Larvicidal efficacy of crude and fractionated extracts of Dracaena loureiri Gagnep against Aedes aegypti, Aedes albopictus, Culex quinquefasciatus, and Anopheles minimus mosquito vectors

Objective:To evaluate the larvicidal efficacy of crude and fractionated extracts of Dracaena loureiri endocarp against Aedes aegypti,Aedes albopictus,Culex quinquefasciatus,and Anopheles minimus mosquitos.Methods:Larvicidal activity was tested according to World Health Organization standard protocol.The third-stage larvae of each mosquito species were exposed to various concentrations of Dracaena loureiri crude extract and six groups of Dracaena loureiri fractionated extracts(RC-DT 009-014).Larval mortality rates were observed after 24 h and48 h of exposure.Then,a computerized probit analysis of the mortality data was performed to determine lethal concentration 50(LC_(50))and lethal concentration 90 values.Results:Anopheles minimus larvae(24-h LC_(50)77.88 mg/L)had the highest susceptibility to crude extract,whereas others(Aedes aegypti,24-h LC_(50)224.73 mg/L;Aedes albopictus,24-h LC_(50)261.75 mg/L;and Culex quinquefasciatus,24-h LC_(50)282.86 mg/L)were significantly less susceptible.The most effective groups of fractionated extracts were RC-DT 012 and RC-DT 013.The mosquito species most susceptible to fractionated extracts was Culex quinquefasciatus,with 24-h LC_(50)values of 0.66 and 0.94 mg/L for RC-DT 012 and RC-DT 013,respectively.Conclusions:The larvicidal activity of fractionated extracts is more effective than that of crude extract against all tested mosquito species.For the most effective alternative larvicide,purification and a phytochemical constituent analysis must be performed.

Adulticidal, larvicidal, pupicidal and oviposition deterrent activities of essential oil from Zanthoxylum limonella Alston(Rutaceae) against Aedes aegypti(L.) and Culex quinquefasciatus(Say)

Objective: To evaluate adulticidal, larvicidal and oviposition deterrent response of the essential oil from dried Zanthoxylum limonella(Z. limonella) fruit against Aedes aegypti(Ae. aegypti) and Culex quinquefasciatus(Cx. quinquefasciatus).Methods: Z. limonella oil was tested by biological assays at 1%, 5% and 10% concentrations in ethanol. Adulticidal efficacy was tested against the 2–3 day old adult females. Larvicidal activity was tested against immature stage of mosquitoes. Oviposition deterrence of the oil was evaluated on gravid females.Results: The adult mortality was observed after 24 h with the LC50 of 6.0% for Ae.aegypti, and 5.7% for Cx. quinquefasciatus. Larvicidal bioassay was carried out with the 10% Z. limonella oil against immature stages of Ae. aegypti and Cx. quinquefasciatus,which caused 100% mortality after 12 h and 24 h. In the larvicidal experiment,Z. limonella showed effective result at 1%, 5% and 10% concentrations with the values of LT50 Ae. aegypti = 9.78, 5.61, 0.24 h for larvae and LT50= 64.08, 21.23 h for pupae;Cx. quinquefasciatus had LT50= 28.46, 20.25, 1.01 h for larvae and LT50= 67.52, 27.96,4.11 h for pupae, respectively. Oviposition deterrence of the oil was evaluated on gravid females. In the study, 10% Z. limonella showed 100% repellency for Ae. aegypti and99.53% for Cx. quinquefasciatus. Likewise, oviposition activity indexes of these oil concentrations were all negative values ranging from–0.89 to-1.00 for Ae. aegypti and–0.64 to–0.99 for Cx. quinquefasciatus. The oviposition activity indexes values revealed that Z. limonella oil has deterrent effect, and it caused a remarkable negative response resulting in very few eggs.Conclusions: This result indicates that Z. limonella oil can be used as an effective adulticide, larvicide and oviposition deterrent against Ae. aegypti and Cx. quinquefasciatus.

Effectiveness of Some Plant Extracts on the Pupal Stage of Culex Quinquefasciatus （Diptera： Culicidae）

This study aims to evaluate the effectiveness of plant extracts Artemisia herba-alba, Matricharia chamomella, and Melia azedarach against the Culex quinquefasciatus. The following concentrations were used to assess the effectiveness ofA. herba-alba, M. chamomella, and M. azedarach： 0.50, 1.00, 1.50, 2.00, 2.50 and 3.00 mg/L; 0.12, 0.25, 0.50, 0.75, 1.00 and 1.50 mg/L and 0.50, 0.75, 1.00, 1.50, 1.75 and 2.00 mg/L, respectively. The mortality rates of the mosquito pupae were measured after 24 hours. It was found that the LCso was 0.50, 1.00 and 1.80 mg/L of M. chamomile, M. azedarach, and A. herab-alba respectively which mean that M. chamomella extracts had the best pesticide effects against Cx. Quinquefasciatus pupae where was A. herba-alba the lower of them.

Evaluation of Efficacy of Insecticides and Long-Lasting Insecticidal Nets for Control of Culex quinquefasciatus Say Populations from Northern Nigeria

Information on Culex mosquitoes (vectors of filarial worm and viral encephalitis) from northern Nigeria is scanty, hindering evidence-based control. Here, two Culex populations (Kano and Kaduna) were characterized. Culex quinquefasciatus and Culex pipiens were found breeding in sympatry, with some hybrid individuals identified. Larval bioassays revealed high temephos resistance (LC50s = 1.34 mg/mL and 3.01 mg/mL for Kano and Kaduna, respectively). Larvae were more sensitive to α-cypermethrin (LC50s = 0.026 mg/mL and 0.067 mg/mL for Kano and Kaduna). WHO adult tube bioassays revealed high pyrethroid and DDT resistance, with mortalities of 44.01% ± 6.79%, 35.83% ± 12.58%, 29.69% ± 9.97% and 52.47% ± 4.34% for permethrin, deltamethrin, α-cypermethrin and DDT, respectively. Highest resistance was observed with bendiocarb (mortality = 13.58% ± 3.98%). High resistance was obtained with fenitrothion and malathion (mortalities = 21% ± 4.76% and 56.47% ± 8.67%, respectively), while a full susceptibility was observed with pirimiphos-methyl. Pre-exposure to piperonylbutoxide (PBO) significantly recovered α-cypermethrin susceptibility (mortality = 82% ± 5.16%, χ2 = 50.99, p < 0.0001), compared with the conventional bioassay (mortality = 32 ± 7.30). Mortalities of <20% were obtained in cone bioassays with Yorkool, DuraNet and PermaNet3.0 (side panels) nets, suggesting a loss of efficacy of conventional long-lasting insecticidal nets. However, mortalities of 99% and 86% were obtained in Kano and Kaduna populations using the roof of PermaNet3.0 (containing PBO and deltamethrin). Despite the high frequency of the 1014F VGSC knockdown resistance mutation allele (0.90), no correlation was observed between the 1014F kdr genotype and resistance phenotype. Sequencing of fragments of the acetylcholinesterase-1 gene detected no G119S mutation, in malathion-alive and malathion-dead females. These suggest a preeminent role of metabolic resistance in these Culex populations.

Adjusting Second Moment Bias in Eigenspace Using Bayesian Empirical Estimators, Dirichlet Tessellations and Worldview I Data for Predicting Culex Quinquefasciatus Habitats in Trinidad

Temporally weighted regression models with a spatial autoregressive component may estimate nonlinearities in spatiotemporal-sampled data of Culex quinquefasciatus, a major vector of West Nile Virus (WNV) which can help implement control strategies by determining optimal predictors associated to prolific habitats. The design of this kind of mixed model can specifically incorporate spatial autocorrelation whilst including the influence of other aspatial predictor variables. Currently, the lack of an estimation theory that allows for het- eroscedasticity and corresponding joint hypothesis testing in the presence of spatial dependence in georefer- enced Cx. quinquefasciatus habitat data is a serious shortcoming in WNV research. In this paper we used spatially lagged and simultaneous autoregressive models based on multiple predictor variables of immature Cx. quinquefasciatus and Worldview 1 (WV-1) data to help implant a remote habitat-based surveillance sys- tem in Trinidad. Initially, we used Geomatica Ortho Engine? v. 10.2 for extracting a Digital Elevation Model (DEM) from the WV-1 raw imagery. Results of the DEM analyses indicated a statistically significant inverse linear relationship between total sampled Cx. quinquefasciatus data and elevation (m) (R2 = -0.439;p < 0.0001), with a standard deviation of 10.41. Additional field-sampled information was derived using data from an or-thogonal grid-matrix constructed in an ArcInfo 9.3? and overlaid onto the WV-1 data. A unique identifier was placed in the centroid of each grid cell. Univariate statistics and Poisson regression models were then generated using the georeferenced covariates in SAS/GIS?. Coefficient estimates were also used to define expectations for prior distributions in a Bayesian estimation matrix using Markov Chain Monte Carlo (MCMC) specifications. A spatial residual trend analyses was then performed using autocorrelation indices which linked tabular data in SAS PROCLMIXED? with the egg-raft count data in ArcInfo?. The estimation matrix identified prolific habitats based on the covariate distance to the nearest house. An Ordinary kriged-based interpolator was then constructed in Geostatistical Analyst Extension of ArcGIS 9.3? based on the adjusted Bayesian estimates. For total Cx. quinquefasciatus egg-raft count, first order trend was fitted to the semivariogram at a partial sill of 5.931 km, nugget of 6.374 km, lag size of 7.184 km, and a range of 31.02 km using 12 lags. We assessed the performance accuracy of the interpolation procedures based on the magnitude and distribution of errors between observed and model-predicted values using Voroni tessella- tions. These residuals divided the space between the individual georeferenced Cx. quinquefasciatus habitats by XY coordinates in 2-dimenisional space which revealed that the geophysical parameter error residuals in the interpolation model were within normal statistical limitations. Newer GIS software and WV-1 data can generate highly accurate predictive Cx. quinquefasciatus habitat distribution models which can target prolific habitats of based on field-sampled count data. Our results suggest it may be unnecessary to manage all Cx. quinquefasciatus habitats to obtain significant reductions in incidence and prevalence of WNV in Trinidad.

The infection kinetics and transmission potential of two Guaico Culex viruses in Culex quinquefasciatus mosquitoes

Guaico Culex virus(GCXV)is a newly identified segmented Jingmenvirus from Culex spp.mosquitoes in Central and South America.The genome of GCXV is composed of four or five single-stranded positive RNA segments.However,the infection kinetics and transmission capability of GCXV in mosquitoes remain unknown.In this study,we used reverse genetics to rescue two GCXVs(4S and 5S)that contained four and five RNA segments,respectively,in C6/36 cells.Further in vitro characterization revealed that the two GCXVs exhibited comparable replication kinetics,protein expression and viral titers.Importantly,GCXV RNAs were detected in the bodies,salivary glands,midguts and ovaries of Culex quinquefasciatus at 4–10 days after oral infection.In addition,two GCXVs can colonize Cx.quinquefasciatus eggs,resulting in positive rates of 15%–35%for the second gonotrophic cycle.In conclusion,our results demonstrated that GCXVs with four or five RNA segments can be detected in Cx.quinquefasciatus eggs during the first and second gonotrophic cycles after oral infection.

Molecular and functional characterization of three novel carboxylesterases in the detoxification of permethrin in the mosquito, Culex quinquefasciatus

Carboxylesterases (CarEs) belong to a super family of multifunctional enzymes associated with the degradation of endogenous and exogenous compounds. Many insect CarEs are known to play important roles in catalyzing the hydrolysis of organophosphates (OPs), carbamates, and synthetic pyrethroids (SPs). The elevation of esterase activity through gene amplification and overexpression of estα2 and estβ2 genes contributes to the development of resistance to OP insecticides in the mosquito Culex quinquefasciatus. Three additional CarE genes are upregulated in permethrin-resistant Cx. quinquefasciatus according to an RNA-seq analysis, but their function remains unknown. In this study, we, for the first time, characterized the function of these three novel genes using in vitro protein expression, an insecticide metabolism study and molecular docking analysis. All three CarE genes were significantly overexpressed in resistant mosquito larvae, but not adults, compared to susceptible strain. No gene copy differences in these three genes were found in the mosquitoes tested. In vitro high-performance liquid chromatography (HPLC) revealed that CPIJ018231, CPIJ018232, and CPIJ018233 metabolized 30.4% ± 2.9%, 34.7% ± 6.8%, and 23.2% ± 2.2% of the permethrin, respectively. No mutations in resistant strains might significantly affect their CarE hydrolysis ability. A docking analysis further confirmed that these three CarEs from resistant strain all potentially metabolize permethrin. Taken together, these three carboxylesterase genes could play important roles in the development of permethrin resistance in Cx. quinquefasciatus larvae through transcriptional overexpression, metabolism, and detoxification.

Three-dimensional structure of the antennal lobe in the Southern house mosquito Culex quinquefasciatus

The Southern house mosquito Culex quinquefasciatus relies on its olfactory system to locate the human hosts for blood meals,by which several deadly diseases are transmitted.Olfactory sensory neurons(OSNs)housed in the sensilla on the olfactory appendages send their axons into the antennal lobes(ALs),the primary olfactory center in the brain,where the OSNs expressing the same olfactory receptors converge upon the same spherical structures known as glomeruli in the AL.The structure of the antennal lobe,that is,the spatial organization of the glomeruli,governs the insect's odor identification and discrimination.Drosophila studies have demonstrated the specific connections between receptors and glomeruli based on the 3D structure of the antennal lobe,deepening our understanding of the relationships between glomerular activities and behaviors,but as yet the structure of the Cx.quinquefasciatus antennal lobe remains unknown.We therefore constructed a 3D model of the Cx.quinquefasciatus antennal lobe using nc82 antibody staining,identifying 62 and 44 glomeruli in the female and male mosquito antennal lobe,respectively,with a significant sexual dimorphism in terms of the antennal lobe volume and glomerulus number.These results demonstrate the structural basis of mosquito odor coding and provide a platform for future studies of the mosquito olfactory signal processing mechanism.

Identification and characterization of long noncoding RNAs and their association with acquisition of blood meal in Culex quinquefasciatus

The Southern house mosquito,Culex quinquefasciatus(Cx.quinquefasciatus)is an important vector that transmit multiple diseases including West Nile encephalitis,Japanese encephalitis,St.Louis encephalitis and lymphatic filariasis.Long noncoding RNAs(lncRNAs)involve in many biological processes such as development,infection,and virus–host interaction.However,there is no systematic identification and characterization of lncRNAs in Cx.quinquefasciatus.Here,we report the first lncRNA identification in Cx.quinquefasciatus.By using 31 public RNA-seq datasets,a total of 4763 novel lncRNA transcripts were identified,of which 3591,569,and 603 were intergenic,intronic,and antisense respectively.Examination of genomic features revealed that Cx.quinquefasciatus shared similar characteristics with other species such as short in length,low GC content,low sequence conservation,and low coding potential.Furthermore,compared to protein-coding genes,Cx.quinquefasciatus lncRNAs had lower expression values,and tended to be expressed in temporally specific fashion.In addition,weighted correlation network and functional annotation analyses showed that lncRNAs may have roles in blood meal acquisition of adult female Cx.quinquefasciatus mosquitoes.This study presents the first systematic identification and analysis of Cx.quinquefasciatus lncRNAs and their association with blood feeding.Results generated from this study will facilitate future investigation on the function of Cx.quinquefasciatus lncRNAs.

Lymphatic filariasis, infection status in Culex quinquefasciatus and Anopheles species after six rounds of mass drug administration in Masasi District, Tanzania

Background:Lymphatic filariasis(LF)elimination program in Tanzania started in 2000 in response to the Global program for the elimination of LF by 2020.Evidence shows a persistent LF transmission despite more than a decade of mass drug administration(MDA).It is advocated that,regular monitoring should be conducted in endemic areas to evaluate the progress towards elimination and detect resurgence of the disease timely.This study was therefore designed to assess the status of Wuchererio bancrofti infection in Culex quinqefasciatus and Anopheles species after six rounds of MDA in Masasi District,South Eastern Tanzania.

Mosquito larvicidal properties of Impatiens balsamina(Balsaminaceae)against Anopheles stephensi,Aedes aegypti and Culex quinquefasciatus(Diptera:Culicidae)

Objective:To assess the larvicidal potential of the crude benzene,chloroform,ethyl acetate and methanol solvent extracts of the medicinal plant Impatiens balsamina against Anopheles stephensi(An.stephensi),Aedes aegypti(Ae.aegypti)and Culex quinquefasciatus(Cx.quinquefasciatus).Methods:Twenty five third instar larvae of An.stephensi,Ae.aegypti and Cx.quinquefasciatus were exposed to various concentrations and were assayed in the laboratory by using the protocol recommended by WHO.The larval mortality was observed after 24 h of treatment.Results:Among extracts tested,the highest larvicidal activity was observed in leaf methanol extract of Impatiens balsamina against An.stephensi,Ae.aegypti and Cx.quinquefasciatus with the LC_(50)and LC_(90)values 98.04,119.68,125.06 and 172.93,210.14,220.60 mg/L,respectively.Conclusions:From the results it can be concluded that the larvicidal effect of Impatiens balsamina against An.stephensi,Ae.aegypti and Cx.quinquefasciatus make this plant product promising as an alternative to synthetic insecticide in mosquito control programs.

Influence of light and habitat on predation of Culex quinquefasciatus （Diptera： Culicidae）larvae by the waterbugs （Hemiptera： Heteroptera）

The influence of light and habitat structure on the predation of Culex quinquefasciatus larvae by the common heteropteran water bug, Diplonychus （= Sphaerodema） annulatus, D. rusticus and Anisops bouvieri was assessed in the laboratory. It was revealed that water bugs predate more in presence of light than in dark conditions. While A. bouvieri consumed more prey in structured conditions, D. annulatus and D. rusticus consumed more prey in open conditions. The selection of prey size as well as the respective numbers varied between predators and treatments significantly. Prey vulnerability （PV）, an indicator of predatory efficiency, was highest for D. annulatus, moderate for D. rusticus and low for A. bouvieri. Prey consumption and PV values under different treatment conditions indicate that for belostomatid water bugs D. annulatus and D. rusticus, the order of prey consumption under different habitat and light/dark combinations is light open 〉 dark open 〉 light vegetated 〉 dark vegetated. In the case of the backswimmer, A. bouvieri, the order of prey consumption appeared to be light structured 〉 dark structured 〉 light open 〉 dark open. These findings were consistent with resource-partitioning by water bug species sharing the same guild. If the observed results are extended to natural settings the efficiency of these predators in controlling mosquito populations will vary with the structural complexity of habitats and the intensity of light.

Permethrin resistance variation and susceptible reference line isolation in a field population of the mosquito, Culex quinquefasciatus （Diptera： Culicidae）

This study examines the genetic variations and mechanisms involved in the development of permethrin resistance in individual mosquitoes from a field population of Culex quinquefasciatus, HAmCq^G0, and characterizes susceptible reference lines of mosquitoes with a similar genetic background to the field HAmCq^G0 strain. Six upregulated cytochrome P450 genes, CYP9M10, CYP9J34, CYP6P14, CYP9J40, CYP6AA7, and CYP4C52v1, previously identified as being upregulated in the larvae of resistant HAmCq68 mosquitoes were examined in the larvae of 3 strains （susceptible S-Lab, parental HAmCq^G0 and permethrin-selected highly resistant HAmCq68） and 8 HAmCq^G0 single- egg raft colonies, covering a range of levels of susceptibility/resistance to perrnethrin and exhibiting different variations in the expression of A and/or T alleles at the L-to-F kdr locus of the sodium channel. The 2 lines with the lowest tolerance to permethrin and bearing solely the susceptible A allele at the L-to-F kdr locus of the sodium channels, from colonies Cx_SERC5 and Cx_SERC8, showed lower or similar levels of all 6 of the P450 genes tested compared with the S-Lab strain, suggesting that these 2 lines could be used as the reference mosquitoes in future studies characterizing insecticide resistance in HAmCq mosquitoes. This study also provides a detailed investigation of the mechanisms involved in insecticide resistance in individuals within a population： individuals with elevated levels of resistance to permethrin all displayed one or more potential resistance mechanisms-either elevated levels of P450 gene expression, or L-to-F mutations in the sodium channel, or both.

First report of L1014F kdr mutation in Culex quinquefasciatus in Mexico

The L1014F mutation in the voltage-sodium channel gene has been associated with resistance to DDT and pyrethroids in various arthropod species including mosquitoes. We determined the frequency of the L1014F kdr mutation in 16 field populations of Culex quinquefasciatus from Northeastern Mexico collected between 2008 and 2013. The L1014F was present in all populations analyzed with the lowest frequency （3.33%） corresponding to the population from Monclova collected in 2012, and the highest frequency （63.63%） from the Monterrey population collected in 2012. The presence of a kdr mutation in populations of Cx. quinquefasciatus from northeastern Mexico provides evidence ofpyrethroid resistance. This requires a special attention, considering that pyrethroid-based insecticides are commonly used in vector-control campaigns, especially against Aedes aegypti （L.）.

Evaluation of water and ethanol extracts of Schinus molle Linn.against immature Culex quinquefasciatus Say(Diptera:Culicidae)

Objective:To evaluate larvicidal and pupicidal activities of aqueous and ethanol extract of different parts of Schinus molle against filarial vector,Culex quinquefasciatus(Cx.quinquefasciatus)in the laboratory.Methods:The mortality rate of third,fourth instar larvae and pupal stages were tested at 20,40,60,80 and 100 mg/L of plant extract using WHO standard protocol with modifications.The mortality rate was recorded continuously for 24,48 and 72 h post exposure period and percentage mortality was calculated.Results:Maximum percentage mortality of third instar was 83.3%in ethanol extract of mature fruit at 100 mg/L after 24 h exposure period.After 48 h exposure period,93.3%percentage mortality was recorded in ethanol extract of immature fruit at 100 mg/L.After 72 h exposure period,100%mortality was recorded in water extract of leaf at 100 mg/L.In fourth instar larvae,maximum percentage mortality of 63.3%was recorded in water extract of mature fruit and ethanol extract of immature and mature fruit at 100 mg/L after 24 h exposure period.After 48 h exposure period 86.6%mortality was recorded in ethanol extract of mature fruit at 100 mg/L.After 72 h exposure period,93.3%mortality was recorded in ethanol extract of mature fruit at 100 mg/L.In general immature Cx.quinquefasciatus,percentage mortality was increased with increase in exposure time and concentration of the plant extracts tested.Conclusions:From this laboratory study,Schinus molle plant parts were proved to have larvicidal and pupicidal activity against immature Cx.quinquefasciatus.

Adulticidal efficacy of Delonix elata against filariasis vector mosquito,Culex quinquefasciatus(Diptera:Culicidae)

Objective:To evaluate the adulticidal activity and toxicity of different solvent crude extracts of Delonix elata(D.elata)against filariasis vector mosquito Culex quinquefasciatus(Cx.quinquefasciatus).Methods:The adulticidal activities of crude hexane,benzene,ethyl acetate,chloroform and methanol leaf and seed extracts of D.elata were assayed for their toxicity against vector mosquitoCx.quinquefasciatus.Bioassay was carried out by WHO method for determination of adulticidal activity against mosquitoes.The adult mortality was observed after 24 h of exposure.Results:All extracts showed moderate adulticidal effects;however,the highest adult mortality was found in methanol extract of D.elata leaf against the adults of Cx.quinquefasciatus with the LC_(50) and LC_(90) values at 197.28 and 347.45mg/L,respectively.Conclusions:These results suggest that the leaf solvent plant extracts have the potential to be used as an ideal eco-friendly approach for the control of mosquitoes.This study provides first report on the mosquito adulticidal activity of D.elata plant extracts against filariasis vector mosquito,Cx.quinquefasciatus.

Mosquito larvicidal and ovicidal properties of Pithecellobium dulce(Roxb.)Benth.(Fabaceae)against Culex quinquefasciatus Say(Diptera:Culicidae)

Objective:To assess the larvicidal and ovicidal potential of the crude hexane,benzene,chloroform,ethyl acetate and methanol solvent extracts from the medicinal plant,Pithecellobium dulce(P.dulce)against filariasis vector mosquito,Culex quinquefasciatus(Cx.quinquefasciatus).Methods:Twenty five early third instar larvae of Cx.quinquefasciatus were exposed to various concentrations and were assayed in the laboratory by using the protocol of W HO(2005).The larval mortality was observed after 24 h of treatment.The ovicidal activity was determined against Cx.quinquefasciatus mosquito eggs to various concentrations ranging from 100-750 mg/L under the laboratory conditions.Results:The methanol extract of the leaves and seed of P.dulce was the most effective against the larvae with LCs0 and LCgo values 164.12 mg/L,214.29 mg/L,289.34 mg/L and 410.18 mg/L being observed after 24 h of exposure.The efficacy of methanol was followed by that of the ethyl acetate,chloroform,benzene and hexane extracts.The mean percent hatchability of the egg rafts were observed after 48 h of treatment.About 100%mortality was observed at 500 mg/L for leaf and 750 mg/L for seed methanol extracts of P.dulce.Conclusions:From the results,it can be concluded that the larvicidal and ovicidal effect of P.dulce against Cx.quinquefasciatus make this plant product promising as an alternative to synthetic insecticide in mosquito control programs.

The Influence of Portulaca Oleracea L. Leaves Extracts on the Histoarchitecture of Culex Quinquefasciatus and Anopheles Stephensi Larvae

Background:Mosquito is a big threat to the human health.Mosquito-borne diseases cause millions of death to the human beings.Hence,a permanent solution is eagerly to be established to control its excessive growth in stagnant water.Portulaca oleracea Linn is a natural larvicidal agent,which contains active ingredients such as linolenic acid,linoleic acid(omega-3 fatty acids).These bioactive compounds may be responsible for its larvicidal properties on mosquito.Objective:The present study is focussed on identifying the bioactive compounds,such as linolenic acid,through GC-MS,and analyzing the larvicidal efficacy of Portulaca oleracea L.against Culex quinquefasciatus and Anopheles stephensi larvae.Methods:Preliminary phytochemical analysis,total protein content,total carbohydrate content,total phenol content,total flavonoid content and GC-MS analysis exhibited the presence of rich phytoconstituents in Portulaca oleracea.DPPH analysis was carried out to analyze the antioxidant potential of plant extract.Larvicidal activity and histological change were detected to evaluate the efficacy of Portulaca oleracea L.on the Culex quinquefasciatus and Anopheles stephensi larvae.Results:Aqueous and ethanol leaf extracts of Portulaca oleracea L.against both Culex quinquefasciatus and Anophe-les stephensi larvae,showed a very good larvicidal activity at 500μg/mL among the various concentrations.His-tological damages of mosquito larvae were observed when treated with the Portulaca oleracea L.extract,and provided further evidence for its larvicidal activity.Conclusion:This study concluded that the plant Portulaca oleracea L.contained many useful bioactive compounds,can be a strong larvicidal agent against both Culex quinquefasciatus and Anopheles stephensi larvae.The molecular mechanism for the larvicidal activity will be identified in future studies.

Mutations and intron polymorphisms in voltage-gated sodium channel genes of different geographic populations of Culex pipiens pallens/Culex pipiens quinquefasciatus in China

Background Culex pipiens pallens and Culex pipiens quinquefasciatus are the dominant species of Culex mosquitoes in China and important disease vectors.Long-term use of insecticides can cause mutations in the voltage-gated sodium channel(vgsc)gene of mosquitoes,but little is known about the current status and evolutionary origins of vgsc gene in different geographic populations.Therefore,this study aimed to determine the current status of vgsc genes in Cx.p.pallens and Cx.p.quinquefasciatus in China and to investigate the evolutionary inheritance of neighboring downstream introns of the vgsc gene to determine the impact of insecticides on long-term evolution.Methods Sampling was conducted from July to September 2021 in representative habitats of 22 provincial-level administrative divisions in China.Genomic DNA was extracted from 1308 mosquitoes,the IIS6 fragment of the vgsc gene on the nerve cell membrane was amplified using polymerase chain reaction,and the sequence was used to evaluate allele frequency and knockdown resistance(kdr)frequency.MEGA 11 was used to construct neighborjoining(NJ)tree.PopART was used to build a TCS network.Results There were 6 alleles and 6 genotypes at the L1014 locus,which included the wild-type alleles TTA/L and CTA/L and the mutant alleles TTT/F,TTC/F,TCT/S and TCA/S.The geographic populations with a kdr frequency less than 20.00%were mainly concentrated in the regions north of 38°N,and the geographic populations with a kdr frequency greater than 80.00%were concentrated in the regions south of 30°N.kdr frequency increased with decreasing latitude.And within the same latitude,the frequency of kdr in large cities is relatively high.Mutations were correlated with the number of introns.The mutant allele TCA/S has only one intron,the mutant allele TTT/F has three introns,and the wild-type allele TTA/L has 17 introns.Conclusions Cx.p.pallens and Cx.p.quinquefasciatus have developed resistance to insecticides in most regions of China.The neighboring downstream introns of the vgsc gene gradually decreased to one intron with the mutation of the vgsc gene.Mutations may originate from multiple mutation events rather than from a single origin,and populations lacking mutations may be genetically isolated.

Adsorption of Toxic Metals and Control of Mosquitos-borne Disease by Lysinibacillus sphaericus:Dual Benefits for Health and Environment

Objective Assessment of the bacterium L. sphaericus as a dual-action candidate for biological control of mosquito-borne diseases and bioremediation of toxic metals. Methods Larvae of the mosquito, C quinquefasciatus, were first evaluated for metal tolerance and then exposed to 5 ppm cadmium, chromium, arsenic, and lead in assays together with seven strains of L. sphaericus. A probit regression analysis was used to estimate the LCso of Cd, Cr, As, and Pb to C. quinquefosciatus. An analysis of covariance and multifactorial ANOVA examined the metal biosorption and larvicidal properties of the seven strains of L. sphaericus. Results We found that L. sphaericus adsorbed the toxic metal ions and was toxic against mosquito larvae. The L. sphoericus strain 111（3）7 resulted in a larvae mortality of over 80% for all the tested metals. This strain also exhibited the capacity to adsorb 76% of arsenic, 32% of lead, 25% of chromium, and 7% of cadmium. Conclusion This study found combined metal adsorption and larval toxicity associated with three strains of L. sphaericus [111（3）7, OT4b.31, and CBAM5]. This suggests that a combination of these strains shows strong dual potential for biological control of mosquitos in heavy metal-contaminated areas and remediate the heavy metal contamination as well.