Aegypti Adults Research Articles

Expression Pattern and RNAi Inhibition of Putative Sodium‐coupled Cation‐chloride Cotransporters in the Mosquito Aedes aegypti

The mosquito Aedes aegypti possesses three genes with sequence similarity to sodium-coupled cation-chloride cotransporters (CCCs). We began to characterize these genes through phylogenetic analysis, assessment of tissue distribution, and preliminary RNAi experiments. The protein predicted by VectorBase AAEL006180 (tentatively named aeCCC1) groups with Drosophila melanogaster Na-K-Cl cotransporter dmNCC69 (CG4357) and mammalian Na-K-Cl and Na-Cl cotransporters, whereas proteins predicted by AAEL009888 (aeCCC2) and AAEL009886 (aeCCC3) group with Manduca sexta msBSC and Drosophila CG31457. We evaluated expression of aeCCC1, aeCCC2, and aeCCC3 in tissues of Ae. aegypti larvae and adults. For aeCCC1 and aeCCC2, expression was similar between adults and larvae. In contrast, aeCCC3 was ~500-fold more abundant in larvae compared to adults. In adult female mosquitoes, aeCCC1 was most highly expressed in head and Malpighian tubules whereas aeCCC2 was most highly expressed in hindgut. In larvae, aeCCC3 was 6000-fold more abundant in anal papillae compared to Malpighian tubules. To begin assessing aeCCC1 function, we used RNAi to knock down its expression. We generated two ~500 bp dsRNAs, injected them into adult female mosquitoes, and assessed aeCCC mRNA expression 4 days after injection. Both dsRNAs reduced aeCCC1 expression compared to control mosquitoes injected with PBS. Changes in aeCCC2 and aeCCC3 expression were also detected, suggesting either direct or indirect off-target effects. Our findings suggest that the Aedes aegypti CCCs may play distinct roles in mosquito osmoregulation.

Evaluation of AaDOP2 receptor antagonists reveals antidepressants and antipsychotics as novel lead molecules for control of the yellow fever mosquito, Aedes aegypti.

The yellow fever mosquito, Aedes aegypti, vectors disease-causing agents that adversely affect human health, most notably the viruses causing dengue and yellow fever. The efficacy of current mosquito control programs is challenged by the emergence of insecticide-resistant mosquito populations, suggesting an urgent need for the development of chemical insecticides with new mechanisms of action. One recently identified potential insecticide target is the A. aegypti D1-like dopamine receptor, AaDOP2. The focus of the present study was to evaluate AaDOP2 antagonism both in vitro and in vivo using assay technologies with increased throughput. The in vitro assays revealed AaDOP2 antagonism by four distinct chemical scaffolds from tricyclic antidepressant or antipsychotic chemical classes, and elucidated several structure-activity relationship trends that contributed to enhanced antagonist potency, including lipophilicity, halide substitution on the tricyclic core, and conformational rigidity. Six compounds displayed previously unparalleled potency for in vitro AaDOP2 antagonism, and among these, asenapine, methiothepin, and cis-(Z)-flupenthixol displayed subnanomolar IC50 values and caused rapid toxicity to A. aegypti larvae and/or adults in vivo. Our study revealed a significant correlation between in vitro potency for AaDOP2 antagonism and in vivo toxicity, suggesting viability of AaDOP2 as an insecticidal target. Taken together, this study expanded the repertoire of known AaDOP2 antagonists, enhanced our understanding of AaDOP2 pharmacology, provided further support for rational targeting of AaDOP2, and demonstrated the utility of efficiency-enhancing in vitro and in vivo assay technologies within our genome-to-lead pipeline for the discovery of next-generation insecticides.

Insecticide resistance and its underlying mechanisms in field populations of Aedes aegypti adults (Diptera: Culicidae) in Singapore.

BackgroundIn Singapore, dose–response bioassays of Aedes aegypti (L.) adults have been conducted, but the mechanisms underlying resistance to insecticides remain unclear. In this study, we evaluated insecticide resistance and its underlying mechanism in field populations of Ae. aegypti adults.MethodsSeven populations of Ae. aegypti were collected from public residential areas and assays were conducted according to WHO guidelines to determine their susceptibility to several commonly used insecticides.ResultsVarious levels of pyrethroid resistance (RR50 = 3.76 to 142.06-fold) and low levels of pirimiphos-methyl resistance (RR50 = 1.01 to 1.51-fold) were detected. The insecticide susceptibility profile of Ae. aegypti adults was homogenous among the different study sites. Addition of the synergists piperonyl butoxide, S,S,S,-tributyl phosphorotrithioate, and triphenyl phosphate generally failed to enhance the toxicity of the insecticides investigated, suggesting an insignificant role of metabolic-based insecticide resistance and possible involvement of target site resistance. Further biochemical investigation of specific metabolic enzyme activities provided further evidence that detoxifying enzymes such as mono-oxygenases, esterases, glutathione S-transferases and altered acethylcholinesterases generally did not contribute to the resistance observed.ConclusionsThis study confirmed the presence of pyrethroid resistance among Ae. aegypti adults in Singapore and documented the early onset of organophosphate resistance.

Intra-annual changes in abundance of Aedes (Stegomyia) aegypti and Aedes (Ochlerotatus) epactius (Diptera: Culicidae) in high-elevation communities in Mexico.

We examined temporal changes in the abundance of the mosquitoes Aedes (Stegomyia) aegypti (L.) and Aedes (Ochlerotatus) epactius Dyar & Knab from June to October 2012 in one reference community at lower elevation (Rio Blanco; approximately 1,270 m) and three high-elevation communities (Acultzingo, Maltrata, and Puebla City; 1,670-2,150 m) in Veracruz and Puebla States, México. The combination of surveys for pupae in water-filled containers and trapping of adults, using BG-Sentinel traps baited with the BG-Lure, corroborated previous data from 2011 showing that Ae. aegypti is present at low abundance up to 2,150 m in this part of México. Data for Ae. aegypti adults captured through repeated trapping in fixed sites in Acultzingo--the highest elevation community (approximately 1,670 m) from which the temporal intra-annual abundance pattern for Ae. aegypti has been described--showed a gradual increase from low numbers in June to a peak occurrence in late August, and thereafter declining numbers in September. Ae. epactius adults were collected repeatedly in BG-Sentinel traps in all four study communities; this is the first recorded collection of this species with a trap aiming specifically to collect human-biting mosquitoes. We also present the first description of the temporal abundance pattern for Ae. epactius across an elevation gradient: peak abundance was reached in mid-July in the lowest elevation community (Rio Blanco) but not until mid-September in the highest elevation one (Puebla City). Finally, we present data for meteorological conditions (mean temperature and rainfall) in the examined communities during the study period, and for a cumulative measure of the abundance of adults over the full sampling period.

Natural vertical transmission of dengue-1 virus in Aedes aegypti populations in Acapulco, Mexico.

We carried out dengue virus surveillance in Aedes aegypti populations from 47 neighborhoods of Acapulco during the rainy season of 2011 following a standard national protocol and as an improvement of the entomological surveillance of the Mexican Dengue Control Program. A total of 4,146 Ae. aegypti adults collected indoors and/or emerged from eggs, larvae, or pupae from households with dengue reports (probable or confirmed cases), were grouped into pools and processed using a standardized serotype-specific 4-plex real-time reverse transcriptase-polymerase chain reaction assay. Overall, only 2 (0.9%) of 226 pools of Ae. aegypti adults (1 pool of adults emerged from field-collected larvae, and another of indoor-collected adults) were positive for dengue virus 1 (DENV-1). This is appears to be the 1st report of evidence on the vertical and transovarial transmission of DENV-1 in field-caught Ae. aegypti in Mexico.

Evaluation of Moringa oleifera seed lectin in traps for the capture of Aedes aegypti eggs and adults under semi-field conditions

The water-soluble lectin isolated from Moringa oleifera seeds (WSMoL) is a larvicidal, ovicidal, and oviposition-stimulating agent against Aedes aegypti under laboratory conditions. This study investigated the effect of WSMoL in traps for the capture of A. aegypti eggs and adult females under semi-field conditions and determined whether gravid females could detect WSMoL by an olfactory response. WSMoL was isolated according to a previously described procedure using chitin chromatography. The bioassays were performed in large cages (12.5 m(3)). Two traps for collection of eggs (ovitrap) or adult mosquitoes (MosquiTRAP(TM)) were placed in a cage. One was filled with WSMoL (0.1 mg/mL) and the other with tap water (negative control). An infusion of Panicum maximum leaves was used as a positive control. Forty gravid females were then released in each cage. After 2 (for oviposition) or 3 h (for female capture), the traps were removed, and the number of eggs or females was counted. An olfactometry assay was performed to investigate whether the effect of WSMoL on gravid females was linked to an olfactory response. WSMoL showed an oviposition-stimulating effect (65 ± 14%) that was similar (p < 0.05) to that promoted by the P. maximum infusion (67 ± 11%). The efficiency of MosquiTRAP(TM) in capturing gravid females was not increased by WSMoL. The olfactometry assay indicated that the response of females to WSMoL did not involve the stimulation of olfactory sensilla. WSMoL effectively captured eggs when used in ovitraps under semi-field conditions; this property, together with the ovicidal and larvicidal activities of this lectin, makes it an interesting candidate for A. aegypti control.

Insecticide resistance and its underlying mechanisms in field populations of Aedes aegypti adults (Diptera: Culicidae) in Singapore

In Singapore, dose–response bioassays of Aedes aegypti (L.) adults have been conducted, but the mechanisms underlying resistance to insecticides remain unclear. In this study, we evaluated insecticide resistance and its underlying mechanism in field populations of Ae. aegypti adults. Seven populations of Ae. aegypti were collected from public residential areas and assays were conducted according to WHO guidelines to determine their susceptibility to several commonly used insecticides. Various levels of pyrethroid resistance (RR50 = 3.76 to 142.06-fold) and low levels of pirimiphos-methyl resistance (RR50 = 1.01 to 1.51-fold) were detected. The insecticide susceptibility profile of Ae. aegypti adults was homogenous among the different study sites. Addition of the synergists piperonyl butoxide, S,S,S,-tributyl phosphorotrithioate, and triphenyl phosphate generally failed to enhance the toxicity of the insecticides investigated, suggesting an insignificant role of metabolic-based insecticide resistance and possible involvement of target site resistance. Further biochemical investigation of specific metabolic enzyme activities provided further evidence that detoxifying enzymes such as mono-oxygenases, esterases, glutathione S-transferases and altered acethylcholinesterases generally did not contribute to the resistance observed. This study confirmed the presence of pyrethroid resistance among Ae. aegypti adults in Singapore and documented the early onset of organophosphate resistance.

Occurrence of Aedes aegypti (Diptera, Culicidae) in a Dengue Transmission Area at Coastal Maranhão State, Brazil

This study aimed to estimate the occurrence of Aedes aegypti adults at distinct climatic seasons at neighbor- hoods from the municipality of Sao Luis, Maranhao State, Brazil, as well as to verify the presence of Dengue virus (DENV) in the specimens collected. A total of 320 properties were visited in eight neighborhoods that were previously randomly chosen. Samplings were made at three periods: dry season/2008, rainy season/2009 and dry season/2009. A to- tal of 563 Ae. aegypti mosquitoes were collected, with 141 of them collected during dry season/2008, 272 during rainy season/2009 and the remnant, during dry season/2009. Specimen were divided into lots and subjected to RT-semi-nested- PCR analysis and virus isolation was carried out using cell culture (C6/36 clone) of Ae. albopictus. The number of adults significantly varied at the neighborhoods of Coreia de Baixo, Lira, Joao Paulo, and Conjunto Cohatrac I. Molecular anal- yses of specimens showed no positivity for DENV. At the municipality of Sao Luis, seasonal climate variation might in- fluence the density of Ae. aegypti adults, however, other factors such as population density, sanitation conditions, and the presence of mosquito breeding sites ought to be assessed as important parameters influencing vector dispersion.

Effect of culture medium on the production and virulence of submerged spores of Metarhizium anisopliae and Beauveria bassiana against larvae and adults of Aedes aegypti (Diptera: Culicidae)

Three Metarhizium anisopliae and three Beauveria bassiana isolates were cultivated in media containing casamino acids, soybean flour or sunflower seed flour and were shaken for three days. M. anisopliae presented similar yields of around 106 submerged spores/ml without significant differences among them, whereas B. bassiana produced yields of around 108 spores/ml, of which GHA strain produced more submerged spores in the casamino acids medium. The other two strains showed no significant difference in the production of submerged spores in the three media used. Differences in mortality on Aedes aegypti larvae were observed with the submerged spores of Metarhizium depending on isolate and medium used. M. anisopliae 2157 caused significantly higher mortality (40%) when cultivated in casamino acids medium. It presented an LC50 of 8.93 × 105 submerged spores/ml water against mosquito larvae five days after application, whereas it caused 27% mortality in Ae. aegypti adults 10 days after application. In conclusion, fungal nutrition affected virulence of some isolates of M. anisopliae against Ae. aegypti larvae while such an effect was not noted for B. bassiana isolates.

Aedes aegyptiMosquitoes at Nonresidential Sites Might be Related to Transmission of Dengue Virus in Monterrey, Northeastern Mexico

Traditionally the major risk environment for transmission of dengue virus has been assumed to be households. In Mexico, dengue outbreaks continue year after year despite intense control efforts. Nonresidential sites (public and private spaces) infested with Aedes aegypti (L.) were evaluated. In total, 141 nonresidential sites were sampled for the presence of potential and active oviposition sites and adult mosquitoes. Eighty percent of the sites were oviposition sites; Ae. aegypti adults were recovered at 94.7% of nonresidential sites. Most female Ae. aegypti, 21.6 and 10.4, were at schools and recreational sites, respectively. Chi-squared indicated no significant differences in the dengue vector to categories of sample sites (X2 = 17.76, df = 9, P = 0.38). Indoor-use patterns of adult mosquitoes indicated bathrooms and classrooms were preferred resting sites. Reverse transcription polymerase chain reaction (RT-PCR) assay did not identify dengue virus nucleic acids from a group of 221 pools containing 1,521 female Ae. aegypti. Daytime human activities; e.g., school and work, synchronize with the bimodal biting pattern of Ae. aegypti, increasing the chance of transferring dengue virus.

Plant Essential Oils Affect the Toxicities of Carbaryl and Permethrin Against &lt;I&gt;Aedes aegypti&lt;/I&gt; (Diptera: Culicidae)

ABSTRACT Phytochemicals have been considered as alternatives for conventional pesticides because of their low mammalian toxicity and environmental safety. They usually display less potent insecticidal effects than synthetic compounds, but may express as yet unknown modes of action. In the current study, we evaluated 14 plant essential oils for their toxicities and synergistic effects with carbaryl and permethrin against fourth instars of Aedes aegypti (L.) as well as 5-7-d-old adults. Six essential oils showed significant synergistic effects with carbaryl at 10-50 mg/liter, but paradoxically all of them decreased the toxicity of permethrin against Ae. aegypti larvae. None showed toxicity or synergistic effects on Ae. aegypti adults, at doses up to 2,000 ng/ insect. The six essential oils displaying synergistic effects in Ae. aegypti larvae inhibited the in vitro activities of cytochrome P450 monooxygenases and carboxylesterases in the low milligram per liter range. The data indicated that cytochrome P450 monooxygenases and carboxylesterase were probably targets for these natural synergists. Thus, the mechanism of synergism was most likely inhibition of metabolism and not interacting target site effects.

Insecticidal, repellent and fungicidal properties of novel trifluoromethylphenyl amides

Twenty trifluoromethylphenyl amides were synthesized and evaluated as fungicides and as mosquito toxicants and repellents. Against Aedes aegypti larvae, N-(2,6-dichloro-4-(trifluoromethyl)phenyl)-3,5-dinitrobenzamide (1e) was the most toxic compound (24h LC50 1940nM), while against adults N-(2,6-dichloro-4-(trifluoromethyl)phenyl)-2,2,2-trifluoroacetamide (1c) was most active (24h LD50 19.182nM, 0.5μL/insect). However, the 24h LC50 and LD50 values of fipronil against Ae. aegypti larvae and adults were significantly lower: 13.55nM and 0.787×10−4nM, respectively. Compound 1c was also active against Drosophila melanogaster adults with 24h LC50 values of 5.6 and 4.9μg/cm2 for the Oregon-R and 1675 strains, respectively. Fipronil had LC50 values of 0.004 and 0.017μg/cm2 against the two strains of D. melanogaster, respectively. In repellency bioassays against female Ae. aegypti, 2,2,2-trifluoro-N-(2-(trifluoromethyl)phenyl)acetamide (4c) had the highest repellent potency with a minimum effective dosage (MED) of 0.039μmol/cm2 compared to DEET (MED of 0.091μmol/cm2). Compound N-(2-(trifluoromethyl)phenyl)hexanamide (4a) had an MED of 0.091μmol/cm2 which was comparable to DEET. Compound 4c was the most potent fungicide against Phomopsis obscurans. Several trends were discerned between the structural configuration of these molecules and the effect of structural changes on toxicity and repellency. Para- or meta- trifluoromethylphenyl amides with an aromatic ring attached to the carbonyl carbon showed higher toxicity against Ae. aegypti larvae, than ortho- trifluoromethylphenyl amides. Ortho- trifluoromethylphenyl amides with trifluoromethyl or alkyl group attached to the carbonyl carbon produced higher repellent activity against female Ae. aegypti and Anopheles albimanus than meta- or para- trifluoromethylphenyl amides. The presence of 2,6-dichloro- substitution on the phenyl ring of the amide had an influence on larvicidal and repellent activity of para- trifluoromethylphenyl amides.

Effect of Aedes aegypti exposure to spatial repellent chemicals on BG-Sentinel™ trap catches.

BackgroundAn integrated approach to reduce densities of adult Aedes aegypti inside homes is currently being evaluated under experimentally controlled field conditions. The strategy combines a spatial repellent (SR) treatment (applied indoors) with the Biogents Sentinel™ (BGS) mosquito trap positioned in the outdoor environment. In essence, when combined, the goal is to create a push-pull mechanism that will reduce the probability of human-vector contact. The current study measured BGS recapture rates of Ae. aegypti test cohorts that were exposed to either SR or control (chemical-free) treatments within experimental huts. The objective was to define what, if any, negative impact SR may have on BGS trap efficacy (i.e., reduced BGS collection).MethodsAedes aegypti females were exposed to SR compounds within experimental huts in the form of either treated fabric (DDT and transfluthrin) or mosquito coil (metofluthrin). Test cohorts were released within individual screen house cubicles, each containing 4 BGS traps, following SR exposure according to treatment. Two separate test cohorts were evaluated: (i) immediate release (IR) exposed from 06:00–12:00 hours and released at 12:00 hours and (ii) delayed release (DR) exposed from12:00–18:00 hours and released at 05:30 hours the following day. BGS recapture was monitored at 09:30, 13:30 and 15:30 hours and the cumulative recapture by time point quantified.ResultsExposure of Ae. aegypti females to either DDT or metofluthrin did not significantly impact BGS capture as compared to cohorts of non-exposed females. This was true for both IR and DR exposure populations. IR cohorts exposed to transfluthrin resulted in significantly lower BGS recapture compared to matched controls but this effect was primarily due to high mosquito mortality during transfluthrin trials.ConclusionOur data indicate no more than minor and short-lived impacts (i.e., reduced attraction) on BGS trap catches following exposure to the pyrethroid compounds transfluthrin and metofluthrin and no change in recapture densities using DDT as compared to matched controls. These findings suggest a combined SR and BGS approach to vector control could function as a push-pull strategy to reduce Ae. aegypti adults in and around homes.

Lavandula gibsoni and Plectranthus mollis essential oils: chemical analysis and insect control activities against Aedes aegypti, Anopheles sfttephensi and Culex quinquefasciatus

Essential oils and acetone extracts from Lavandula gibsoni and Plectranthus mollis, family Lamiaceae, were investigated for their mosquito larvicidal activity against 4th instar larvae of Aedes aegypti, Anopheles stephensi and Culex quinquefasciatus. LC50 values against these three species were 48.3, 62.8 and 54.7 mg/L for L. gibsoni essential oil and 118.5, 137.2 and 128.1 mg/L, respectively, for its acetone extract, while LC50 values for P. mollis essential oil were 25.4, 33.5 and 29.5 mg/L and 195.0, 213.8 and 209.0 mg/L, respectively, for its acetone extract. Repellence of the essential oils was assessed against A. aegypti adults. L. gibsoni essential oil provided 100 % protection for more than 7 h at a concentration of 2.0 mg/cm2. Under the same conditions, the standard repellent N,N-diethyl-meta-toluamide, at 0.25 mg/cm2, provided 100 % protection for more than 8 h, while P. mollis essential oil was only weakly repellent. The major components from both essential oils were identified based on GC–MS analysis and linear retention indices. Our results demonstrated promising larvicidal activities of both essential oils against these mosquito species. L. gibsoni essential oil also showed promising repellent activity.

First Report on Invasion of Yellow Fever Mosquito, Aedes aegypti, at Narita International Airport, Japan in August 2012

The invasion of the yellow fever mosquito Aedes aegypti at Narita International Airport, Japan was detected for the first time. During the course of routine vector surveillance at Narita International Airport, 27 Ae. aegypti adults emerged from larvae and pupae collected from a single larvitrap placed near No. 88 spot at passenger terminal 2 on August 8, 2012. After the appearance of Ae. aegypti in the larvitrap, we defined a 400-m buffer zone and started an intensive vector survey using an additional 34 larvitraps and 15 CO2 traps. International aircraft and passenger terminal 2 were also inspected, and one Ae. aegypti male was collected from the cargo space of an international aircraft from Darwin via Manila on August 28, 2012. Larvicide treatment with 1.5% fenitrothion was conducted in 64 catch basins and one ditch in the 400-m buffer zone. Twenty-four large water tanks were also treated at least once with 0.5% pyriproxyfen, an insect growth regulator. No Ae. aegypti eggs or adults were found during the 1-month intensive vector survey after finding larvae and pupae in the larvitrap. We concluded that Ae. aegypti had failed to establish a population at Narita International Airport.

Effects of the Botanical Insecticide, Toosendanin, on Blood Digestion and Egg Production by FemaleAedes aegypti(Diptera: Culicidae): Topical Application and Ingestion

Botanical insecticides offer novel chemistries and actions that may provide effective mosquito control. Toosendanin (TSN, 95% purity) is one such insecticide used to control crop pests in China, and in this study, it was evaluated for lethal and sublethal effects on larvae and females of the yellowfever mosquito, Aedes aegypti (L.). TSN was very toxic to first instar larvae after a 24 h exposure (LC50 = 60.8 microg/ml) and to adult females up to 96 h after topical treatment (LD50 = 4.3 microg/female) or ingestion in a sugar bait (LC50 = 1.02 microg/microl). Treatment of first instars for 24 h with a range of sublethal doses (6.3-25 microg/ml) delayed development to pupae by 1 to 2 d. Egg production and larval hatching from eggs were dose dependently reduced (>45%) by TSN doses (1.25-10.0 microg) topically applied to females 24 h before or 1 h after a bloodmeal. Ingestion of TSN (0.031-0.25 microg/microl of sugar bait) by females 24 h before a bloodmeal also greatly reduced egg production and larval hatch; no eggs were oviposited by females ingesting the highest dose. Further studies revealed that topical or ingested TSN dose-dependently disrupted yolk deposition in oocytes, blood ingestion and digestion, and ovary ecdysteroid production in blood-fed females. Overall, our results indicate that TSN is an effective insecticide for Ae. aegypti larvae and adults, because of its overt toxicity at high doses and disruption of development and reproduction at sublethal doses.

Field comparison of thermal and non‐thermal ultra‐low‐volume applications using water and diesel as solvents for managing dengue vector, Aedes aegypti

To compare the effectiveness on Aedes aegypti (Linneo) (Diptera: Culicidae) of a larvicide-adulticide ULV formulation applied by a thermal or a cold fogger using different solvents. We applied, in field conditions, a ULV formulation containing pyriproxyfen and permethrin, using a thermal and a cold fogger and water or diesel as solvent. We determined the effectiveness of these applications on Ae. aegypti adults and larvae by different bioassays and measuring Breteau, house and adult indices. When water was used as solvent, the treatments applied with the cold or the thermal foggers were equally effective on adult mortality (close to 90%) and adult emergence inhibition (% EI) (close to 70%). When the thermal fogger was used with water as solvent, the adult mortality outside the houses (85%) was higher, but not significantly different, than with diesel (65%). The contrary happens inside (22%vs. 58%), while there were no differences in %EI. Adult and larval indices behaved similarly in all areas, with a slight tendency for the treatments applied using water as solvent to be more effective. Water-based formulations are equally or more effective than the one applied with diesel as solvent. The use of water as solvent will not only improve the effectiveness of this formulation but also reduce the environmental impact and costs of spraying compared to the use of diesel.

Impacts ofWolbachiaInfection on Predator Prey Relationships: Evaluating Survival and Horizontal Transfer BetweenwMelPop InfectedAedes aegyptiand Its Predators: Table 1.

The wMelPop strain of Wolbachia is currently being investigated for its potential use as a biological control agent to reduce the ability of Aedes aegypti (L.) mosquitoes to transmit dengue viruses. The survival of a potential wMelPop infected Ae. aegypti strain for field release is important as a higher susceptibility to predation in the wMelPop strain could result in difficulties in achieving fixation. We investigated immature and adult survival as a function of susceptibility to predation by six naturally occurring predator species; cyclopoid copepods, fish, predatory Toxorhynchites mosquito larvae and a salticid jumping spider. The trials indicated that wMelPop infected and uninfected Ae. aegypti larvae and adults were equally susceptible to predation to all six tested predators. In addition to evaluating any potential fitness costs to the infected host, we were unable to demonstrate horizontal transfer of wMelPop via consumption of infected Ae. aegypti larvae to the above predators. That susceptibility to predation was consistent across mosquito life stage, predator species and experimental venue is strong evidence that despite the neurotrophic and extensive nature of wMelPop infection, behavioral changes are not occurring, or at least not a determining factor in survival when exposed to a predator. Based on our results and the ecology of Wolbachia and mosquito predators, horizontal transfer of wMelPop from Ae. aegypti into naturally occurring predators is not cause for concern.

Essential oils of Cupressus funebris, Juniperus communis, and J. chinensis (Cupressaceae) as repellents against ticks (Acari: Ixodidae) and mosquitoes (Diptera: Culicidae) and as toxicants against mosquitoes

Juniperus communis leaf oil, J. chinensis wood oil, and Cupressus funebris wood oil (Cupressaceae) from China were analyzed by gas chromatography and gas chromatography-mass spectrometry. We identified 104 compounds, representing 66.8-95.5% of the oils. The major components were: α-pinene (27.0%), α-terpinene (14.0%), and linalool (10.9%) for J. communis; cuparene (11.3%) and δ-cadinene (7.8%) for J. chinensis; and α-cedrene (16.9%), cedrol (7.6%), and β-cedrene (5.7%) for C. funebris. The essential oils of C. funebris, J. chinensis, and J. communis were evaluated for repellency against adult yellow fever mosquitoes, Aedes aegypti (L.), host-seeking nymphs of the lone star tick, Amblyomma americanum (L.), and the blacklegged tick, Ixodes scapularis Say, and for toxicity against Ae. aegypti larvae and adults, all in laboratory bioassays. All the oils were repellent to both species of ticks. The EC(95) values of C. funebris, J. communis, and J. chinensis against A. americanum were 0.426, 0.508, and 0.917 mg oil/cm(2) filter paper, respectively, compared to 0.683 mg deet/cm(2) filter paper. All I. scapularis nymphs were repelled by 0.103 mg oil/cm(2) filter paper of C. funebris oil. At 4 h after application, 0.827 mg oil/cm(2) filter paper, C. funebris and J. chinensis oils repelled ≥80% of A. americanum nymphs. The oils of C. funebris and J. chinensis did not prevent female Ae. aegypti from biting at the highest dosage tested (1.500 mg/cm(2) ). However, the oil of J. communis had a Minimum Effective Dosage (estimate of ED(99) ) for repellency of 0.029 ± 0.018 mg/cm(2) ; this oil was nearly as potent as deet. The oil of J. chinensis showed a mild ability to kill Ae. aegypti larvae, at 80 and 100% at 125 and 250 ppm, respectively.

Aedes aegypti Susceptibility to Insecticide from Abidjan City, Cote D'ivoire

The susceptibility of Aedes aegypti adults of three places in Abidjan city selected for an entomological surveillance of potential arbovirus vectors to permethrin, deltamethrin, lambdacyhalothrin, and propoxur was determined using WHO standard procedures. The wild populations of A. aegypti were susceptible to permethrin, deltamethirn, and lambdacyhalothin. Resistance to propoxur was detected in strains collected at the Autonomous Port of Abidjan and at Koumassi (mortality rate: 77%) but possibly resistance to this insecticide at the national zoological park (mortality rate: 90.8%). Populations of the national zoological park were possibly resistant to propoxur whereas those of the Autonomous port of Abidjan and of Koumassi were resistant.