AgETH1),a small peptide hormone with 17 amino acid residues(SESPGFFIKLSKSVPRI-NH2),was studied to elucidate its molecular structure.N-termini deletions and mutations of conserved amino acids in the ligand revealed the critical residues for the receptor activation.The solution structure of AgETH1 using 2D 1H-1H nuclear magnetic resonance(NMR)spectroscopy and nuclear overhauser effect(NOE)derived constraints revealed a short alpha helix between residues 3S and 11S.The NMR solution structure of AgETH1 will be of significant assistance for designing a new class of insecticidal compounds that acts on the AgETH receptor aiming for in silico docking studies.展开更多
Background:Mosquitoes have developed resistance against pyrethroids,the only class of insecticides approved for use on long-lasting insecticidal nets(LLINs).The present study sought to evaluate the efficacy of the pyr...Background:Mosquitoes have developed resistance against pyrethroids,the only class of insecticides approved for use on long-lasting insecticidal nets(LLINs).The present study sought to evaluate the efficacy of the pyrethroid synergist PermaNet^(■)3.0 LLIN versus the pyrethroid-only PermaNet^(■)2.0 LLIN,in an East African hut design in Lower Moshi,northern Tanzania.In this setting,resistance to pyrethroid insecticides has been identified in Anopheles gambiae mosquitoes.Methods:Standard World Health Organization bioefficacy evaluations were conducted in both laboratory and experimental huts.Experimental hut evaluations were conducted in an area where there was presence of a population of highly pyrethroid-resistant An.arabiensis mosquitoes.All nets used were subjected to cone bioassays and then to experimental hut trials.Mosquito mortality,blood-feeding inhibition and personal protection rate were compared between untreated nets,unwashed LLINs and LLINs that were washed 20 times.Results:Both washed and unwashed PermaNet^(■)2.0 and PermaNet^(■)3.0 LLINs had knockdown and mortality rates of 100%against a susceptible strain of An.gambiae sensu stricto.The adjusted mortality rate of the wild mosquito population after use of the unwashed PermaNet^(■)3.0 and PermaNet^(■)2.0 nets was found to be higher than after use of the washed PermaNet^(■)2.0 and PermaNet^(■)3.0 nets.Conclusions:Given the increasing incidence of pyrethroid resistance in An.gambiae mosquitoes in Tanzania,we recommend that consideration is given to its distribution in areas with pyrethroid-resistant malaria vectors within the framework of a national insecticide-resistance management plan.展开更多
Objective:To evaluate the insecticidal potential of Alstonia boonei(A.boonei)oils and derivatives against different life stages of a malaria vector,Anopheles gambiae.Methods:The leaf,stem bark and root bark of A.boone...Objective:To evaluate the insecticidal potential of Alstonia boonei(A.boonei)oils and derivatives against different life stages of a malaria vector,Anopheles gambiae.Methods:The leaf,stem bark and root bark of A.boonei were collected from an open field and air dried before being blended to fine powder.Oils from this plant were extracted by cold extraction and were prepared at different concentrations.Contact toxicity of A.boonei was tested against the larvae and pupae of the insect while smoke toxicity of the plant materials in form of mosquito coil was tested against the adult insect.Results:Alstodine recorded the highest insect mortality rate and the order of susceptibility of the life stages of the insect to the plant was pupae<adult<larvae.Alstodine recorded the highest repellant activity(100%)after 4-5 h of application.However,all the treatments achieved high repellency(above 70%)after 6-7 h of application compared with the control.The formulated mosquito coil(smoke)of A.boonei oil extracts and derivatives showed high rate of protectability as they achieved above 55%protection.Moreover,alstodine(83.22%)showed the greatest smoke toxicity effect on the insect as it recorded almost the same percentage protection as the positive control(Raid synthetic insecticide)which recorded 83.56%protection.Conclusions:This present study has proven A.boonei oil extracts and derivatives as a potential botanical insecticide which could serve as a new thoroughfare of mosquito control.Moreover,the order of effectiveness of the plant can be arranged thus:alstodine>alstonine>stem bark extract>leaf extract>root bark extract.展开更多
Objective:To explore ovariole basal body granulations and follicular dilatations for determining physiological age inAnopheles gambiaes.s.(An.gambiaes.s.).Methods:Mosquitoes were collected by using window trap catch a...Objective:To explore ovariole basal body granulations and follicular dilatations for determining physiological age inAnopheles gambiaes.s.(An.gambiaes.s.).Methods:Mosquitoes were collected by using window trap catch and identified morphologically.For the first lot ofmosquitoes,they were dissected,and ovary was left in distilled water for reading ovarian tracheoles and the second was cut and transferred to another blade in a physiological liquid for verification of ovariole basal body granulations.The same approach was followed with the second lot of mosquitoes where follicular dilatations were found after classic dilaceration of ovaries were transferred into physiological liquid.The other body parts of mosquitoes were used to identify the species of theAn.gambiaes.s.complex by PCR.Results:Among the 123An.gambiae s.s.of the first lot,the method of Detinova determined the age of 89 mosquitoes versus 114 for the observation of granulations(P>0.05).Among the 112An.gambiae s.s.of the second lot,the method of Detinova determined the age of 84 mosquitoes versus 93 for the observation of follicular dilatations(P>0.05).Unlike the method of Detinova,observation of follicular dilatations and basal body granulations of ovarioles were possible beyond the stage II Christophers.Conclusions:Overall,the observation of follicular dilatations and ovariole basal body granulations are reliable for the determination of the physiological age inAn.gambiaes.s.Furthermore,these two methods can be used beyond the stage II.展开更多
Background:Anopheles gambiae(An.gambiae)is considered the most effective malaria vector worldwide and is widely distributed in Africa.The purpose of this study is to determine the potential impact of climate change on...Background:Anopheles gambiae(An.gambiae)is considered the most effective malaria vector worldwide and is widely distributed in Africa.The purpose of this study is to determine the potential impact of climate change on An.gambiae and predict the present and future potential suitable habitat globally.Methods:In this study,environmental variables,global occurrence data of An.gambiae,and the maximum entropy model(MaxEnt)were used to evaluate the contribution of environmental factors and predict the habitat suitability of An.gambiae under the current and future scenarios.Results:Among all environmental variables,isothermality(Bio3,34.5%)contributed the most to An.gambiae distribution.Under current climate conditions,the potential suitable areas for An.gambiae are mainly located near the equator(approximately 30°N-30°S),with a total area of 16.58 million km2,including central and northern South America,a fraction of areas near the equator of North America,central and southern Africa,some tropical regions of southern Asia,and small areas of Oceania.The areas of potential suitable habitats would be reduced to varying degrees in future climate scenarios.Conclusions:Potential suitable habitats for An.gambiae may not be limited to Africa.Necessary surveillance and preventive measures should be undertaken in high-risk regions,including those outside Africa,to monitor and control the spread of An.gambiae.展开更多
Anopheles funestus and Anopheles gambiae are malaria vector mosquitoes. Knowing their resting behavior is important for implementing control methods. The aim of this study was to investigate the resting behaviour of t...Anopheles funestus and Anopheles gambiae are malaria vector mosquitoes. Knowing their resting behavior is important for implementing control methods. The aim of this study was to investigate the resting behaviour of the two malaria mosquitoes. The study was conducted in Kilombero River Valley and mosquitoes were collected using indoor and outdoor traps from 2012-2015. Poisson mixed models were used to quantify the impact of environment variables on resting behaviour. A log ratio rate between the type of trap and its interaction with environmental variables was used to determine if there was a change over time in the resting behaviour. A total of 4696 mosquitoes were resting indoors of which 57% were A. funestus and 43% were A. gambiae. Similarly, a total of 12,028 mosquitoes were resting outdoor of which 13% were A. funestus and 87% were A. gambiae. Temperature was significant and affected the resting behaviour of A. funestus. Humidity, saturation deficit and temperature were significant variables influencing the resting behaviour of A. gambiae. A. funestus was resting indoor while A. gambiae was resting outdoor over time generally. The findings of this study on the effects of environmental variables and the variations in the resting behaviour of A. gambiae and A. funestus could be used as a guide to implementing appropriate intervention measures such as indoor residential spraying (IRS), insecticide treated nets (ITNs) and mosquito repellents.展开更多
文摘Malaria incidence in urban areas has generally been low compared to rural areas but recent data indicate that urban malaria remains a public health problem. It is therefore important to understand the factors that promote urban malaria to help formulate future vector control strategies. This study compared Anopheles gambiae s.l. (A. gambiae s.l.) species composition, distribution and insecticide resistance mechanisms between vegetable and non-vegetable growing areas in Accra Metropolis. Four sites were selected within the city of Accra which comprised of two vegetable-growing and two non-vegetable growing areas. WHO susceptibility tests were carried out on adults A. gambiae s.l. reared from larvae collected from the sites. Five insecticides were tested and the A. gambiae complex, resistance genotypes and enzyme activities of each population were characterized. All A. gambiae s.l. populations tested were resistant to all the insecticides, but relatively lower mortalities were observed in the vegetable growing areas. The mortality against 0.05% deltamethrin was 2.6% (Opeibea) and 12.5% (Korle-Bu) for the vegetable growing areas and 36.2% (Achimota) and 38.9% (Mataheko) in the non-vegetable growing areas. Anopheles gambiae s.s. (95% of Opeibea population) and Anopheles coluzzii, (98% of Korle-Bu population) were the dominant species in the vegetable growing areas. The voltage-gated sodium channel (Vgsc-1014F) frequencies of all the populations were similar but the acetylcholinesterase (ace-1) frequencies were significantly lower (p A. gambiae s.l. from Opeibea than from the other areas. The contribution of urban agriculture in the development of insecticide resistance needs to be considered in the formulation of future vector control strategies alongside other domestic usages.
基金Supported by Conselho Nacional de Desenvolvimento Cientifico e Tecnologico,Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior,and Fundacao de Apoio a Pesquisa e Inovacao Tecnol'ogica do Estado de Sergipe(Grant#475520/2012-2)
文摘Objective:To evaluate the larvicidal efficacy of eight volatile components of essential oils against 3rd instar larvae of Anopheles gambiae s.s.Methods:Larvicidal effects of each compound were evaluated in both laboratory and semi-field trials.Stock solution was prepared and serial dilutions were made in six concentrations for each compound.A total of 20 larvae were exposed to larvicides for each replicate and monitored at intervals of 12,24,48 and 72 h.Larvae monitoring was done on basis of dead and live larvae in all intervals.Results:All assayed compounds were larvicides and presented varying degrees of larval toxicity,with LC_(50)values ranging from 1.28 to 1938.92 mg/L depending on the treatment time(12,24,48 or 72 h).(-)-Perillyl alcohol presented the strongest larvicidal activity towards Anopheles gambiae larvae,with LC_(50)values of 73.60,18.36,1.72 and1.28 mg/L after 12,24,48 and 72 h of exposure,respectively.The next strongest were(-)-isopulegol(LC_(50)=135.10,49.39,34.39 and 20.22 mg/L)and(-)-carvone epoxide(LC_(50)=168.86,124.74,80.84 and 23.46 mg/L).After 12,24 and 48 h of treatment,hydroxydihydrocarvone was the least toxic compound,with LC_(50)values of 1938.92,1172.18 and 401.03 mg/L,respectively.Conclusions:The data obtained in this study suggest that all evaluated monoterpenes,especially(-)-perillyl alcohol,have remarkable larvicidal effects and may be considered as potential sources for the development of suitable natural larvicides for mosquito management programs.Further small-scale field trials should be conducted.
文摘Objective:To screen phytochemicals in ethanolic leaf extracts of Phyllanthus amarus collected from three different geographical zones in Nigeria and evaluate their effects on larva and adult of Anopheles gambiae.Methods:The sample extracts of Phyllanthus amarus prepared with ethanol solvent were tested against Anopheles gambiae at two important developmental stages of its life cycle using slightly modified WHO protocols.Results:Alkaloids,saponins,tannins,flavonoids,glycosides,phenols,and terpenes were detected in each extract.Among these samples,the extract from northwest exhibited the highest larvicidal activity(LC50=263.02 ppm),followed by southeast and southwest extracts(LC50=288.40 and 295.12 ppm,respectively after 48 h),while the extract from southwest exhibited the highest adulticidal activity(LC50=275.42 ppm),followed by northwest and southeast extract(LC50=301.99 and 316.22 ppm,respectively after 24 h).A 50%larva mortality was almost attained at 600 ppm after 48 h duration of exposure to the northwest extract.Conclusions:The tested samples possess strong larvicidal and adulticidal property against Anopheles gambiae which depends on their chemical composition and localities of collection.Further studies are needed to explore the insecticidal activity against a wider range of mosquito species,and to identify active ingredient(s)of the extract responsible for such activity.
文摘Understanding the genetic architecture of indi-vidual taxa of medical importance is the first step for designing disease preventive strategies. To understand the genetic details and evolu-tionary perspective of the model malaria vector, Anopheles gambiae and to use the information in other species of local importance, we scanned the published X-chromosome se-quence for detail characterization and obtain evolutionary status of different genes. The te-locentric X-chromosome contains 106 genes of known functions and 982 novel genes. Majori-ties of both the known and novel genes are with introns. The known genes are strictly biased towards less number of introns;about half of the total known genes have only one or two in-trons. The extreme sized (either long or short) genes were found to be most prevalent (58% short and 23% large). Statistically significant positive correlations between gene length and intron length as well as with intron number and intron length were obtained signifying the role of introns in contributing to the overall size of the known genes of X-chromosome in An. gam-biae. We compared each individual gene of An. gambiae with 33 other taxa having whole ge-nome sequence information. In general, the mosquito Aedes aegypti was found to be ge-netically closest and the yeast Saccharomyces cerevisiae as most distant taxa to An. gambiae. Further, only about a quarter of the known genes of X-chromosome were unique to An. gambiae and majorities have orthologs in dif-ferent taxa. A phylogenetic tree was constructed based on a single gene found to be highly orthologous across all the 34 taxa. Evolutionary relationships among 13 different taxa were in-ferred which corroborate the previous and pre-sent findings on genetic relationships across various taxa.
文摘The progress in the field of nanotechnology has contributed to the development of tools for combating the most critical problems in developing countries. The requirements that such tools should meet are low-cost and resource settings, environmental protection, ease of use, and availability. The use of plant properties for the generation of nanoparticles (NPs), which serve as bioinsecticides to combat the plasticity and resistance of mosquitoes and parasites, is considered possible. Here, we report for the first time the larvicidal activity of silver (Ag) NPs (AgNPs) synthesized from Psidium guajava (P. guajava) extract, which targets the 4th instar larvae of Anopheles gambiae. Concentrations of AgNPs between 0 and 200 ppm were used and their LC50 at 24 h and 48 h were determined as 19.55 ppm and 8.737 ppm, respectively. The AgNPs were stable and highly effective against the larvae of A. gambiae and thereby we anticipate that they can be used to combat vector-borne diseases in developing countries.
文摘The epsilon class glutathione-S-transferase of Anopheles gambiae, agGSTe2, is capable of metabolizing DDT. A molecular docking analysis of DDT with agGSTe2 support an E2 elimination mechanism wherein the glutathione sulfur serves as the base to convert DDT to DDE.
文摘Background: Mosquitoes are responsible of numerous vector-borne diseases and among these diseases is malaria which takes away lives of thousands of people, especially children of under five, particularly in Africa. To reduce the mortality and economic burdens of this deadly disease, synthetic insecticide has been of use to control its main vector, Anopheles gambiae. Due to adverse effects caused by these conventional products on non-target organisms and the environment, plants have been of first choice as they proved their effectiveness against mosquitoes and are said to be eco-friendly and relatively safer. Therefore, the aim of this study was to screen the phytochemicals and determine the larvicidal and adult emergence exhibitory activities of Momordica charantia and Hyptis spicigera leaves extracts against Anopheles gambiae larvae. Methods: The WHO standard protocol for larvicidal activity and IGRs was followed up and concentrations from 500 - 2000 ppm for larvicidal and 500 - 1500 ppm for IGRs were set up. Results: There was the presence of alkaloids, flavonoids, tannins, phenols, steroids, terpenoids and oils in Momordica charantia against alkaloids, taponins, tannins, phenols, steroids, terpenoids and oils in Hyptis spicigera. Methanol crude extract registered the lowest LC<sub>50</sub> value of 270.6 ppm followed by ethyl acetate and hexane fractions recorded the LC<sub>50</sub> of 742.1 and 756 ppm, respectively for larvicidal activity of Momordica charantia against LC<sub>50</sub> of 760 and 867.5 ppm for hexane fraction and methanol crude extract, respectively for Hyptis spicigera. Methanol crude extract and hexane fraction of both plants as well as the ethyl acetate fraction of M. charantia registered greater emergence inhibition with IE<sub>50</sub> values of 590.2, 842.3 and 982 ppm for methanol crude extract, hexane and ethyl acetate fractions of M. charantia, respectively against 901.7 and 873.2 for methanol crude extract and hexane fraction of H. spicigera, respectively. Conclusion: The toxicity and adult emergence inhibition may be associated with constituents in both plants that interfere with the normal neuronal, respiratory and endocrine systems functions.
文摘Background: Anopheles gambiae is enemy number one of mankind in Africa and particularly in Cameroon due to its ability of transmitting malaria which is the deadliest disease in this part of the world. Synthetic insecticides have been used to control malaria vectors but they have negative effects on non-target organisms and are environmentally unfriendly. Control of mosquitoes at larval stages using phytochemicals is currently the leading tool to reduce the mosquito population and so the reduction of malaria transmission rates. Therefore, the present study was to evaluate the phytochemical contents, larvicidal and adult emergence inhibition activities of Balanites aegyptiaca seed and Aristolochia albida root solvents extracts against Anopheles gambiae larvae. Methods: The World Health Organization standard protocols were followed for the different bioassays. Concentrations ranging from 500 - 2000 ppm for larvicidal and 500 - 1500 ppm for IGRs were used. Results: Both plants showed the presence of alkaloids, flavonoids, saponins, tannins, phenols, terpenoids and oils except the absence of phenols in Aristolochia albida. The larvicidal activity of Aristolochia albida extracts showed that hexane and methanol fractions were the most active killing relatively all exposed larvae with the LC<sub>50</sub> values of 420.1 and 453 ppm, respectively. The same observation was made in hexane fraction from Balanites aegyptiaca (LC<sub>50</sub> = 588 ppm). The insect growth inhibitory activity of Aristolochia albida extracts proved that hexane and methanol fractions relatively caused a 100% inhibition in the mosquito development, recording the EI<sub>50</sub> values of 482.4 and 555.6 ppm, respectively. The same trend was observed with Balanites aegyptiaca hexane fraction registering better EI<sub>50</sub> of 623.9 ppm. Conclusions: Our findings demonstrate that Balanites aegyptiaca seed and Aristolochia albida seed extracts are rich in phytochemicals capable of killing mosquito larvae and disrupting mosquito larval development. This could contribute to the control of mosquito populations and improved management of malaria.
文摘<strong>Background: </strong><span><span><span><span>With the rapid expansion of insecticide resistance limiting the effectiveness of insecticide-based vector control interventions, integrated control strategies associating larviciding could be appropriate to improve current control efforts. The present experimental study assesses laboratory and field efficacy of the larvicide </span></span></span></span><span><span><span><span>VectoMax</span></span></span></span><span><span><span><span style="color:#111111;font-family:Roboto, sans-serif;font-size:16px;white-space:normal;background-color:#FFFFFF;"><sup>®</sup></span></span></span></span><span><span><span><span>G</span></span></span></span><span><span><span><span> on <i>Anopheline</i> and <i>Culicine</i> larval stages in Yaoundé. <strong>Methods:</strong> The effect of the larvicide </span></span></span></span><span><span><span><span>VectoMax</span></span></span></span><span><span><span><span style="color:#111111;font-family:Roboto, sans-serif;font-size:16px;white-space:normal;background-color:#FFFFFF;"><sup>®</sup></span></span></span></span><span><span><span><span>G,</span></span></span></span><span><span><span><span> a combination of <i>Bacillus</i><span> <i>thuringiensis</i> var. <i>israelensis</i> </span>(<i>Bti</i>) </span></span></span></span><span><span><span><span>and <i>Bacillus</i> <i>sphaericus</i> (<i>Bs</i>),</span></span></span></span><span><span><span><span> on larval development was assessed during both laboratory and open field trial experiments. Laboratory experiments permitted the evaluation of five different concentrations with four replicates/experiments. Laboratory experiments were conducted with <i>Anopheles</i> <i>coluzzii</i> “Ngousso” and <i>Culex</i> <i>quinquefasciatus</i> laboratory strains. Open field trials were conducted using </span></span></span></span><span><span><span><span>sixteen plastic containers with a diameter of 0.31 m buried in an array of four rows with 4 containers each. Distance between rows and between containers in a row was 1 meter. This experiment permitted to </span></span></span></span><span><span><span><span>test the effect of the microbial larvicide </span></span></span></span><span><span><span><span>VectoMax</span></span></span></span><span><span><span><span style="color:#111111;font-family:Roboto, sans-serif;font-size:16px;white-space:normal;background-color:#FFFFFF;"><sup>®</sup></span></span></span></span><span><span><span><span>G</span></span></span></span><span><span><span><span> under operational application conditions on field mosquito populations. <strong>Results:</strong> <span>The time to induce 100% mortality after exposure to serial concentrations of the larvicide varied according to the dose from 4 - 12 hours for <i>An.</i> <i>coluzzii</i> and 6 - 9 hours for <i>Cx.</i> <i>quinquefasciatus</i> in laboratory experiments. Measurements of the</span> residual activity indicated that all </span></span></span></span><span><span><span><span>VectoMax</span></span></span></span><span><span><span><span style="color:#111111;font-family:Roboto, sans-serif;font-size:16px;white-space:normal;background-color:#FFFFFF;"><sup>®</sup></span></span></span></span><span><span><span><span>G</span></span></span></span><span><span><span><span> concentrations were still active after 35 days and killed 86</span></span></span></span><span><span><span><span>% </span></span></span></span><span><span><span><span>-</span></span></span></span><span><span><span><span> </span></span></span></span><span><span><span><span>100% of larvae. Lethal dose of </span></span></span></span><span><span><span><span>VectoMax</span></span></span></span><span><span><span><span style="color:#111111;font-family:Roboto, sans-serif;font-size:16px;white-space:normal;background-color:#FFFFFF;"><sup>®</sup></span></span></span></span><span><span><span><span>G</span></span></span></span><span><span><span><span> killing 50% of larvae was estimated at 5.24 × 10<sup>-8</sup> mg/m<sup>2</sup> for <i>An.</i> <i>coluzzii</i> and 1.25 × 10<sup>-8</sup> mg/m<sup>2</sup> for <i>Cx.</i> <i>quinquefasciatus</i>. The lethal concentration inducing 95% mortality was estimated at 3.13 × 10<sup>-7</sup> mg/m<sup>2</sup> for <i>An.</i> <i>coluzzii</i> and 2.5 × 10<sup>-8</sup> <span>mg/m<sup>2</sup> for <i>Cx.</i> <i>quinquefasciatus</i>. Open field trials tests indicated that </span>sub-lethal concentrations of </span></span></span></span><span><span><span><span>VectoMax</span></span></span></span><span><span><span><span style="color:#111111;font-family:Roboto, sans-serif;font-size:16px;white-space:normal;background-color:#FFFFFF;"><sup>®</sup></span></span></span></span><span><span><span><span>G</span></span></span></span><span><span><span><span> successfully killed 100% <i>An.</i> <i>gambiae</i> s.l. larvae within 24 hours, while with <i>Culex</i> spp. larvae, 100% mortality was recorded after 48 hours post-treatment. Natural recolonization of water containers by larvae was recorded between 3 and 6 days respectively after the treatment with sublethal doses. Late instar larvae were recorded 5 and 6 days after treatment. When the jars were treated with reference dosage or supra doses of </span></span></span></span><span><span><span><span>VectoMax</span></span></span></span><span><span><span><span style="color:#111111;font-family:Roboto, sans-serif;font-size:16px;white-space:normal;background-color:#FFFFFF;"><sup>®</sup></span></span></span></span><span><span><span><span>G,</span></span></span></span><span><span><span><span> recolonization of water containers was observed six days after treatments. No pupae of both species were found 6 and 7 days post-treatment. <strong>Conclusions:</strong> The study indicated high efficacy of the microbial larvicide </span></span></span></span><span><span><span><span>VectoMax</span></span></span></span><span><span><span><span style="color:#111111;font-family:Roboto, sans-serif;font-size:16px;white-space:normal;background-color:#FFFFFF;"><sup>®</sup></span></span></span></span><span><span><span><span>G</span></span></span></span><span><span><span><span> against <i>Anopheline</i> and <i>Culex</i> larvae. Microbial larvicides such as </span></span></span></span><span><span><span><span>VectoMax</span></span></span></span><span><span><span><span style="color:#111111;font-family:Roboto, sans-serif;font-size:16px;white-space:normal;background-color:#FFFFFF;"><sup>®</sup></span></span></span></span><span><span><span><span>G</span></span></span></span><span><span><span><span> could be appropriate for controlling mosquito population particularly in areas experiencing high insecticide resistance or outdoor biting mosquitoes.</span></span></span></span>
文摘Olfaction plays a major role in host-seeking behaviour of mosquitoes. An informat- ics-based genome-wide analysis of odorant-binding protein (OBP) homologues is under- taken, and 32 putative OBP genes in total in the whole genome sequences of Anopheles gam- biae are identified. Tissue-specific expression patterns of all A. gambiae OBP candidates are determined by semi-quantitative Reverse Transcription (RT)-PCR using mosquito actin gene a internal expression control standard. The results showed that 20 OBP candidates had strong expression in mosquito olfactory tissues (female antennae), which indicate that OBPs may play an important role in regulating mosquito olfactory behaviours. Species-specific expression pat- terns of all putative anopheline OBPs are also studied in two of the most important malaria vec- tors in A. gambiae complex, i.e. A. gambiae and A. arabiensis, which found 12 of the putative OBP genes examined displayed species-differential expression patterns. The cumulative relative expression intensity of the OBPs in A. arabiensis antennae was higher than that in A. gambiae (the ratio is 1441.45:1314.12), which might be due to their different host preference behaviour. While A. gambiae is a highly anthropophilic mosquito, A. arabiensis is more opportunistic (Vary- ing from anthropophilic to zoophilic). So the latter should need more OBPs to support its host selection preference. Identification of mosquito OBPs and verification of their tissue- and spe- cies-specific expression patterns represent the first step towards further molecular analysis of mosquito olfactory mechanism, such as recombinant expression and ligand identification.
文摘Chemosensory proteins (CSPs) are identifiable by four spatially conserved Cys-teine residues in their primary structure or by two disulfide bridges in their tertiary structure according to the previously identified olfactory specific-D related proteins. A genomics- and bioinformatics-based approach is taken in the present study to identify the putative CSPs in the malaria-carrying mosquito, Anopheles gambiae. The results show that five out of the nine annotated candidates are the most possible Anopheles CSPs of A. gambiae. This study lays the foundation for further functional identification of Anopheles CSPs, though all of these candidates need additional experimental verification.
文摘Chitin synthase （CHS） is an important enzyme catalyzing the formation of chitin polymers in all chitin containing organisms and a potential target site for insect pest control. However, our understanding of biochemical properties of insect CHSs has been very limited. We here report enzymatic and inhibitory properties of CHS prepared from the African malaria mosquito, Anopheles gambiae. Our study, which represents the first time to use a nonradioactive method to assay CHS activity in an insect species, determined the optimal conditions for measuring the enzyme activity, including pH, temperature, and concentrations of the substrate uridine diphosphate N-acetyl-D-glucosamine （UDP- GlcNAc） and Mg＋＋. The optimal pH was about 6.5-7.0, and the highest activity was detected at temperatures between 37℃ and 44℃. Dithithreitol is required to prevent melanization of the enzyme extract. CHS activity was enhanced at low concentration of GIcNAc, but inhibited at high concentrations. Proteolytic activation of the activity is significant both in the 500×g supernatant and the 40 000×g pellet. Our study revealed only slight in vitro inhibition ofA. gambiae CHS activity by diflubenzuron and nikkomycin Z at the highest concentration （2.5μmol/L） examined. There was no in vitro inhibition by polyoxin D at any concentration examined. Furthermore, we did not observe any in vivo inhibition of CHS activity by any of these chemicals at any concentration examined. Our results suggest that the inhibition of chitin synthesis by these chemicals is not due to direct inhibition of CHS in A. gambiae.
基金the National Natural Science Foundation of China (Grant Nos. 30370352 and 30570420)
文摘Selenoprotein is biosynthesized by the incorporation of selenocysteine into proteins,where the TGA codon in the open reading frame does not act as a stop signal but is translated into selenocysteine.The dual functions of TGA result in mis-annotation or lack of selenoproteins in the sequenced genomes of many species.Available computational tools fail to correctly predict selenoproteins.Thus,we devel-oped a new method to identify selenoproteins from the genome of Anopheles gambiae computationally.Based on released genomic information,several programs were edited with PERL language to identify selenocysteine insertion sequence(SECIS)element,the coding potential of TGA codons,and cys-teine-containing homologs of selenoprotein genes.Our results showed that 11365 genes were termi-nated with TGA codons,918 of which contained SECIS elements.Similarity search revealed that 58 genes contained Sec/Cys pairs and similar flanking regions around in-frame TGA codons.Finally,7 genes were found to fully meet requirements for selenoproteins,although they have not been anno-tated as selenoproteins in NCBI databases.Deduced from their basic properties,the newly found se-lenoproteins in the genome of Anopheles gambiae are possibly related to in vivo oxidation tolerance and protein regulation in order to interfere with anopheles' vectorial capacity of Plasmodium.This study may also provide theoretical bases for the prevention of malaria from anopheles transmission.
基金The project was supported by the University of Georgia College of Agricultureand Environmental Sciences.
文摘Anopheles gambiae and Anopheles coluzzii are closely related species that are predominant vectors of malaria in Africa.Recently,A.gambiae form M was renamed A.coluzzii and we now conclude on the basis of a diagnostic PCR-restriction fragment length polymorphism assay that Ag55 cells were derived from A.coluzzii.We established an Ag55 cell transcriptome,and KEGG pathway analysis showed that Ag55 cells are enriched in phagosome pathway transcripts.The Ag55 transcriptome has an abundance of specific transcripts characteristic of mosquito hemocytes.Functional E.coli bioparticle uptake experiments visualized by fluorescence microscopy and confocal microscopy and quantified by flow cytometry establish the phagocytic competence of Ag55 cells.Results from this investigation of Ag55 cell properties will guide researchers in the use and engineering of the Ag55 cell line to better enable investigations of Plasmodium,other microbes,and insecticidal toxins.
基金supported by National Institutes of Health(NIH)grants NIH-NIAID R21 AI135457 and AI163423,1S10OD026726 and USDA-NIFA,GRANT13066347thank the Terry Johnson Cancer Research Center of Kansas State University and K-INBRE(NIH Grant P20GM103418)programs for supporting NMR studies.Contribution number 22-200-J from the Kansas Agricultural Experiment Station.
文摘Infections by mosquito-borne diseases represent one of the leading causes of death in third world countries.The rapid progression of resistance to conventional insecticide causes a significant threat to the highly efficient preventive methods currently in place.Insect neuropeptidergic system offers potential targets to control the insect vectors.The essential roles of the neuropeptide ecdysis triggering hormone(ETH)in insect development and reproduction led us to attempt understanding of the fundamentals of the biochemical interaction between ETH and its receptor in the African malaria mosquito Anopheles gambiae.One of two ETH peptides of the African malaria mosquito(AgETH1),a small peptide hormone with 17 amino acid residues(SESPGFFIKLSKSVPRI-NH2),was studied to elucidate its molecular structure.N-termini deletions and mutations of conserved amino acids in the ligand revealed the critical residues for the receptor activation.The solution structure of AgETH1 using 2D 1H-1H nuclear magnetic resonance(NMR)spectroscopy and nuclear overhauser effect(NOE)derived constraints revealed a short alpha helix between residues 3S and 11S.The NMR solution structure of AgETH1 will be of significant assistance for designing a new class of insecticidal compounds that acts on the AgETH receptor aiming for in silico docking studies.
基金The study was financially supported by Vestergaard Frandsen,Aarhus,Denmark.The funding body had no influence on this publication.
文摘Background:Mosquitoes have developed resistance against pyrethroids,the only class of insecticides approved for use on long-lasting insecticidal nets(LLINs).The present study sought to evaluate the efficacy of the pyrethroid synergist PermaNet^(■)3.0 LLIN versus the pyrethroid-only PermaNet^(■)2.0 LLIN,in an East African hut design in Lower Moshi,northern Tanzania.In this setting,resistance to pyrethroid insecticides has been identified in Anopheles gambiae mosquitoes.Methods:Standard World Health Organization bioefficacy evaluations were conducted in both laboratory and experimental huts.Experimental hut evaluations were conducted in an area where there was presence of a population of highly pyrethroid-resistant An.arabiensis mosquitoes.All nets used were subjected to cone bioassays and then to experimental hut trials.Mosquito mortality,blood-feeding inhibition and personal protection rate were compared between untreated nets,unwashed LLINs and LLINs that were washed 20 times.Results:Both washed and unwashed PermaNet^(■)2.0 and PermaNet^(■)3.0 LLINs had knockdown and mortality rates of 100%against a susceptible strain of An.gambiae sensu stricto.The adjusted mortality rate of the wild mosquito population after use of the unwashed PermaNet^(■)3.0 and PermaNet^(■)2.0 nets was found to be higher than after use of the washed PermaNet^(■)2.0 and PermaNet^(■)3.0 nets.Conclusions:Given the increasing incidence of pyrethroid resistance in An.gambiae mosquitoes in Tanzania,we recommend that consideration is given to its distribution in areas with pyrethroid-resistant malaria vectors within the framework of a national insecticide-resistance management plan.
文摘Objective:To evaluate the insecticidal potential of Alstonia boonei(A.boonei)oils and derivatives against different life stages of a malaria vector,Anopheles gambiae.Methods:The leaf,stem bark and root bark of A.boonei were collected from an open field and air dried before being blended to fine powder.Oils from this plant were extracted by cold extraction and were prepared at different concentrations.Contact toxicity of A.boonei was tested against the larvae and pupae of the insect while smoke toxicity of the plant materials in form of mosquito coil was tested against the adult insect.Results:Alstodine recorded the highest insect mortality rate and the order of susceptibility of the life stages of the insect to the plant was pupae<adult<larvae.Alstodine recorded the highest repellant activity(100%)after 4-5 h of application.However,all the treatments achieved high repellency(above 70%)after 6-7 h of application compared with the control.The formulated mosquito coil(smoke)of A.boonei oil extracts and derivatives showed high rate of protectability as they achieved above 55%protection.Moreover,alstodine(83.22%)showed the greatest smoke toxicity effect on the insect as it recorded almost the same percentage protection as the positive control(Raid synthetic insecticide)which recorded 83.56%protection.Conclusions:This present study has proven A.boonei oil extracts and derivatives as a potential botanical insecticide which could serve as a new thoroughfare of mosquito control.Moreover,the order of effectiveness of the plant can be arranged thus:alstodine>alstonine>stem bark extract>leaf extract>root bark extract.
基金Supported by Bill&Melinda GATES Foundation and the Ministry of Higher Education and Scientific Research of Benin.
文摘Objective:To explore ovariole basal body granulations and follicular dilatations for determining physiological age inAnopheles gambiaes.s.(An.gambiaes.s.).Methods:Mosquitoes were collected by using window trap catch and identified morphologically.For the first lot ofmosquitoes,they were dissected,and ovary was left in distilled water for reading ovarian tracheoles and the second was cut and transferred to another blade in a physiological liquid for verification of ovariole basal body granulations.The same approach was followed with the second lot of mosquitoes where follicular dilatations were found after classic dilaceration of ovaries were transferred into physiological liquid.The other body parts of mosquitoes were used to identify the species of theAn.gambiaes.s.complex by PCR.Results:Among the 123An.gambiae s.s.of the first lot,the method of Detinova determined the age of 89 mosquitoes versus 114 for the observation of granulations(P>0.05).Among the 112An.gambiae s.s.of the second lot,the method of Detinova determined the age of 84 mosquitoes versus 93 for the observation of follicular dilatations(P>0.05).Unlike the method of Detinova,observation of follicular dilatations and basal body granulations of ovarioles were possible beyond the stage II Christophers.Conclusions:Overall,the observation of follicular dilatations and ovariole basal body granulations are reliable for the determination of the physiological age inAn.gambiaes.s.Furthermore,these two methods can be used beyond the stage II.
基金funded by the National Key R&D Program of China(grant number 2020YFC1200101)Perceptive assessment of health risks caused by climate change,air pollution and health co-benefits of low carbon transition in China(grant number 15LCI1)the Emergency Response Mechanism Operation Program,National Institute for Communicable Disease Control and Prevention,Chinese Center for Disease Control and Prevention(grant number 131031102000180007).
文摘Background:Anopheles gambiae(An.gambiae)is considered the most effective malaria vector worldwide and is widely distributed in Africa.The purpose of this study is to determine the potential impact of climate change on An.gambiae and predict the present and future potential suitable habitat globally.Methods:In this study,environmental variables,global occurrence data of An.gambiae,and the maximum entropy model(MaxEnt)were used to evaluate the contribution of environmental factors and predict the habitat suitability of An.gambiae under the current and future scenarios.Results:Among all environmental variables,isothermality(Bio3,34.5%)contributed the most to An.gambiae distribution.Under current climate conditions,the potential suitable areas for An.gambiae are mainly located near the equator(approximately 30°N-30°S),with a total area of 16.58 million km2,including central and northern South America,a fraction of areas near the equator of North America,central and southern Africa,some tropical regions of southern Asia,and small areas of Oceania.The areas of potential suitable habitats would be reduced to varying degrees in future climate scenarios.Conclusions:Potential suitable habitats for An.gambiae may not be limited to Africa.Necessary surveillance and preventive measures should be undertaken in high-risk regions,including those outside Africa,to monitor and control the spread of An.gambiae.
文摘Anopheles funestus and Anopheles gambiae are malaria vector mosquitoes. Knowing their resting behavior is important for implementing control methods. The aim of this study was to investigate the resting behaviour of the two malaria mosquitoes. The study was conducted in Kilombero River Valley and mosquitoes were collected using indoor and outdoor traps from 2012-2015. Poisson mixed models were used to quantify the impact of environment variables on resting behaviour. A log ratio rate between the type of trap and its interaction with environmental variables was used to determine if there was a change over time in the resting behaviour. A total of 4696 mosquitoes were resting indoors of which 57% were A. funestus and 43% were A. gambiae. Similarly, a total of 12,028 mosquitoes were resting outdoor of which 13% were A. funestus and 87% were A. gambiae. Temperature was significant and affected the resting behaviour of A. funestus. Humidity, saturation deficit and temperature were significant variables influencing the resting behaviour of A. gambiae. A. funestus was resting indoor while A. gambiae was resting outdoor over time generally. The findings of this study on the effects of environmental variables and the variations in the resting behaviour of A. gambiae and A. funestus could be used as a guide to implementing appropriate intervention measures such as indoor residential spraying (IRS), insecticide treated nets (ITNs) and mosquito repellents.
