Area-wide management of Aedes albopictus: choice of study sites based on geospatial characteristics, socioeconomic factors and mosquito populations

BACKGROUND: Aedes (Stegomyia) albopictus (Skuse), the Asian tiger mosquito, is an introduced invasive species in the United States that is responsible for a significant proportion of service requests to local mosquito control programs. This container‐utilizing mosquito is refractory to standard mosquito abatement measures in the United States. This study is part of a USDA‐ARS project to develop an area‐wide management strategy for Ae. albopictus. The goal was to identify three study sites, similar in socioeconomic parameters, geography and Ae. albopictus abundance, in urban and suburban areas in Mercer and Monmouth counties in New Jersey. Prior service requests and light trap counts and also detailed county maps were used to chose nine preliminary sites (four in Mercer and five in Monmouth) where weekly surveillance for Ae. albopictus was performed throughout the 2008 active season. RESULTS: Although outliers were detected, socioeconomic variables in the study sites within each county were fairly consistent. Ae. albopictus abundance was associated with poverty levels and had the highest maxima in Mercer, although average mosquito abundance was similar in urban Mercer and suburban Monmouth. CONCLUSION: Three study sites in each county were identified for future studies. The summer‐long surveillance also revealed socioeconomic variables critical for the development of integrated mosquito management. Copyright © 2011 Society of Chemical Industry     

Insecticidal activities of leaf and twig essential oils from Clausena excavata against Aedes aegypti and Aedes albopictus larvae

BACKGROUND: The current study investigates, for the first time, the mosquito larvicidal activities of leaf and twig essential oils from Clausena excavata Burm. f. and their individual constituents against Aedes aegypti L. and Aedes albopictus Skuse larvae. The yields of essential oils obtained from hydrodistillation were compared, and their constituents were determined by GC‐MS analyses. RESULTS: The LC₅₀ values of leaf and twig essential oils against fourth‐instar larvae of Ae. aegypti and Ae. albopictus were 37.1–40.1 µg mL^?1 and 41.1–41.2 µg mL^?1 respectively. This study demonstrated that C. excavata leaf and twig essential oils possess mosquito larvicidal activity, inhibiting the growth of mosquito larvae for both species at a low concentration. In addition, results of larvicidal assays showed that the effective constituents in leaf and twig essential oils were limonene, γ‐terpinene, terpinolene, β‐myrcene, 3‐carene and p‐cymene. The LC₅₀ values of these constituents against both mosquito larvae were below 50 µg mL^?1. Among these effective constituents, limonene had the best mosquito larvicidal activity, with LC₅₀ of 19.4 µg mL^?1 and 15.0 µg mL^?1 against Ae. aegypti and Ae. albopictus larvae respectively. CONCLUSION: The findings suggested that the essential oils from Clausena excavata leaf and twig and their effective constituents may be explored as a potential natural larvicide. Copyright © 2008 Society of Chemical Industry     

Larvicidal and oviposition‐altering activity of monoterpenoids,trans‐anithole and rosemary oil to the yellow fever mosquito Aedes aegypti (Diptera: Culicidae)

BACKGROUND: Aedes aegypti L. is the major vector of dengue fever and dengue hemorrhagic fever. In an effort to find effective tools for control programs to reduce mosquito populations, the authors assessed the acute toxicities of 14 monoterpenoids, trans‐anithole and the essential oil of rosemary against different larval stages of Ae. aegypti. The potential for piperonyl butoxide (PBO) to act as a synergist for these compounds to increase larvicidal activity was also examined, and the oviposition response of gravid Ae. aegypti females to substrates containing these compounds was evaluated in behavioral bioassays. RESULTS: Pulegone, thymol, eugenol, trans‐anithole, rosemary oil and citronellal showed high larvicidal activity against all larval stages of Ae. aegypti (LC₅₀ values 10.3–40.8 mg L^?1). The addition of PBO significantly increased the larvicidal activity of all test compounds (3–250‐fold). Eugenol, citronellal, thymol, pulegone, rosemary oil and cymene showed oviposition deterrent and/or repellent activities, while the presence of borneol, camphor and β‐pinene increased the number of eggs laid in test containers. CONCLUSIONS: This study quantified the lethal and sublethal effects of several phytochemical compounds against all larval stages of Aedes aegypti, providing information that ultimately may have potential in mosquito control programs through acute toxicity and/or the ability to alter reproductive behaviors. Copyright © 2008 Society of Chemical Industry     

Effects of radiation on the fitness,sterility and arbovirus susceptibility of a Wolbachia-free Aedes albopictus strain for use in the sterile insect technique

BACKGROUND

The sterile insect technique (SIT) is a green and species-specific insect pest control technique that suppresses target populations by releasing factory-reared, radiosterilized males into the wild. Once released, it is important to be able to distinguish the released males from the wild males for monitoring purposes. Several methods to mark the sterile males exist. However, most have limitations due to monetary, process efficiency, or insect quality. Aedes albopictus is naturally infected with Wolbachia at a high prevalence, therefore the elimination of Wolbachia can serve as a biomarker to distinguish factory-reared male mosquitoes from wild conspecifics.

RESULTS

In this study, a Wolbachia-free Ae. albopictus GT strain was developed and its fitness evaluated, which was found to be comparable to the wild GUA strain. In addition, GT male mosquitoes were irradiated at the adult stage and a dose of 20 Gy or more induced over 99% sterility. Moreover, a dose of 30 Gy (almost completely sterilizing male and female mosquitoes) had limited effects on the mating competitiveness of GT males and the vector competence of GT females, respectively. However, radiation reduced mosquito longevity, regardless of sex.

CONCLUSION

Our results indicate that the Ae. albopictus GT strain can be distinguished from wild mosquitoes based on Wolbachia status and shows similar fitness, radio-sensitivity and arbovirus susceptibility to the GUA strain, indicating that it is feasible to use the GT strain to suppress Ae. albopictus populations for SIT programmes. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.     

Evaluation of semiochemical toxicity to Aedes aegypti,Ae. albopictus and Anopheles quadrimaculatus (Diptera: Culicidae)

BACKGROUND: Mosquitoes are the most important vectors of human pathogens. Wide‐scale use of pesticides has led to the development of resistance to most common insecticide groups. The need to develop novel products that have a low impact on human health and the environment is well established. The toxicity of selected semiochemicals with molecular structures indicative of insecticidal activity was determined against adult Aedes aegypti (L.) and Anopheles quadrimaculatus (Say). The two most active insecticides against Ae. aegypti were also evaluated against Ae. albopictus (Skuse). RESULTS: Fifteen semiochemicals classified as terpenoid alcohols, ketones or carboxylic esters showed toxicity to both mosquito species. Geranyl acetone (LC₅₀ = 38.51 µg cm^?2) followed by citronellol (LC₅₀ = 48.55 µg cm^?2) were the most toxic compounds to Ae. aegypti, while geraniol and lavonax, with LC₅₀ values of 31.88 and 43.40 µg cm^?2, showed the highest toxicity to An. quadrimaculatus. Both geranyl acetone and citronellol were highly toxic to Ae. albopioctus. No semiochemical showed fumigation activity against either species. All semiochemicals persisted for less than 24 h when tested on filter paper. CONCLUSION: Quantification of LC₅₀ values of several semiochemicals against Ae. Aegypti, An. quadrimaculatus and Ae. albopioctus showed that semiochemicals not only modify insect behaviors but also hold potential as potent insecticides for mosquito control programs. Copyright © 2010 Society of Chemical Industry     

Spinosad as an effective larvicide for control of Aedes albopictus and Aedes aegypti, vectors of dengue in southern Mexico

BACKGROUND: Field trials were conducted during the wet and dry seasons in periurban and semi‐rural cemeteries in southern Mexico to determine the efficacy of a suspension concentrate formulation of spinosad (Tracer 480SC) on the inhibition of development of Aedes albopictus L. and Ae. aegypti Skuse. For this, oviposition traps were treated with spinosad (1 or 5 mg L^?1), Bacillus thuringiensis israelensis (Bti, VectoBac 12AS), a sustained release formulation of temephos and a water control. RESULTS: Ae. albopictus was subordinate to Ae. aegypti during the dry season, but became dominant or codominant during the wet season at both sites. The two species could not be differentiated in field counts on oviposition traps. Mean numbers of larvae + pupae of Aedes spp. in Bti‐treated containers were similar to the control at both sites during both seasons. The duration of complete absence of aquatic stages varied from 5 to 13 weeks for the spinosad treatments and from 6 to 9 weeks for the temephos treatment, depending on site, season and product concentration. Predatory Toxorhynchites theobaldi Dyar and Knab suffered low mortality in control and Bti treatments, but high mortality in spinosad and temephos treatments. Egg counts and percentage of egg hatch of Aedes spp. increased significantly between the dry and wet seasons, but significant treatment differences were not detected. CONCLUSION: Temephos granules and a suspension concentrate formulation of spinosad were both highly effective larvicides against Ae. aegypti and Ae. albopictus. These compounds merit detailed evaluation for inclusion in integrated control programs targeted at Ae. aegypti and Ae. albopictus in regions where they represent important vectors of human diseases. Copyright © 2010 Society of Chemical Industry     

A bacterium against the tiger: further evidence of the potential of noninundative releases of males with manipulated Wolbachia infection in reducing fertility of Aedes albopictus field populations in Italy

BACKGROUND

Incompatible insect technique (IIT) is a population suppression approach based on the release of males with manipulated Wolbachia infection inducing egg inviability in wild females. We here present results of multiple field releases of incompatible ARwP males carried out in 2019 in a 2.7-ha green area within urban Rome (Italy) to assess the effect on Aedes albopictus egg viability. Data are compared with results obtained in 2018, when the approach was tested for the first time in Europe.

RESULTS

An average of 4674 ARwP males were released weekly for 7 weeks, resulting in a mean ARwP:wild male ratio of 1.1:1 (versus 0.7:1 in 2018). Egg-viability dynamics in ovitraps significantly varied between treated and control sites, with an estimated overall reduction of 35% (versus 15% in 2018). The estimated proportion of females classified as mated with ARwP males was 41.8% and the viability rate of eggs laid by these females (9.5%) was on average significantly lower than that of females only mated with wild males (87.8%); however, high variability in fertility was observed. Values of ARwP male competitiveness were 0.36 and 0.73 based on the overall viability rate of eggs in ovitraps and on female fertility, respectively; thus, well above the conventional 0.2 threshold for an effective suppressive impact in the field.

CONCLUSIONS

Results further support the potential of IIT as a tool to contribute to Ae. albopictus control in the urban context, stressing the need for larger field trials to evaluate the cost-efficacy of the approach in temperate regions. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.     

Insecticide resistance and,efficacy of space spraying and larviciding in the control of dengue vectors Aedes aegypti and Aedes albopictus in Sri Lanka

Unprecedented incidence of dengue has been recorded in Sri Lanka in recent times. Source reduction and use of insecticides in space spraying/fogging and larviciding, are the primary means of controlling the vector mosquitoes Aedes aegypti and Ae. albopictus in the island nation. A study was carried out to understand insecticide cross-resistance spectra and mechanisms of insecticide resistance of both these vectors from six administrative districts, i.e. Kandy, Kurunegala, Puttalam, Gampaha, Ratnapura and Jaffna, of Sri Lanka. Efficacy of the recommended dosages of frequently used insecticides in space spraying and larviciding in dengue vector control programmes was also tested.     

Experimental comparison of aerial larvicides and habitat modification for controlling disease-carrying Aedes vigilax mosquitoes

BACKGROUND: Microbial and insect‐growth‐regulator larvicides dominate current vector control programmes because they reduce larval abundance and are relatively environmentally benign. However, their short persistence makes them expensive, and environmental manipulation of larval habitat might be an alternative control measure. Aedes vigilax is a major vector species in northern Australia. A field experiment was implemented in Darwin, Australia, to test the hypotheses that (1) aerial microbial larvicide application effectively decreases Ae. vigilax larval presence, and therefore adult emergence, and (2) environmental manipulation is an effective alternative control measure. Generalised linear and mixed‐effects modelling and information‐theoretic comparisons were used to test these hypotheses. RESULTS: It is shown that the current aerial larvicide application campaign is effective at suppressing the emergence of Ae. vigilax, whereas vegetation removal is not as effective in this context. In addition, the results indicate that current larval sampling procedures are inadequate for quantifying larval abundance or adult emergence. CONCLUSIONS: This field‐based comparison has shown that the existing larviciding campaign is more effective than a simple environmental management strategy for mosquito control. It has also identified an important knowledge gap in the use of larval sampling to evaluate the effectiveness of vector control strategies. Copyright © 2011 Society of Chemical Industry     

Paradoxical effects of sublethal exposure to the naturally derived insecticide spinosad in the dengue vector mosquito,Aedes aegypti

BACKGROUND: Recent studies have indicated that spinosad, a mixture of two tetracyclic macrolide compounds produced during the fermentation of a soil actinomycete, may be suitable for controlling a number of medically important mosquito species, including the dengue vector, Aedes aegypti L. The authors determined the effects of a 1 h exposure to a 50% lethal concentration (LC₅₀) of spinosad in the larval stage on the wing length, longevity and reproductive capacity of the adult survivors. RESULTS: The LC₅₀ of spinosad for a wild‐caught population of Ae. aegypti from Chiapas, southern Mexico, was estimated to be 0.06 mg AI L^?1 in late third instars. Paradoxically, the female survivors of exposure to this concentration were significantly larger (as determined by wing length) laid more eggs, but were slightly less fertile than control females. This was probably due to elimination of the smaller and more susceptible fraction of mosquito larvae from the experimental population following spinosad treatment. Male survivors, in contrast, were significantly smaller than controls. No significant differences were detected in the adult longevity of treated and control insects of either sex. CONCLUSIONS: The increase in reproductive capacity of spinosad‐treated females did not compensate for mortality in the larval stage and would be unlikely to result in population increase in this mosquito under the conditions that were employed. Sustained‐release formulations would likely assist in minimizing the occurrence of sublethal concentrations of this naturally derived product in mosquito breeding sites. Copyright © 2008 Society of Chemical Industry     

Control methods against invasive Aedes mosquitoes in Europe: a review

Five species of invasive Aedes mosquitoes have recently become established in Europe: Ae. albopictus, Ae. aegypti, Ae. japonicus japonicus, Ae. koreicus and Ae. atropalpus. These mosquitoes are a serious nuisance for people and are also competent vectors for several exotic pathogens such as dengue and chikungunya viruses. As they are a growing public health concern, methods to control these mosquitoes need to be implemented to reduce their biting and their potential for disease transmission. There is a crucial need to evaluate methods as part of an integrated invasive mosquito species control strategy in different European countries, taking into account local Aedes infestations and European regulations. This review presents the control methods available or in development against invasive Aedes mosquitoes, with a particular focus on those that can be implemented in Europe. These control methods are divided into five categories: environmental (source reduction), mechanical (trapping), biological (e.g. copepods, Bacillus thuringiensis var. israelensis, Wolbachia), chemical (insect growth regulators, pyrethroids) and genetic (sterile insect technique and genetically modified mosquitoes). We discuss the effectiveness, ecological impact, sustainability and stage of development of each control method. © 2015 Society of Chemical Industry     

Insecticide resistance compromises the control of Aedes aegypti in Bangladesh

BACKGROUND

With no effective drugs or widely available vaccines, dengue control in Bangladesh is dependent on targeting the primary vector Aedes aegypti with insecticides and larval source management. Despite these interventions, the dengue burden is increasing in Bangladesh, and the country experienced its worst outbreak in 2019 with 101 354 hospitalized cases. This may be partially facilitated by the presence of intense insecticide resistance in vector populations. Here, we describe the intensity and mechanisms of resistance to insecticides commonly deployed against Ae. aegypti in Dhaka, Bangladesh.

RESULTS

Dhaka Ae. aegypti colonies exhibited high-intensity resistance to pyrethroids. Using CDC bottle assays, we recorded 2–24% mortality (recorded at 24 h) to permethrin and 48–94% mortality to deltamethrin, at 10× the diagnostic dose. Bioassays conducted using insecticide–synergist combinations suggested that metabolic mechanisms were contributing to pyrethroid resistance, specifically multi-function oxidases, esterases, and glutathione S-transferases. In addition, kdr alleles were detected, with a high frequency (78–98%) of homozygotes for the V1016G mutation. A large proportion (≤ 74%) of free-flying and resting mosquitoes from Dhaka colonies survived exposure to standard applications of pyrethroid aerosols in an experimental free-flight room. Although that exposure affected the immediate host-seeking behavior of Ae. aegypti, the effect was transient in surviving mosquitoes.

CONCLUSION

The intense resistance characterized in this study is likely compromising the operational effectiveness of pyrethroids against Ae. aegypti in Dhaka. Switching to alternative chemical classes may offer a medium-term solution, but ultimately a more sustainable and effective approach to controlling dengue vectors is required. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.     

Enhanced activity of an insecticidal protein, trypsin modulating oostatic factor (TMOF), through conjugation with aliphatic polyethylene glycol

BACKGROUND: Trypsin modulating oostatic factor (TMOF), a decapeptide (Tyr-Asp-Pro-Ala-Pro₆) isolated from the ovaries of the adult yellow fever mosquito, Aedes aegypti, regulates trypsin biosynthesis. TMOF per os is insecticidal to larval mosquitoes and a good model for the development of technologies to enhance protein insecticide activity by reduced catabolism and/or enhanced delivery to the target. RESULTS: TFA-TMOF-K (TFA = trifluoro acetyl) allowed the specific conjugation of monodispersed, aliphatic polyethylene glycol (PEG) to the amino group of lysine-producing TMOF-K-methyl(ethyleneglycol)₇-O-propionyl (TMOF-K-PEG₇P). The addition of lysine to TMOF reduced its per os larval mosquitocidal activity relative to the parent TMOF, but conjugation of TMOF-K with methyl(ethyleneglycol)₇-O-propionyl increased its toxicity 5.8- and 10.1-fold above that of TMOF and TMOF-K for Ae. aegypti. Enhanced insecticidal activity was also found for larval Ae. albopictus and for neonates of Heliothis virescens and Heliocoverpa zea. Only TMOF-K was found by MS/MS in the hemolymph for H. virescens fed on TMOF-K-PEG₇P. No TMOF, TMOF-K or PEGylated TMOF-K was detected in the hemolymph after topical applications. CONCLUSIONS: This research suggests that aliphatic PEG polymers can be used as a new method for increasing the activity of insecticidal proteins. Copyright © 2011 Society of Chemical Industry     

毒死蜱微球和乳油在水中的消解动态及其对白纹伊蚊幼虫的毒力

室内条件下,研究了不同浓度毒死蜱微球和毒死蜱乳油在水中的消解动态及其对白纹伊蚊Aedes albopictus 3龄幼虫的持续毒杀作用。结果表明:毒死蜱微球在水中的消解速率比乳油慢,半 衰期比乳油的长,高浓度微球和乳油的消解半衰期均长于低浓度下的消解半衰期。有效成分为1.2、 12和24 mg/L的毒死蜱微球和毒死蜱乳油在水中的消解半衰期分别为(19.4±2.1) d、(27.8±1.6) d、(31.0±1.7) d和(12.8±1.0) d、(16.1±0.9) d、(19.7±1.1) d;毒死蜱微球对白纹伊蚊3龄幼虫的毒杀作用强于乳油且持效期长,1.2 mg/L的毒死蜱微球水解85 d后处理白纹伊蚊3龄幼虫的死亡率高达76.6%,高于相同浓度、相同条件乳油的处理(53.3%),具有良好的持效性。     

Thermal behaviour and biological activity against Aedes aegypti (Diptera: Culicidae) of permethrin and pyriproxyfen in a smoke‐generating formulation

BACKGROUND: The most common ways to control dengue vector Aedes aegypti (L.) are larval source reduction in domestic habitats and ground application of small quantities of aerosol insecticide (ultralow volume). Nevertheless, these actions have been shown repeatedly to be ineffective in controlling Ae. aegypti populations. RESULTS: The efficacy of a new smoke‐generating formulation containing pyriproxyfen and permethrin was evaluated in the laboratory. Smoke‐generating tablets containing each insecticide individually or combined were prepared, and the recovery of the insecticides from the smoke was determined. Recovery values of over 90% were obtained for pyriproxyfen, and around 50% for permethrin. The biological efficacy of pyriproxyfen released in the smoke was evaluated in the laboratory, on late third‐instar or early fourth‐instar Ae. aegypti larvae, using different concentrations of pyriproxyfen and exposure times. Adult emergence inhibition (EI) values of 100% were obtained at 30 min, and a dose‐dependent effect was observed at 5 min. The effect of pyriproxyfen released in the smoke was due to direct contact with the larvicide in the water rather than by inhalation of the fumes. The efficacy of permethrin released in the fumes was also evaluated as knockdown effect (KT₅₀) on adults for a tablet containing permethrin alone or permethrin plus pyriproxyfen. There was no significant difference in KT₅₀ values obtained for permethrin (KT₅₀ = 19.9 min) and permethrin plus pyriproxyfen (KT₅₀ = 19.4 min). CONCLUSION: The excellent laboratory performance of this new formulation on immature stages and adults indicates that a smoke‐generating tablet containing pyriproxyfen and permethrin could be a new tool for controlling mosquitoes. Copyright © 2009 Society of Chemical Industry     

Receptor-binding affinity and larvicidal activity of tetrahydroquinoline-type ecdysone agonists against Aedes albopictus

Tetrahydroquinolines (THQs), a class of nonsteroidal ecdysone agonists, are good candidates for novel mosquito control agents because they specifically bind to mosquito ecdysone receptors (EcRs). We have recently performed quantitative structure–activity relationship (QSAR) analyses of THQs to elucidate the physicochemical properties important for the ligand–receptor interaction. Based on previous QSAR results, here, we newly synthesized 15 THQ analogs with a heteroaryl group at the acyl moiety and evaluated their binding affinity against Aedes albopictus EcRs. We also measured the larvicidal activity of the combined set of previously and newly synthesized compounds against A. albopictus to examine the contribution of receptor-binding to larvicidal activity. Multiple regression analyses showed that the binding affinity and the molecular hydrophobicity of THQs are the key determinants of their larvicidal activity.     

Mosquito adulticidal activity of a biosurfactant produced by Bacillus subtilis subsp. subtilis

BACKGROUND: A biosurfactant, surfactin, produced by a strain of Bacillus subtilis subsp. subtilis (VCRC B471), was effective in killing mosquito larval and pupal stages. As it was lethal to the non‐feeding pupal stage, it was presumed that it could kill the adult mosquitoes also. In this study, the adulticidal effect of the biosurfactant was assessed in the laboratory against a malaria vector, Anopheles stephensi. RESULTS: The biosurfactant surfactin, separated from the culture supernatant of the production strain, showed mosquito adulticidal activity when tested as ultralow‐volume (ULV) spray in a Peet‐Grady chamber. Knockdown activity and mortality were found to increase with increasing surfactin dosage. Knockdown dosage (KD) and lethal dosage (LD) were calculated by statistical analysis. The KD₅₀ and KD₉₀ dosages were 10.73 and 26.39 mg m^?3 respectively. The LD₅₀ and LD₉₀ dosages were 16.13 and 39.21 mg m^?3. The average droplet size of B. subtilis surfactin was 17.5 ± 1.07 µm. CONCLUSION: The present study indicates that the biosurfactant surfactin, produced by B. subtilis subsp. subtilis (VCRC B471), is a potential bioadulticide for ULV spray against malaria‐transmitting Anopheles stephensi mosquitoes. This is the first report of a mosquito adulticide from a microbial source. Copyright © 2012 Society of Chemical Industry     

Insecticide resistance in vector mosquitoes in China

Because of their special behaviour, physiology and close relationship with humans, mosquitoes act as one of the most important vectors of human diseases, such as filariasis, Japanese encephalitis, dengue and malaria. The major vector mosquitoes are members of the Culex, Aedes and Anopheles genera. Insecticides play important roles in agricultural production and public health, especially in a country with a huge human population, like China. Large quantities of four classes of insecticides, organochlorines, organophosphates, carbamates and pyrethroids, are applied annually to fields or indoors in China, directly or indirectly bringing heavy selection pressure on vector populations. The seven major species of vector mosquito in China are the Culex pipiens L. complex, C. tritaeniorhynchus Giles, Anopheles sinensis Wied., A. minimus Theobald, A. anthropophagus Xu & Feng, Aedes albopictus (Skuse) and Ae. aegypti L., and all have evolved resistance to all the above types of insecticide except the carbamates. The degree of resistance varies among mosquito species, insecticide classes and regions. This review summarizes the resistance status of these important vector mosquitoes, according to data reported since the 1990s, in order to improve resistance management and epidemic disease control, and to communicate this information from China to the wider community.     

First insights into insecticidal activity against Aedes aegypti and partial biochemical characterization of a novel low molecular mass chymotrypsin‐trypsin inhibitor purified from Lonchocarpus sericeus seeds

BACKGROUND

Arboviroses such as dengue, Zika and chikungunya represent a serious public health issue as a consequence of the absence of approved vaccines or specific antiviral drugs against the arboviruses that cause them. One way to prevent these diseases is by combating the vector mosquito, Aedes aegypti (Diptera), which has serine proteases in the midgut. Protease inhibitors are molecules that can block enzyme activity, impairing digestion and nutrition, which can lead to death. Thus, we purified and characterized a novel chymotrypsin‐trypsin inhibitor (LsCTI) from Lonchocarpus sericeus seeds and investigated its effect upon Ae. aegypti egg hatching, larval development and digestive proteases.

RESULTS

LsCTI showed a single protein band in sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS‐PAGE), and the molecular mass determined by matrix‐assisted laser desorption ionization time‐of‐flight mass spectrometry (MALDI‐TOF‐MS) was 8870.45 Da. Kinetics analyses revealed a noncompetitive type of inhibition and low inhibition constant (K_i) for chymotrypsin (8.24 x 10^‐8 m ). The thermal resistance was remarkable, even at 100 °C for 180 min. The inhibitor concentration required for 50‐percent enzyme inhibition (IC₅₀) of LsCTI was 4.7 x 10^‐7 m for Ae. aegypti midgut larval enzymes. LsCTI did not affect egg hatchability at 0.3 mg mL^‐1, but caused a high larval mortality rate (77%) and delayed development (37%).

CONCLUSIONS

LsCTI is a novel protease inhibitor with remarkable biochemical characteristics and is a potential tool to control Ae. aegypti development. © 2017 Society of Chemical Industry