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Excito-repellent activity of β-caryophyllene oxide against Aedes aegypti and Anopheles minimus

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... This compound is a common sesquiterpene present in many well-known aromatic repellent plants, such as cloves, basil, cinnamon, and citrus 14 . A more recent study showed that BCO is an e cient mosquito repellent 15 and other studies have shown that vetiver oil exhibits irritant and repellent activities against mosquitoes 16 . ...
... Plant-based candidates, VO and BCO, were initially selected based on our previous studies 15,16,20,21 . A more recent study reported that β-caryophyllene oxide at 1% showed spatial repellency against Ae. ...
... An. dirus (32.73%), and An. minimus (92.2%) 15 . On the other hand, essential oil from vetiver oil at 2.5-5% elicited great repellency responses in Ae. albopictus (63.7%) and An. ...
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Mosquito repellents play a major role in reducing the risk of mosquito borne diseases by preventing mosquito bites. The present study evaluated the mosquito-repellent activity of β-caryophyllene oxide 1% (BCO), vetiver oil 2.5% (VO) and their binary mixtures [BCO+VO (1:1), BCO+VO (2:1), BCO+VO (1:2)] against four laboratory-colonized mosquito species: Aedes aegypti (L.), Aedes albopictus (Skuse), Anopheles minimus (Theobald), and Culex quinquefasciatus Say using an excito-repellency assay system. In general, the compound mixtures produced a much stronger response by the mosquitoes than single compounds, regardless of the test conditions and species. The greatest synergetic effect was achieved for the combination of BCO+VO (1:2) in both the contact and non-contact trials with An. minimus (74.07–78.18%) and Cx. quinquefasciatus (55.36–83.64%). Knockdown responses to the binary mixture of BCO+VO were observed for Ae. albopictus, An. minimus and Cx. quinquefasciatus, in the range 18.18–33.33%. The synergistic repellent activity of BCO and VO used in the study may support increased opportunities to develop safer alternatives to synthetic repellents for personal protection against mosquitoes.
... EβCs are probably being expressed in Vitex species; EβC was identified as the main product and α -humulene as the secondary product or in lower concentrations. On the other hand, there are no reports in the literature of specific shyntases for caryophyllene oxide; however, there is a consensus that it is formed by oxidation of EβC [108][109][110]. ...
... Caryophyllene oxide showed toxicity against the aphid Metopolophium dirhodum (Hemiptera: Aphididae), and in mixtures with citral and EβC, it was also effective against the aphid Myzus persicae [108,179]. This compound also showed excellent repellent properties against A. aegypti and Anopheles minimus mosquitoes, with better performance than the commercial repellent N,N-diethyl-meta-toluamide (DEET) [109]. Furthermore, it is one of the main constituents of the oil of Artabotrys hexapetalus Bhandari, which was shown to have strong repellent activity against females of Anopheles gambiae, a species of malaria vector in Africa [180]. ...
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Sesquiterpenes (SS) are secondary metabolites formed by the bonding of 3 isoprene (C5) units. They play an important role in the defense and signaling of plants to adapt to the environment , face stress, and communicate with the outside world, and their evolutionary history is closely related to their physiological functions. This review considers their presence and extensively summarizes the 156 sesquiterpenes identified in Vitex taxa, emphasizing those with higher concentrations and frequency among species and correlating with the insecticidal activities and defensive responses reported in the literature. In addition, we classify the SS based on their chemical structures and addresses cyclization in biosynthetic origin. Most relevant sesquiterpenes of the Vitex genus are derived from the germacredienyl cation mainly via bicyclogermacrene and ger-macrene C, giving rise to aromadrendanes, a skeleton with the highest number of representative compounds in this genus, and 6,9-guaiadiene, respectively, indicating the production of 1.10-cyclizing sesquiterpene synthases. These enzymes can play an important role in the chemo-systematics of the genus from their corresponding routes and cyclizations, constituting a new approach to chemotaxonomy. In conclusion, this review is a compilation of detailed information on the profile of sesquiterpene in the Vitex genus and, thus, points to new unexplored horizons for future research.
... Sulcatone has been reported to be potent against Drosophila melanogaster and Toxorhynchites amboinensis [57]. This inference is in consonance with the studies of Angraeni et al. [58] and Nararak et al. [59,60]. Most insect repellents, including DEET, have a species-specific method of action that is sometimes unknown. ...
... Sulcatone has been reported to be potent against Drosophila melanogaster and Toxorhynchites amboinensis [57]. This inference is in consonance with the studies of Angraeni et al. [58] and Nararak et al. [59,60]. ...
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Background: Essential oil from Vitex negundo is known to have repellent and insecticidal properties toward the Anopheles gambiae and this is linked to its monoterpene and sesquiterpene content. In this work, an effort is made to delineate the constitution of V. negundo essential oil (VNEO) and their interaction with odorant-binding proteins (OBPs) of A. gambiae and hence access its repellent efficiency as cost-effective and safer malaria vector control alternatives. (2) Methods: Anopheles species authentication was performed by genomic DNA analysis and was subjected to behavioral analysis. GC-MS profiling was used to identify individual components of VNEO. Anopheles OBPs were obtained from the RCSB protein data bank and used for docking studies. Determination of ligand efficiency metrics and QSAR studies were performed using Hyper Chem Professional 8.0.3, and molecular dynamics simulations were performed using the Desmond module. (3) Results: GCMS analysis of VNEO showed 28 compounds (monoterpenes, 80.16%; sesquiterpenes, 7.63%; and unknown constituents, 10.88%). The ligand efficiency metrics of all four ligands against the OBP 7 were within acceptable ranges. β-selinene (−12.2 kcal/mol), β-caryophellene (−9.5 kcal/mol), sulcatone (−10.9 kcal/mol), and α-ylangene (−9.3 kcal/mol) showed the strongest binding affinities for the target proteins. The most stable hydrophobic interactions were observed between β-selinene (Phe111 and Phe120), Sulcatone (Phe54 and Phe120), and α-ylangene (Phe111), while only sulcatone (Tyr49) presented H-bond interactions in the simulated environment. (4) Conclusions: Sulcatone and β-caryophyllene presented the best log p values, 6.45 and 5.20, respectively. These lead phytocompounds can be used in their purest as repellent supplement or as a natural anti-mosquito agent in product formulations.
... At present, the development of natural product-based repellents with more effective and long-lasting protection is under study. Many active ingredients have been studied, most of them being essential oils [131][132][133][134]. Studies have shown that 2 plant-based compounds such as β-caryophyllene oxide [135] and vetiver oil [136] have great potentials as natural insect repellents against A. minimus, A. dirus, A. albopictus, and A. aegypti. These plant-based repellents were shown to be environmentally friendly and safe for public use [135,137]. ...
... Many active ingredients have been studied, most of them being essential oils [131][132][133][134]. Studies have shown that 2 plant-based compounds such as β-caryophyllene oxide [135] and vetiver oil [136] have great potentials as natural insect repellents against A. minimus, A. dirus, A. albopictus, and A. aegypti. These plant-based repellents were shown to be environmentally friendly and safe for public use [135,137]. ...
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Residual malaria transmission is the actual maintained inoculation of Plasmodium, in spite of a well-designed and implemented vector control programs, and is of great concern for malaria elimination. Residual malaria transmission occurs under several possible circumstances, among which the presence of exophilic vector species, such as Anopheles dirus, or indoor- and outdoor-biting vectors, such as Anopheles nili, or specific behavior, such as feeding on humans indoors, then resting or leaving the house the same night (such as Anopheles moucheti) or also changes in behavior induced by insecticides applied inside houses, such as the well-known deterrent effect of permethrin-treated nets or the irritant effect of DDT. The use of insecticides may change the composition of local Anopheles populations, such as A. arabiensis taking up the place of A. gambiae in Senegal, A. aquasalis replacing A. darlingi in Guyana, or A. harrisoni superseding A. minimus in Vietnam. The change in behavior, such as biting activity earlier than usually reported-for example, Anopheles funestus after a large-scale distribution of long-lasting insecticidal nets-or insecticide resistance, in particular the current spread of pyrethroid resistance, could hamper the efficacy of classic pyrethroid-treated long-lasting insecticidal nets and maintained transmission. These issues must be well documented in every situation to elaborate, implement, monitor, and evaluate tailored vector control programs, keeping in mind that they must be conceived as integrated programs with several well and appropriately coordinated approaches, combining entomological but also parasitological, clinical, and social methods and analyses. A successful integrated vector control program must then be designed to reduce transmission and incidence rates of malaria morbidity and overall mortality.
... albopictus. The results in contact and noncontact trials indicated that escape responses of mosquitoes to β-caryophyllene oxide were significantly greater than with DEET, similar to the previous study by Nararak et al. (2019) in which β-caryophyllene oxide was tested at concentrations of 0.1, 0.25, 0.5 and 1.0% (v/v) against Ae. aegypti and An. ...
... The PPO and its leaf powder show insecticidal effect against T. castaneum may be reverted to astringent properties of tannins in the fruit peel, that prevents insect's infestation (Hamouda et al., 2014,N irjara et al., 2010). Also, Caryophyllene and caryophyllene oxide were the main components of PPO and TTO, which is recognized among sesquiterpenes as a strong repellent against T. castaneum (Nararak et al. 2019). This contradiction in the essential oil composition may be a function of to many environmental factors influencing the cultivation of plant, geographical origin, genetic factors, storage, part of the plant, the season it is collected in, and the distillation procedure. ...
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Three essential oils of Melaleuca alternifolia (tea tree oil), Vitis vinifera (grapes seeds oil), and Punica granatum (pomegranate fruit peel oil) were tested for their antifeedant activity against the rice weevil, Sitophilus oryzae (L.). Moreover, the nanoemulsion formulations of these oils were prepared and their potential applications in controlling stored product insect were evaluated. The chemical constituents of the isolated oils were identified by gas chromatography/mass spectrometry (GC-MS). However, the main components of Melaleuca alternifolia (TTO) were: Patchouli alcohol (39.16%), 2-Caren-10-al (27.7%), Caryophyllene oxide (15.03%), and Caryophyllene (14.3%). While Punica granatum fruit peel oil (PPO) were: linoleic-acid (29.33%), D-Limonene (13.79%), Caryophyllene (13.9%), cis-Vaccenic acid (12.66%), and squalene (9.12%) , and Vitis vinifera seeds (GPO) was: Limonene (80.0%). The antifeedant effect of these essential oils was estimated against the rice weevil, Sitophilus oryzae (L.). various experiments were prepared to measure the nutritional indices such as feeding deterrence index (FDI), relative growth rate (RGR), relative consumption rate (RCR), and efficiency of conversion of ingested food (ECI). (FDI) increases with increasing oil concentration. As a result, the TTO and PPO achieved FDI 89.59 and 85.83 at a concentration of 2000mg/g. same concentration (2000mg/g) of TTO decreased (RGR) to 0.66 mg/g in comparison with 14.04 in control. In general, all tested oils considerably reduced the feeding of the insect. Two nanoemulsions (A and B) of essential oils TTO, PPO, and GPO were prepared by a concentration of (4%). The oil and surfactant were used in different two ratios, 1:1 and 1:1.5 (v/v), and subjected to different sonication times (30 and 45 mins). All nanoemulsions were found to be stable after different physicochemical and stability studies such as centrifugation and thermodynamic (heating and cooling, freezing, and thawing stress) except Formulation TTO (B) which was unstable. Besides, all these emulsion preparations were in the nanometric size ranged from 247.6 to 53.25nm. However, the particle size decreases with increasing both surfactant concentration and sonication time. Furthermore, the high stability of GPO (A) and PPO (A) could be due to the great zeta potential, which was -36.7 and -31.0 mV. The formulated nanoemulsion showed high insecticidal activity more than its essential oils against Sitophilus oryzae. Moreover, nanoemulsions (B) of all tested emulsions were more toxic than nanoemulsions (A). The relative potency of PPO (B) increased than its oil by 12.22 fold. Also, the toxicity of GPO nanoemulsion (A, B) increased by 4.20 and 6.07 fold than GPO.
... aegypti. (USDA strain) and Anopheles minimus (KU strain) mosquitoes, performing better than the commercial repellent N,N-diethyl-meta-toluamide (DEET) (Nararak et al., 2019). Caryophyllene oxide, which is a main component also of the Origanum vulgare L. EO, led to 100 % repellence against Tribolium castaneum (Herbst) beetles when tested at 0.03 mg cm −2 (Kim et al., 2010). ...
Article
Stevia rebaudiana (Asteraceae) is a medicinal plant of economic importance in the food market for the manufacture of natural sweeteners, namely steviol glycosides. The plant biomass used on an industrial level may also be the source of an essential oil (EO) of potential interest for developing novel insecticides. Here, the leaf EO chemical composition of S. rebaudiana growing in central Italy was analysed by gas chromatography-mass spectrometry (GC–MS). The EO insecticidal efficacy was evaluated against the aphid Metopolophium dirhodum (Hemiptera: Aphididae), a major pest of cereals. The EO composition was dominated by sesquiterpenes, i.e. caryophyllene oxide (20.7 %), spathulenol (14.9 %) and (E)-nerolidol (8.0 %), and diterpenes, i.e. phytol (9.2 %). The EO was effective against M. dirhodum aphids, showing an LC50(90) of 5.1 and 10.8 mL L⁻¹, respectively. The efficacy of the EO major constituents, namely caryophyllene oxide, spathulenol, (E)-nerolidol and phytol was also tested against M. dirhodum. Phytol was the most effective aphicide (LC50(90) = 1.4(4.2) mL L⁻¹), followed by (E)-nerolidol (LC50(90) = 3.5(9.3) mL L⁻¹) and spathulenol (LC50(90) = 4.3(7.5) mL L⁻¹). The EO was minimally toxic towards non-target Eisenia fetida adults and Harmonia axyridis larvae and adults. Overall, phytol, (E)-nerolidol and spathulenol can be considered further for developing effective and eco-friendly green insecticides against aphids.
... However, in the current study, chemical analysis of three specimens (CIA-1-CIA-3) identified moderate amounts of β-caryophyllene oxide (2.4-7.3%; Table 2), which is a potent mosquito repellent [34] and may also be a fly repellent. Due to the high yield of volatiles of this species, a moderate relative percentage of β-caryophyllene oxide effectively gives a high net yield, making this observation plausible. ...
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The highly aromatic Australian mint bushes from the genus Prostanthera Labill. produce a high yield of essential oil on hydrodistillation. Together with its rich history, horticultural potential, iconic flowers, and aromatic leaves, it achieves high ornamental and culinary value. Species in the genus express highly diverse and chemically unique essential oils that demonstrate intra-and inter-specific patterns that have inspired taxonomic reinterpretation for over a hundred years. Previous studies have conveyed that phenoplastic expression of volatiles creates chemotypes within taxa, adding complexity to chemophenetic exploration. The current study chemically characterised essential oils from 64 highly aromatic specimens, representative of 25 taxa, giving yields as high as >2% g/g. The chemical profiles of essential oils are diverse, but generally include 1,8-cineole and signatory compounds such as sesquiterpene oxides, caryophyllene oxide, kessane and cis-dihydroagarofuran; sesquiterpene alcohols, globulol, epiglobulol, maaliol, prostantherol, spathulenol and ledol; and monoterpene derivatives of common scaffolds, borneol, bornyl acetate, bornanone, linalool and linalyl acetate. As in previous studies, analysis of chemical data confirms that the chemistry strongly agrees with taxonomic classifications. Importantly, as in classical taxonomy, the current chemical study complemented morphological analysis but conveys chemovariation, obscuring the taxonomic agreement. Nevertheless, variation within taxa may be due to environmental factors, meaning that cultivation of species in gardens will create different chemical profiles as compared to those published here.
... Aedes aegypti, Cx. quinquefasciatus and An. minimus were uniformly reared under insectary-controlled conditions (25 • C ± 5 • C, 80% ± 10% RH, and 12:12 light:dark photoperiod) at the Department of Entomology, Faculty of Agriculture, Kasetsart University, following previously described methods [30][31][32]. ...
Article
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Several types of olfactometers have been used to evaluate mosquito responses to agents that mimic natural volatiles that repel or attract. The Y-tube olfactometer has been widely used to study repellents and attractants, while the high-throughput screening system assay has only been used to study repellents. Whether the high-throughput screening system assay is suitable for evaluating attractants is unknown. We evaluated the responses to four lactic-acid-based mixtures and two non-lactic-acid-based chemical lure candidates using the high-throughput screening system (HITSS) for three mosquito species (laboratory strains and field populations of both Aedes aegypti (L.) and Culex quinquefasciatus Say.; laboratory strain of Anopheles minimus Theobald) under laboratory-controlled conditions. HITSS assay results showed that KU-lure #1 elicited the greatest percent attraction for pyrethroid-resistant and -susceptible Ae. aegypti. KU-lure #6 elicited the strongest attractive response for pyrethroid-susceptible and -resistant Cx. quinquefasciatus and pyrethroid-susceptible An. minimus. The response to the lures from each species was independent of the pyrethroid susceptibility status (Ae. aegypti, p = 0.825; Cx. quinquefasciatus, p = 0.056). However, a significant difference in attraction to KU-lure #6 was observed between diurnal and nocturnal mosquitoes (Cx. quinquefasciatus vs. Ae. aegypti, p = 0.014; An. minimus vs. Ae. aegypti, p = 0.001). The laboratory-level HITSS assay effectively selects potential lure candidates. Because the host-seeking behavior differs between mosquito species, further studies are needed to develop species-specific attractants. Additional studies in semi-field screen houses using commercial traps are necessary to evaluate the accuracy of these laboratory assay results.
... Large amounts of this compound have also been identified in oil from L. maculatum aerial parts [109]. This component exhibits antimicrobial [85], antifungal [110], and insecticidal properties [111,112] and induces apoptosis of neoplastic cells [113]. ...
Article
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The aim of this study was to conduct a histochemical analysis to localize lipids, terpenes, essential oil, and iridoids in the trichomes of the L. album subsp. album corolla. Morphometric examinations of individual trichome types were performed. Light and scanning electron microscopy techniques were used to show the micromorphology and localization of lipophilic compounds and iridoids in secretory trichomes with the use of histochemical tests. Additionally, the content of essential oil and its components were determined using gas chromatography-mass spectrometry (GC-MS). Qualitative analyses of triterpenes carried out using high-performance thin-layer chromatography (HPTLC) coupled with densitometric detection, and the iridoid content expressed as aucubin was examined with spectrophotometric techniques. We showed the presence of iridoids and different lipophilic compounds in papillae and glandular and non-glandular trichomes. On average, the flowers of L. album subsp. album yielded 0.04 mL/kg of essential oil, which was dominated by aldehydes, sesquiterpenes, and alkanes. The extract of the L. album subsp. album corolla contained 1.5 × 10−3 ± 4.3 × 10−4 mg/mL of iridoid aucubin and three triterpenes: oleanolic acid, β-amyrin, and β-amyrin acetate. Aucubin and β-amyrin acetate were detected for the first time. We suggest the use of L. album subsp. album flowers as supplements in human nutrition.
... The (E)-caryophyllene, at a lower content (2.35%), was found in the essential oil of the EflB specimen. Studies report that caryophyllene oxide has insecticidal activity against the Aedes aegypt vector, an important vector of diseases such as dengue, zika and chikungunya [39]. This compound also presents gastroprotective potential [40] and antiviral potential [41], as well as potential activity against leishmania [42]. ...
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Eugenia florida DC. belongs to the Myrtaceae family, which is present in almost all of Brazil. This species is popularly known as pitanga-preta or guamirim and is used in folk medicine to treat gastrointestinal problems. In this study, two specimens of Eugenia florida (Efl) were collected in different areas of the same region. Specimen A (EflA) was collected in an area of secondary forest (capoeira), while specimen B (EflB) was collected in a floodplain area. The essential oils (EOs) were extracted from both specimens of Eugenia florida by means of hydrodistillation. Gas chromatography coupled to mass spectrometry (GC/MS) was used to identify the volatile compounds present, and the antioxidant capacity of the EOs was determined by antioxidant capacity (AC-DPPH) and the Trolox equivalent antioxidant (TEAC) assay. For E. florida, limonene (11.98%), spathulenol (10.94%) and α-pinene (5.21%) were identified as the main compounds of the EO extracted from sample A, while sample B comprised selina-3,11-dien-6α-ol (12.03%), eremoligenol (11.0%) and γ-elemene (10.70%). This difference in chemical composition impacted the antioxidant activity of the EOs between the studied samples, especially in sample B of E. florida. This study is the first to report on the antioxidant activity of Eugenia florida DC. essential oils.
... In clove oil, eugenol is the primary component that also has a repellent effect against insects [17]. In comparison, cubeb piper has β-caryophyllene as a primary component that has repellent activity [18,19]. However, due to its high volatility, essential oil application is limited as an insecticide [20]. ...
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The Indo-Malayan drywood termite, Cryptotermes cynocephalus (Light) (Kalotermitidae), is considered one of the most invasive drywood termites in the Southeast Asian region. Once infesting a timber, the colony of a drywood termite is very difficult to be controlled. Thus, the best way to mitigate a new infestation of a drywood termite is by applying chemical protection on wood. In recent years, particular attention has been given by researchers to develop and use organic termiticides, such as essential oils extracted from plants as active ingredients. The objective of the present study is to evaluate the repellency performance of several economically important essential oils from Indonesia, such as Clove (Eugenia caryophyllata), Cubeb Pepper (Piper cubeba L), and Lemon Grass (Cymbopogon winterianus Jowitt ) against a drywood termite, C. cynocephalus . The test was performed by subjecting various concentrations of essential oil toward C. cynocephalus in the force-feeding test method. Sample weight-loss was evaluated after two weeks test. The results suggested that Clove oil has the highest repellence performance against C. cynocephalus , followed by Lemon Grass and Cubeb Pepper oils. The Termite mortality rate was also recorded to understand the toxicity performance of those essential oils.
... Caryophyllene and its derivatives (present in clove essential oil) possess repellent activity against Ae. aegypti (Nararak et al. 2019) and other insects (Sun et al. 2020). Other compounds present in rosemary essential oils have been tested as good repellents against insects (Lim et al. 2019;Sun et al. 2020). ...
Article
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Essential oils have been tested as insect repellents with moderate results. The most important characteristics of these oils are that they possess a high chemical diversity of compounds, are cheap, and are easily accessible. Recently, mixtures of essential oils have shown a higher repellent activity than a single essential oil, probably by increasing the effectiveness with the number of chemicals in the mixture. The repellent effect of essential oils from citronella (Cymbopogon nardus), mint (Mentha arvensis), rosemary (Rosmarinus officinalis L.), clove (Eugenia caryophyllata), and their mixture was evaluated against Aedes aegypti. The mixture of citronella, mint, and clove essential oils (1:1:1) was also evaluated in an adulticidal bioassay. Additionally, chemical identification was performed using these commercial essential oils. The 1:1:1 mixture of citronella, mint, and clove essential oils was as effective as the commercial repellent DEET at lower doses (5%), and it is a good candidate for an adulticide at higher doses (20–25%). The chemical constituents of the essential oils were mostly terpenes and oxygenated terpenoids. These findings were discussed in terms of economic and environmental frameworks.
... During 2016-2020, studies were conducted on plantbased mosquito repellents [26,[57][58][59] in the SFS enclosure at MFRS. Evaluation of a binary mixture of β-caryophyllene (BCO) and an essential oil (EO) applied on two collectors positioned at the opposite end of the SFS showed that BCO-EO repellent provided a protective time against laboratory-reared Aedes aegypti bites for 4.7 h. ...
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Additional vector control tools are needed to supplement current strategies to achieve malaria elimination and control of Aedes -borne diseases in many settings in Thailand and the Greater Mekong Sub-region. Within the next decade, the vector control community, Kasetsart University (KU), and the Ministry of Higher Education, Science, Research and Innovation must take full advantage of these tools that combine different active ingredients with different modes of action. Pu Teuy Mosquito Field Research Station (MFRS), Department of Entomology, Faculty of Agriculture, Kasetsart University (KU), Thailand was established in 2001 and has grown into a leading facility for performing high-quality vector biology and control studies and evaluation of public health insecticides that are operationally relevant. Several onsite mosquito research platforms have been established including experimental huts, a 40-m long semi-field screening enclosure, mosquito insectary, field-laboratory, and living quarters for students and researchers. Field research and assessments ranged from ‘basic’ investigations on mosquito biology, taxonomy and genetics to more ‘applied’ studies on responses of mosquitoes to insecticides including repellency, behavioural avoidance and toxicity. In the course of two decades, 51 peer-reviewed articles have been published, and 7 masters and 16 doctoral degrees in Entomology have been awarded to national and international students. Continued support of key national stakeholders will sustain MFRS as a Greater Mekong Subregion centre of excellence and a resource for both insecticide trials and entomological research.
... Pupae were collected in a plastic cup containing distilled water. The pupae cup was shifted to the adult cage (30 × 30 × 30 cm) for adult emergence (Nararak et al. 2019). After emergence, adults were fed on 10% sucrose solution. ...
Article
Disease vectoring mosquitoes are a serious threat to humans. However, till today only few mosquito repellents have been identified. The current study was conducted to evaluate the repellent potential of Carpesium abrotanoides essential oil against Aedes aegypti females by human bait technique. Essential oil was extracted by steam distillation process while the identification of chemical constituents was carried out by gas chromatography–mass spectrometry. Time span repellent bioassays of C. abrotanoides essential oil in comparison to DEET were performed at three different doses (33 μg/cm2, 165 μg/cm2, and 330 μg/cm2) under laboratory conditions. Highest repellency periods for essential oil and DEET were observed at the tested dose of 330 μg/cm2 with 315 min and 720 min, respectively. Lowest repellency period of 45 min for essential oil and 105 min for DEET was recorded at the tested dose of 33 μg/cm2. Major constituents caryophyllene (24.3%) and trans-nerolidol (12.0%) of C. abrotanoides essential oil were also evaluated as repellents at three different doses (330 μg/cm2, 165 μg/cm2, and 33 μg/cm2) against Ae. aegypti. Surprisingly, trans-nerolidol completely inhibited Ae. aegypti landings for 45 min when tested at 330 μg/cm2. However, caryophyllene did not completely inhibit Ae. aegypti landing even after immediate application at the tested dose of 330 μg/cm2. At the tested dose of 330 μg/cm2, the mixture (trans-nerolidol + caryophyllene) completely inhibited Ae. aegypti landing for 60 min indicating the synergistic effect of caryophyllene. Hence, C. abrotanoides as well as its major constituent, especially trans-nerolidol, have potential to formulate as mosquito repellent comparable of DEET.
... compounds in the essential oil (Table 1). This chemical profile is similar to that observed in the essential oils of the species P. amalago L., P. umbellatum L., P. dilatatum LC Rich, P. leptorum Kunth, P. amplum Kunth, P. gaudichaudianum Kunth, and P. crassinervium Kunth, which demonstrated significant anti-cancer, anti-inflammatory, anti-bacterial, repellent, anti-fungal, anti-malarial, anti-leishmanial, and larvicidal activities (Guerrini et al. 2009;Andrade et al. 2011;Kelly et al. 2014;Vaz et al. 2016;Ventorim et al. 2016;Ravi et al. 2006;Raphael et al. 2013;Sperotto et al. 2013;Nararak et al. 2019). ...
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The mosquito vectors of the genera Aedes and Anopheles present resistance to several commercial insecticides, which are also toxic to non-predator targets. On the other hand, essential oils are a promising source of insecticides. Thus, in this work, the essential oil from the leaves of Piper purusanum was characterized by gas chromatography–based approaches and evaluated as biodefensive against malaria and dengue vectors. The main compounds of P. purusanum essential oil were β-caryophyllene (57.05%), α-humulene (14.50%), and germacrene D (8.20%). The essential oil inhibited egg hatching (7.6 ± 1.5 to 95.6 ± 4.5%), caused larval death (LC50 from 49.84 to 51.60 ppm), and inhibited the action of acetylcholinesterase (IC50 of 2.29 µg/mL), which can be related to the mechanisms of action. On the other hand, the biological activities of β-caryophyllene, α-humulene, and germacrene D were higher than that of essential oil. In addition, these sesquiterpenes and essential oil did not show a lethal effect on Toxorhynchites splendens, Anisops bouvieri, Gambusia affinis, and Diplonychus indicus (LC50 from 2098.80 to 7707.13 ppm), although D. indicus is more sensitive (SI/PSF from 48.56 to 252.02 ppm) to essential oil, representing a natural alternative against these relevant vectors.
... Recent findings reported that (E)-nerolidol and spathulenol, which were presented as species-specific sesquiterpenoids in S. gigantea EOs, revealed effective allelopathic and insecticidal effects with potential for the developing a new natural pesticide [53][54][55]. Many findings have demonstrated the biological activity of caryophyllene oxide [53,[55][56][57][58] that was a common compound in the presented Solidago spp. EOs. ...
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... Caryophyllene oxide might play an important role for repellent activities of the total oils. Furthermore, Nararak et al. (2019) covered that caryophyllene oxide produced much stronger irritant and repellent properties against Aedes aegypti (L.) and Anopheles minimus (Theobald) than DEET did, which suggested this compound was promising to be an alternative ingredient in viable repellent formulations for mosquito control. ...
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Background Malaria in Southeast Asia frequently clusters along international borders. For example, while most of Thailand is malaria free, the border region shared with Myanmar continues to have endemic malaria. This spatial pattern is the result of complex interactions between landscape, humans, mosquito vectors, and malaria parasites. An understanding of these complex ecological and socio-cultural interactions is important for designing and implementing malaria elimination efforts in the region. This article offers an ecological perspective on the malaria situation along the Thailand–Myanmar border. Discussion This border region is long (2000 km), mountainous, and the environment ranges from thick forests to growing urban settlements and wet-rice fields. It is also a biologically diverse region. All five species of malaria known to naturally infect humans are present. At least three mosquito vector species complexes, with widely varying behavioural characteristics, exist in the area. The region is also a hub for ethnic diversity, being home to over ten different ethnolinguistic groups, several of which have been engaged in conflict with the Myanmar government now for over half a century. Given the biological and ethnic diversity, as well as the complex socio-political context, malaria control and elimination in the region is challenging. Conclusion Despite these complexities, multipronged approaches including collaborations with multiple local organizations, quick access to diagnosis and treatment, prevention of mosquito bites, radical cure of parasites, and mass drug administration appear to be drastically decreasing Plasmodium falciparum infections. Such approaches remain crucial as the region moves toward elimination of P. falciparum and potentially Plasmodium vivax.
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Repellency activity of Thai essential oils derived from ylang ylang (Cananga odorata (Lamk.) Hook.f. & Thomson: Annonaceae) and lemongrass (Cymbopogon citratus (DC.) Stapf: Poaceae) were tested against two mosquito vectors, Aedes aegypti (L.) and Culex quinquefasciatus (Say). There were compared with two chemical repellents (DEET 20% w/w; Sketolene Shield(®) and IR3535, Ethyl butylacetylaminopropionate 12.5% w/w; Johnson's Baby Clear Lotion Anti-Mosquito(®)). Each herbal repellent was applied in 3 diluents; coconut oil, soybean oil and olive oil at 0.33μl/cm(2) on the forearm of volunteers. All herbal repellent exhibited higher repellent activity than IR3535 12.5% w/w, but lower repellent activity than DEET 20% w/w. The C. odorata oil in coconut oil exhibited excellent activity with 98.9% protection from bites of A. aegypti for 88.7±10.4min. In addition, C. citratus in olive oil showed excellent activity with 98.8% protection from bites of C. quinquefasciatus for 170.0±9.0min. While, DEET 20% w/w gave protection for 155.0±7.1min to 182.0±12.2min and 98.5% protection from bites of two mosquito species. However, all herbal repellent provided lower repellency activity (97.4% to 98.9% protection for 10.5min to 88.7min) against A. aegypti than C. quinquefasciatus (98.3% to 99.2% protection for 60min to 170min). Our data exhibited that C. odorata oil and C. citratus oil are suitable to be used as green repellents for mosquito control, which are safe for humans, domestic animals and environmental friendly. Copyright © 2014. Published by Elsevier B.V.
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Knowledge on test conditions that may influence behavioral responses of mosquitoes is critical when excito-repellency tests are conducted. The objective of this study was to investigate the effect of test time differences on normal circadian activity and behavioral responses of field and colonized Aedes aegypti (L.) (=Stegomyia aegypti) and Culex quinquefasciatus Say to DEET, one of the most common synthetic repellent active ingredients available. Two field populations of Ae. aegypti and Cx. quinquefasciatus from Kanchanaburi and Nonthaburi provinces, respectively, and two long-standing laboratory populations, Ae. aegypti obtained from the U.S. Department of Agriculture, and Cx. quinquefasciatus from the Ministry of Public Health, Thailand, were used. Each population was exposed to DEET during two different periods of time (0900-1500 hours) and (2100-0300 hours). Both field and laboratory Cx. quinquefasciatus showed marked differences in spatial repellent escape responses between day and nighttime periods but none in direct contact tests. No significant differences between day and nighttime testing periods were observed with field or laboratory Ae. aegypti, except a higher daytime escape response from noncontact DEET treatment. This study indicates that test time may influence the behavioral avoidance responses and is a potential confounder of excito-repellency evaluations. © 2014 Entomological Society of America.
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Constant and extensive use of chemical insecticides has created a selection pressure and favored resistance development in many insect species worldwide. One of the most important pyrethroid resistance mechanisms is classified as target site insensitivity, due to conformational changes in the target site that impair a proper binding of the insecticide molecule. The voltage-gated sodium channel (NaV) is the target of pyrethroids and DDT insecticides, used to control insects of medical, agricultural and veterinary importance, such as anophelines. It has been reported that the presence of a few non-silent point mutations in the NaV gene are associated with pyrethroid resistance, termed as 'kdr' (knockdown resistance) for preventing the knockdown effect of these insecticides. The presence of these mutations, as well as their effects, has been thoroughly studied in Anopheles mosquitoes. So far, kdr mutations have already been detected in at least 13 species (Anopheles gambiae, Anopheles arabiensis, Anopheles sinensis, Anopheles stephensi, Anopheles subpictus, Anopheles sacharovi, Anopheles culicifacies, Anopheles sundaicus, Anopheles aconitus, Anopheles vagus, Anopheles paraliae, Anopheles peditaeniatus and Anopheles albimanus) from populations of African, Asian and, more recently, American continents. Seven mutational variants (L1014F, L1014S, L1014C, L1014W, N1013S, N1575Y and V1010L) were described, with the highest prevalence of L1014F, which occurs at the 1014 site in NaV IIS6 domain. The increase of frequency and distribution of kdr mutations clearly shows the importance of this mechanism in the process of pyrethroid resistance. In this sense, several species-specific and highly sensitive methods have been designed in order to genotype individual mosquitoes for kdr in large scale, which may serve as important tolls for monitoring the dynamics of pyrethroid resistance in natural populations. We also briefly discuss investigations concerning the course of Plasmodium infection in kdr individuals. Considering the limitation of insecticides available for employment in public health campaigns and the absence of a vaccine able to brake the life cycle of the malaria parasites, the use of pyrethroids is likely to remain as the main strategy against mosquitoes by either indoor residual spraying (IR) and insecticide treated nets (ITN). Therefore, monitoring insecticide resistance programs is a crucial need in malaria endemic countries.
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Chikungunya and dengue viruses emerged in Gabon in 2007, with large outbreaks primarily affecting the capital Libreville and several northern towns. Both viruses subsequently spread to the south-east of the country, with new outbreaks occurring in 2010. The mosquito species Aedes albopictus, that was known as a secondary vector for both viruses, recently invaded the country and was the primary vector involved in the Gabonese outbreaks. We conducted a retrospective study of human sera and mosquitoes collected in Gabon from 2007 to 2010, in order to identify other circulating arboviruses. Sample collections, including 4312 sera from patients presenting with painful febrile disease, and 4665 mosquitoes belonging to 9 species, split into 247 pools (including 137 pools of Aedes albopictus), were screened with molecular biology methods. Five human sera and two Aedes albopictus pools, all sampled in an urban setting during the 2007 outbreak, were positive for the flavivirus Zika (ZIKV). The ratio of Aedes albopictus pools positive for ZIKV was similar to that positive for dengue virus during the concomitant dengue outbreak suggesting similar mosquito infection rates and, presumably, underlying a human ZIKV outbreak. ZIKV sequences from the envelope and NS3 genes were amplified from a human serum sample. Phylogenetic analysis placed the Gabonese ZIKV at a basal position in the African lineage, pointing to ancestral genetic diversification and spread. We provide the first direct evidence of human ZIKV infections in Gabon, and its first occurrence in the Asian tiger mosquito, Aedes albopictus. These data reveal an unusual natural life cycle for this virus, occurring in an urban environment, and potentially representing a new emerging threat due to this novel association with a highly invasive vector whose geographic range is still expanding across the globe.
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With the rapid spread of pyrethroid resistance in the main malaria vectors from Benin and the various resistance mechanisms involved (metabolic resistance and knock-down resistance (kdr), it is important to foresee effective resistance management strategies. Thus, the knowledge of the insensitive acetylcholinesterase (ace-1R) effects on phenotypes of An. gambiae will help us to strengthen basic and operational research on thedevelopment of strategies that will use organophosphates or carbamates as alternatives against pyrethroids-resistant malaria vectors in the field. Larvae and pupae of Anopheles gambiae s.l. mosquitoes were collected from the breeding sites in Ouemé , Atacora, and Alibori departments. CDC susceptibility tests were conducted on unfed female mosquitoes aged 2-5 days old. CDC bioassays were performed with stock solutions of fenitrothion (50 μg per bottle) and bendiocarb (12.5 μg per bottle). PCR techniques were used to detect species and Ace-1 mutations. Anopheles gambiae Seme and Kandi populations were susceptible to fenitrothion whereas Anopheles gambiae Tanguieta and Malanville populations were resistant. An. gambiae populations from Seme, Kandi and Malanville were fully susceptible to bendiocarb whereas those from Tanguieta have developed a strong resistance to the same insecticide. A slight decrease in mortality rate was observed with 97.91% in populations of mosquitoes from Malanville. PCR revealed that all specimens tested were Anopheles gambiae s.s.. This study demonstrated the need to monitor organophosphate (OPs) and Carbamates resistance among populations of the An. gambiae s.l. in Benin, to determine its spread and anticipate vector control failure where these insecticides are used. However, further studies are needed to understand the current distribution of the Ace-1R mutation in other localities in the south-north transect Benin.
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Physiological resistance and behavioral responses of mosquito vectors to insecticides are critical aspects of the chemical-based disease control equation. The complex interaction between lethal, sub-lethal and excitation/repellent ('excito-repellent') properties of chemicals is typically overlooked in vector management and control programs. The development of "physiological" resistance, metabolic and/or target site modifications, to insecticides has been well documented in many insect groups and disease vectors around the world. In Thailand, resistance in many mosquito populations has developed to all three classes of insecticidal active ingredients currently used for vector control with a majority being synthetic-derived pyrethroids. Evidence of low-grade insecticide resistance requires immediate countermeasures to mitigate further intensification and spread of the genetic mechanisms responsible for resistance. This can take the form of rotation of a different class of chemical, addition of a synergist, mixtures of chemicals or concurrent mosaic application of different classes of chemicals. From the gathered evidence, the distribution and degree of physiological resistance has been restricted in specific areas of Thailand in spite of long-term use of chemicals to control insect pests and disease vectors throughout the country. Most surprisingly, there have been no reported cases of pyrethroid resistance in anopheline populations in the country from 2000 to 2011. The precise reasons for this are unclear but we assume that behavioral avoidance to insecticides may play a significant role in reducing the selection pressure and thus occurrence and spread of insecticide resistance. The review herein provides information regarding the status of physiological resistance and behavioral avoidance of the primary mosquito vectors of human diseases to insecticides in Thailand from 2000 to 2011.
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This systematic review elaborates the concepts and impacts of border malaria, particularly on the emergence and spread of Plasmodium falciparum and Plasmodium vivax multidrug resistance (MDR) malaria on Thailand-Myanmar and Thailand-Cambodia borders. Border malaria encompasses any complex epidemiological settings of forest-related and forest fringe-related malaria, both regularly occurring in certain transmission areas and manifesting a trend of increased incidence in transmission prone areas along these borders, as the result of interconnections of human settlements and movement activities, cross-border population migrations, ecological changes, vector population dynamics, and multidrug resistance. For regional and global perspectives, this review analyzes and synthesizes the rationales pertaining to transmission dynamics and the vulnerabilities of border malaria that constrain surveillance and control of the world's most MDR falciparum and vivax malaria on these chaotic borders.
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Background To control malaria in Tanzania, two primary vector control interventions are being scaled up: long-lasting insecticide-treated nets (LLINs) and indoor residual spraying (IRS). The main threat to effective malaria control is the selection of insecticide resistance. While resistance to pyrethroids, the primary insecticide used for LLINs and IRS, has been reported among mosquito vectors in only a few sites in Tanzania, neighbouring East African countries are recording increasing levels of resistance. To monitor the rapidly evolving situation, the resistance status of the malaria vector Anopheles gambiae s.l to different insecticides and the prevalence of the kdr resistance allele involved in pyrethroid resistance were investigated in north-western Tanzania, an area that has been subject to several rounds of pyrethroid IRS since 2006. Methods Household collections of anopheline mosquitoes were exposed to diagnostic dosages of pyrethroid, DDT, and bendiocarb using WHO resistance test kits. The relative proportions of An. gambiae s.s and Anopheles arabiensis were also investigated among mosquitoes sampled using indoor CDC light traps. Anophelines were identified to species and the kdr mutation was detected using real time PCR TaqMan assays. Results From the light trap collections 80% of An. gambiae s.l were identified as An. gambiae s.s and 20% as An. arabiensis. There was cross-resistance between pyrethroids and DDT with mortality no higher than 40% reported in any of the resistance tests. The kdr-eastern variant was present in homozygous form in 97% of An. gambiae s.s but was absent in An. arabiensis. Anopheles gambiae s.s showed reduced susceptibility to the carbamate insecticide, bendiocarb, the proportion surviving WHO tests ranging from 0% to 30% depending on season and location. Conclusion Anopheles gambiae s.s has developed phenotypic resistance to pyrethroids and DDT and kdr frequency has almost reached fixation. Unlike in coastal Tanzania, where the ratio of An. gambiae s.s to An. arabiensis has decreased in response to vector control, An. gambiae s.s persists at high frequency in north-western Tanzania, probably due to selection of pyrethroid resistance, and this trend is likely to arise in other areas as resistance spreads or is subject to local selection from IRS or LLINs.
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Background The national Global Fund-supported malaria (GFM) program in Thailand, which focuses on the household-level implementation of vector control via insecticide-treated nets (ITNs)/long-lasting insecticidal nets (LLINs) combined with indoor residual spraying (IRS), has been combating malaria risk situations in different provinces with complex epidemiological settings. By using the perception of malaria villagers (MVs), defined as villagers who recognized malaria burden and had local understanding of mosquitoes, malaria, and ITNs/LLINs and practiced preventive measures, this study investigated the predictors for malaria that are associated with rubber plantations in an area of high household-level implementation coverage of IRS (2007–2010) and ITNs/LLINs (2008–2010) in Prachuap Khiri Khan Province. Methods A structured questionnaire addressing socio-demographics, household characteristics and health behavioral factors (knowledge, perceptions and practices) regarding the performed interventions was administered to the 313 households (70 malaria-affected and 243 malaria-unaffected) that had respondents aged ≥18 years of both genders. In the univariate and multivariate analyses, only 246 (78.6%) MV respondents (62 malaria-affected and 184 malaria-unaffected) were analyzed to determine the predictors for risk (morbidity). Results The majority (70%) of households were covered by IRS. For a combination of ITNs/LLINs, there were 74% of malaria-affected households covered and 46% of malaria-unaffected households. In a logistic regression analysis using odds ratios (aORs) adjusted on the variables and a 95% confidence interval (CI), malaria affecting MVs was associated with daily worker (i.e., earning daily income by normally practicing laborious activities mostly in agriculture such as rubber tapping and rubber sheet processing at the smallholdings of rubber plantations) (aOR = 2.9, 95% CI: 1.1-7.4), low-moderate level of malaria knowledge (aOR = 2.4, 95% CI: 1.1-5.0) and sleeping under mosquito-nets (nets/ITNs/LLINs intermittently and ITNs/LLINs only) (aOR = 2.0, 95% CI: 1.0-3.7). Conclusions The MV predictors for malaria-association with rubber plantations included occupation (daily worker), misconceptions about malaria (mosquito and prevention) and the use of mosquito-nets. Human practices such as revisiting rubber plantations while exposed to multiple bites at multiple locations are more likely to apply to daily workers than to rubber farmers/tappers and others. The promotion and use of ITNs/LLINs depends substantially on cultural factors and defensive behaviors relevant to their occupational risk despite the perceived threats of malaria and the perceived benefits of ITNs/LLINs. This information supports the conclusion that GFM program implementation in Thailand or elsewhere for malaria-associated with rubber plantations would benefit from the potential use of ITNs/LLINs and changes in personal protection behaviors.
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Human malaria has been known to be caused by 4 Plasmodium species, with Plasmodium falciparum causing the most-severe disease. Recently, numerous reports have described human malaria caused by a fifth Plasmodium species, Plasmodium knowlesi, which usually infects macaque monkeys. Hundreds of human cases have been reported from Malaysia, several cases have been reported in other Southeast Asian countries, and a few cases have been reported in travelers visiting these areas. Similarly to P. falciparum, P. knowlesi can cause severe and even fatal cases of disease that are more severe than those caused by the other Plasmodium species. Polymerase chain reaction is of value for diagnosis because P. knowlesi infection is easily misdiagnosed as less dangerous Plasmodium malariae infection with conventional microscopy. P. knowlesi infection should be suspected in patients who are infected with malaria in Southeast Asia. If human–mosquito–human transmission were to occur, the disease could spread to new areas where the mosquito vectors live, such as the popular tourist areas in western India.
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Plant-based repellents have been used for generations in traditional practice as a personal protection measure against host-seeking mosquitoes. Knowledge on traditional repellent plants obtained through ethnobotanical studies is a valuable resource for the development of new natural products. Recently, commercial repellent products containing plant-based ingredients have gained increasing popularity among consumers, as these are commonly perceived as "safe" in comparison to long-established synthetic repellents although this is sometimes a misconception. To date insufficient studies have followed standard WHO Pesticide Evaluation Scheme guidelines for repellent testing. There is a need for further standardized studies in order to better evaluate repellent compounds and develop new products that offer high repellency as well as good consumer safety. This paper presents a summary of recent information on testing, efficacy and safety of plant-based repellents as well as promising new developments in the field.
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The mosquito repellent activity of 38 essential oils from plants at three concentrations was screened against the mosquito Aedes aegypti under laboratory conditions using human subjects. On a volunteer's forearm, 0.1 mL of oil was applied per 30 cm2 of exposed skin. When the tested oils were applied at a 10% or 50% concentration, none of them prevented mosquito bites for as long as 2 h, but the undiluted oils of Cymbopogon nardus (citronella), Pogostemon cablin (patchuli), Syzygium aromaticum (clove) and Zanthoxylum limonella (Thai name: makaen) were the most effective and provided 2 h of complete repellency. From these initial results, three concentrations (10%, 50% and undiluted) of citronella, patchouli, clove and makaen were selected for repellency tests against Culex quinquefasciatus and Anopheles dirus. As expected, the undiluted oil showed the highest protection in each case. Clove oil gave the longest duration of 100% repellency (2–4 h) against all three species of mosquito. Copyright
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In laboratory tests, ethyl acetate extracts of Hyptis suaveolens Poit. from Guinea-Bissau and Rhododendon tomentosum (Stokes) H. Harmaja (formerly Ledum palustre L.) and Myrica gale L. significantly reduced probing activity of Aedes aegypti (L.). In the field in southern Sweden, extracts of leaves of R. tomentosum, M. gale, and Achillea millefolium L. significantly reduced biting by Aedes mosquitoes. Volatile compounds from M. gale, R. tomentosum, A. millefolium, and H. suaveolens were collected by solid phase microextraction (SPME). Alternatively, compounds in the plants were subjected to extraction by organic solvents of different polarities or by steam distillation and collection by SPME. Compounds collected were identified by gas chromatography-mass spectrometry. Leaves of H. suaveolens contained mainly beta-caryophyllene, bergamotene, and terpinolene. The volatile fraction of an ethyl acetate extract of H. suaveolens was collected by SPME and included beta-caryophyllene, (-) -sabinene, beta-pinene, limonene, alpha-pinene, and bergamotene. The main volatiles detected were alpha-pinene, alpha-phellandrene, myrcene, and limonene from M. gale leaves or inflorescences; pcymene, sabinene, and terpinyl acetate from leaves of R. tomentosum; and (-)-germacrene D, beta-pinene, sabinene, and alpha-pinene from A. millefolium leaves or inflorescences. The selected plant species contained numerous volatiles known to have insecticidal, acaricidal, "pesticidal," and/ or insect repellent properties.
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Immature stages of Aedes aegypti and Ae. albopictus were collected from 17 dengue re-epidemic areas in Chiang Mai and Lampang Provinces, in the north of Thailand. They were reared to adults and tested for dengue viral RNA by a nucleic acid sequence based amplification assay (NASBA). Of a total of 9,825 Ae. aegypti and 150 Ae. albopictus examined, none of them were found positive for the virus, suggesting that transovarial transmission may be very low in the vector populations and may not play a significant role in the epidemiology of dengue infection in Thailand.
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In China, the malaria elimination program was launched in 2010 with the objective to eliminate this disease by 2020. Large-scale malaria control and elimination actions have been conducted with significant success since inception of the nationwide program. The incidence of locally acquired malaria has declined sharply along with the concomitant decrease of malaria-endemic areas from 762 counties reporting malaria in 2010 to just two counties adjacent to border areas (Yunnan, China-Myanmar and Tibet, China-India) in 2016. In total, 1723 counties (79%) and 134 prefectures (52%) had completed the malaria elimination internal assessment by the end of 2016. The year 2017 was the first year without report of indigenous malaria cases throughout the country. Hence, this chapter is meant to share the lessons learned from malaria elimination in China benefiting countries on the way to malaria elimination.
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Pyrethroids are commonly used insecticides in malaria control programs; however, insecticide resistance limits the benefits gained by using these insecticides. In the present study, we assessed the resistance status for different pyrethroids of the malaria mosquito vector, Anopheles stephensi Liston (Diptera: Muscidae), in the Punjab province, Pakistan. Bioassays were conducted using diagnostic doses following standard World Health Organization protocols: 0.05% λ-cyhalothrin, 0.75% permethrin, 0.15% cyfluthrin, 0.05% deltamethrin, and 0.1% cypermethrin. Field collected An. stephensi from four localities in Punjab (Khanewal, Multan, Lodhran, and Bahawalpur) were reared in the laboratory, and non-blood-fed females were used in the bioassays. An. stephensi from all the study sites except Khanewal were found to be susceptible to permethrin and deltamethrin. Resistance or potential resistance to cypermethrin, λ-cyhalothrin and cyfluthrin was observed from all the study sites. The median and 95% knockdown times (KDT50 and KDT95) estimates for all the tested insecticides also showed similar responses. In conclusion, the study revealed resistance to selected pyrethroids in An. stephensi from some parts of Punjab, Pakistan, underscoring the need to devise a resistance management strategy for effective control of this important malaria vector.
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The behavioral responses of colony populations of Aedes aegypti, Aedes albopictus, Culex quinquefasciatus, and Anopheles minimus to four essential oils (citronella, hairy basil, catnip, and vetiver), two standard repellents (DEET and picaridin), and two synthetic pyrethroids (deltamethrin and permethrin) were conducted in the laboratory using an excito-repellency test system. Results revealed that Cx. quinquefasciatus and An. minimus exhibited much stronger behavioral responses to all test compounds (65-98% escape for contact, 21.4-94.4% escape for non-contact) compared to Ae. aegypti (3.7-72.2% escape (contact), 0-31.7% (non-contact)) and Ae. albopictus (3.5-94.4% escape (contact), 11.2-63.7% (non-contact)). In brief, essential oil from vetiver elicited the greatest irritant responses in Cx. quinquefasciatus (96.6%) and An. minimus (96.5%) compared to the other compounds tested. The synthetic pyrethroids caused a stronger contact irritant response (65-97.8% escape) than non-contact repellents (0-50.8% escape for non-contact) across all four mosquito species. Picaridin had the least effect on all mosquito species. Findings from the current study continue to support the screening of essential oils from various plant sources for protective properties against field mosquitoes. © 2014 The Society for Vector Ecology.
Article
Aedes (Stegomyia) aegypti is considered to be the most important dengue vector worldwide. Studies were conducted to design and evaluate a chemically-based baited ovitrap for monitoring Ae. aegypti under laboratory conditions. Several known chemical attractants and three types of ovitraps (ovitraps A, B, and C) were evaluated throughout the oviposition bioassays. Oviposition responses of gravid female Ae. aegypti were evaluated to n-heneicosane, 3-methylindole (skatole), 4-methylphenol (p-cresol), and phenol. Female Ae. aegypti were attracted to all the evaluated compounds. Among them, n-heneicosane at a concentration of 10 ppm (mg/l), skatole from 50 to 1000 ppm, p-cresol at 100 ppm, and phenol at 50 ppm showed a significant positive oviposition response. A blend of the four chemical attractants increased the oviposition response; 67% of the eggs were deposited in the treatment compared to the control. Female Ae. aegypti were significantly more attracted to ovitrap A loaded with the four-component synthetic blend compared to the standard ovitrap in the oviposition bioassays. The compound used in ovitrap A retained its attractant property for up to three days. The chemically-based baited ovitrap may be considered as an option to be integrated during the monitoring of dengue virus vectors in México.
This study investigated insect bite protection and length of the protection with 30 repellents which were divided into 3 categories: plant oil, essential oil and essential oil with ethyl alcohol, tested against three mosquito species, Aedes aegypti, Anopheles minimus and Culex quinquefasciatus, under laboratory conditions. The plant oil group was comprised of Phlai (Zingiber cassumunar) and Sweet basil (Ocimum basilicum). Both substances were effective as repellents and feeding deterrents against An. minimus (205 minutes protection time and a biting rate of 0.9%), Cx. quinquefasciatus (165 minutes protection time and 0.9% biting rate) and Ae. aegypti (90 minutes protection time and 0.8% biting rate). Essential oil from citronella grass (Cymbopogon nardus) exhibited protection against biting from all 3 mosquito species: for An. minimus, Cx. quinquefasciatus and Ae. aegypti, the results were 130 minutes and 0.9%, 140 minutes and 0.8%, and 115 minutes and 0.8%, respectively. The period of protection time against Ae. aegypti for all repellent candidates tested was lower than the Thai Industrial Standards Institute (TISI) determined time of greater than 2 hours.
Article
Bioassay-directed fractionation of clove terpenes from the plant Eugenia caryophyllata has led to the isolation of the following five active known compounds: beta-caryophyllene [1], beta-caryophyllene oxide [2], alpha-humulene [3], alpha-humulene epoxide I [4], and eugenol [5]. Their structures were determined on the basis of spectral analysis (hreims, 1H and 13C nmr). These compounds showed significant activity as inducers of the detoxifying enzyme glutathione S-transferase in the mouse liver and small intestine. The ability of natural anticarcinogens to induce detoxifying enzymes has been found to correlate with their activity in the inhibition of chemical carcinogenesis. Thus, these sesquiterpenes show promise as potential anticarcinogenic agents.
Article
A new test system that includes an excito-repellency test box, test procedures, and statistical treatment of data is described. The method consists of enclosing 25 mosquitoes in an exposure chamber lined with insecticide-treated or untreated (control) test papers. Each chamber has a single portal for mosquitoes to escape to a receiving cage, and numbers escaping are manually recorded at 1-min intervals. The exposure chamber accommodates a screened, 2nd chamber that, when placed in the exposure chamber, prevents the mosquitoes from making physical contact with test papers. A full assay utilized one exposure chamber that permits physical contact with insecticide-treated papers, one chamber that permits physical contact with control papers, one chamber that prevents physical contact with insecticide-treated papers, and a 4th chamber that prevents contact with control papers. After insecticide exposure, test populations are held for observations on 24-h mortalities. A survival analysis approach is described for estimating mosquito escape rates and for comparing differences in mosquito escape rates, with or without physical contact with insecticide, among populations, insecticides, and doses of insecticide.
Article
This study compared the behavioral avoidance responses of 4 mosquito malaria vectors, Anopheles minimus, Anopheles dirus, Anopheles maculatus form B, and Anopheles swadiwongporni, to deltamethrin, the primary insecticide used for indoor residual spraying for malaria vector control in Thailand. Six test populations. representing 4 laboratory colonies and 2 wild-caught populations, were observed during and after exposure to deltamethrin at the operational dose (0.02 g active ingredient/m2) in excito-repellency escape chambers. The laboratory colonies included a deltamethrin-susceptible colony and a deltamethrin-resistant colony of An. minimus species A, 1 colony of An. dirus species B, and 1 colony of An. maculatus form B. The 2 wild-caught populations included An. swadiwongporni and members of the An. dirus complex. Times to escape by female mosquitoes during 30 min of exposure to deltamethrin-treated papers were observed in all populations and compared to nontreated paired controls in contact and noncontact test configurations. Strong behavioral avoidance was observed in the deltamethrin-resistant colony of An. minimus, followed by An. swadiwongporni and An. maculatus. The slowest escape response was observed in the colony of An. dirus species B. All 6 populations of Anopheles showed marked contact irritancy to deltamethrin compared to paired controls and noncontact repellency trials, in both controlled laboratory colonies and field-caught populations. The degree of repellency was less profound than irritancy but, in most cases, produced a significant escape response compared to paired controls. Avoidance behavior appears to be an innate behavior of mosquitoes, as indicated by the general avoidance response detected in all 4 species, regardless of deltamethrin susceptibility status, age, or nutritional and physiological status. Excito-repellency assays of the type described in this study should become an integral part of the overall assessment of an insecticide's ability to control disease transmission in any given area.
Article
Volatile oils extracted by hydrodistillation from six plant species growing in the Kenyan coast, Croton pseudopulchellus Pax, Mkilua fragrans Verdc. (Annonaceae), Endostemon tereticaulis (poir.) Ashby, Ocimum forskolei Benth., Ocimum fischeri Guerke and Plectranthus longipes Baker (Labiateae), were evaluated for repellency on forearms of human volunteers against Anopheles gambiae sensu stricto. All oils were found to be more repellent (RC50 range = 0.67-9.21 x 10(-5) mg cm(-2)) than DEET (RC50 = 33 x 10(-5) mg cm(-2)). The individual components of the oils were identified by GC-MS and GC co-injections with authentic standards. The repellency of 15 of the main constituents of the different oils (which had not been previously assayed) was evaluated. Although some of these showed relatively high individual repellencies, none was comparable to the parent essential oils. Partial synthetic blends of selected constituents with moderate or relatively high individual repellency against the vector were also assayed. Four of these exhibited activities comparable to or higher than those of the corresponding parent oils, indicating interesting blend effects in the repellent action of the oils against the mosquito. The implication of these results in the utilization of the plants is discussed.
Status of organophosphate and carbamate resistance in Anopheles gambiae sensu lato from the south and north Benin
  • N Aïzoun
  • R Aïkpon
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Aïzoun, N., Aïkpon, R., Gnanguenon, V., Oussou, O., Agossa, F., Padonou, G., Akogbéto, M., 2013. Status of organophosphate and carbamate resistance in Anopheles gambiae sensu lato from the south and north Benin, West Africa. Parasit Vectors. 6, 274. doi: 10.1186/1756-3305-6-274.
Resistance to Selected Pyrethroid Insecticides in the Malaria Mosquito
  • Ali Khan
  • H A Akram
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Ali Khan, H.A., Akram, W., Lee, S., 2018. Resistance to Selected Pyrethroid Insecticides in the Malaria Mosquito, Anopheles stephensi(Diptera: Muscidae), From Punjab, Pakistan. J. Med. Entomol. https://doi.org/10.1093/jme/tjx247.
Insecticide resistance in malaria vectors in Kumasi, Ghana. Parasites Vectors
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Baffour-Awuah, S., Augustina, A.A., Maiga-Ascofare, O., Dieudonné, S.D., Adjei-Kusi, P., Owusu-Dabo, E., Obiri-Danso, K., 2016. Insecticide resistance in malaria vectors in Kumasi, Ghana. Parasites Vectors. 9, 633. doi 10.1186/s13071-016-1923-5
Insecticide resistance toAnopheles spp. mosquitoes (Diptera: Culicidae) in Nigeria: A
  • B R Mohammed
  • Y M Abdulsalam
  • Y Y Deeni
Mohammed, B.R., Abdulsalam, Y.M., Deeni, Y.Y., 2015. Insecticide resistance toAnopheles spp. mosquitoes (Diptera: Culicidae) in Nigeria: A. Int. J. Mosq. Res. 3, 56-63.
Evaluation of extracts and oils of mosquito (Diptera: culicidae) repellent plants from Sweden and Guinea-Bissau
  • Jaenson
Insecticide resistance toAnopheles spp. mosquitoes (Diptera: Culicidae) in Nigeria: A
  • Mohammed