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BACKGROUND: A treated fabric device for emanating the volatile pyrethroid transfluthrin was recently developed in Tanzania that protected against night-biting Anopheles and Culex mosquitoes for several months. Here perceptions of community end users provided with such transfluthrin emanators, primarily intended to protect them against day-active Aedes vectors of human arboviruses that often attack people outdoors, were assessed in Port-au-Prince, Haiti. METHODS: Following the distribution of transfluthrin emanators to participating households in poor-to-middle class urban neighbourhoods, questionnaire surveys and in-depth interviews of end-user households were supplemented with conventional and Photovoice-based focus group discussions. Observations were assessed synthetically to evaluate user perceptions of protection and acceptability, and to solicit advice for improving and promoting them in the future. RESULTS: Many participants viewed emanators positively and several outlined various advantages over current alternatives, although some expressed concerns about smell, health hazards, bulkiness, unattractiveness and future cost. Most participants expressed moderate to high satisfaction with protection against mosquitoes, especially indoors. Protection against other arthropod pests was also commonly reported, although satisfaction levels were highly variable. Diverse use practices were reported, some of which probably targeted nocturnal Culex resting indoors, rather than Aedes attacking them outdoors during daylight hours. Perceived durability of protection varied: While many participants noted some slow loss over months, others noted rapid decline within days. A few participants specifically attributed efficacy loss to outdoor use and exposure to wind or moisture. Many expressed stringent expectations of satisfactory protection levels, with even a single mosquito bite considered unsatisfactory. Some participants considered emanators superior to fans, bedsheets, sprays and coils, but it is concerning that several preferred them to bed nets and consequently stopped using the latter. CONCLUSIONS: The perspectives shared by Haitian end-users are consistent with those from similar studies in Brazil and recent epidemiological evidence from Peru that other transfluthrin emanator products can protect against arbovirus infection. While these encouraging sociological observations contrast starkly with evidence of essentially negligible effects upon Aedes landing rates from parallel entomological assessments across Haiti, Tanzania, Brazil and Peru, no other reason to doubt the generally encouraging views expressed herein by Haitian end users could be identified.
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Ciclopropanos , Fluorbenzenos , Controle de Mosquitos , Haiti , Animais , Humanos , Controle de Mosquitos/métodos , Feminino , Masculino , Inseticidas , Adulto , Mosquitos Vetores , Aedes/efeitos dos fármacos , Pessoa de Meia-Idade , Inquéritos e Questionários , Anopheles/efeitos dos fármacos , Culex/efeitos dos fármacosRESUMO
BACKGROUND: A low technology emanator device for slowly releasing vapour of the volatile pyrethroid transfluthrin was recently developed in Tanzania that provides robust protection against night biting Anopheles and Culex vectors of malaria and filariasis for several months. Here these same emanator devices were assessed in Dar es Salaam city, as a means of protection against outdoor-biting Aedes (Stegomia) aegypti, the most important vector of human arboviruses worldwide, in parallel with similar studies in Haiti and Brazil. METHODS: A series of entomological experiments were conducted under field and semi-field conditions, to evaluate whether transfluthrin emanators protect against wild Ae. aegypti, and also compare the transfluthrin responsiveness of Ae. aegypti originating from wild-caught eggs to established pyrethroid-susceptible Ae. aegypti and Anopheles gambiae colonies. Preliminary measurements of transfluthrin vapour concentration in air samples collected near treated emanators were conducted by gas chromatography-mass spectrometry. RESULTS: Two full field experiments with four different emanator designs and three different transfluthrin formulations consistently indicated negligible reduction of human landing rates by wild Ae. aegypti. Under semi-field conditions in large cages, 50 to 60% reductions of landing rates were observed, regardless of which transfluthrin dose, capture method, emanator placement position, or source of mosquitoes (mildly pyrethroid resistant wild caught Ae. aegypti or pyrethroid-susceptible colonies of Ae. aegypti and An. gambiae) was used. Air samples collected immediately downwind from an emanator treated with the highest transfluthrin dose (15g), contained 12 to 19 µg/m3 transfluthrin vapour. CONCLUSIONS: It appears unlikely that the moderate levels of pyrethroid resistance observed in wild Ae. aegypti can explain the modest-to-undetectable levels of protection exhibited. While potential inhalation exposure could be of concern for the highest (15g) dose evaluated, 3g of transfluthrin appears sufficient to achieve the modest levels of protection that were demonstrated entomologically. While the generally low levels of protection against Aedes reported here from Tanzania, and from similar entomological studies in Haiti and Brazil, are discouraging, complementary social science studies in Haiti and Brazil suggest end-users perceive valuable levels of protection against mosquitoes. It therefore remains unclear whether transfluthrin emanators have potential for protecting against Aedes vectors of important human arboviruses.
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Aedes , Ciclopropanos , Fluorbenzenos , Inseticidas , Controle de Mosquitos , Animais , Tanzânia , Aedes/efeitos dos fármacos , Ciclopropanos/farmacologia , Controle de Mosquitos/métodos , Inseticidas/farmacologia , Mosquitos Vetores/efeitos dos fármacos , Humanos , Anopheles/efeitos dos fármacos , Mordeduras e Picadas de Insetos/prevenção & controle , PiretrinasRESUMO
BACKGROUND: A simple treated fabric device for passively emanating the volatile pyrethroid transfluthrin was recently developed in Tanzania that protected against nocturnal Anopheles and Culex mosquitoes for several months. Here these transfluthrin emanators were assessed in Port-au-Prince, Haiti against outdoor-biting Aedes. METHODS: Transfluthrin emanators were distributed to participating households in poor-to-middle class urban neighbourhoods and evaluated once every two months in terms of their effects on human landing rates of wild Aedes populations. A series of three such entomological assessment experiments were conducted, to examine the influence of changing weather conditions, various transfluthrin formulations and emanator placement on protective efficacy measurements. Laboratory experiments assessed resistance of local Aedes aegypti to transfluthrin and deltamethrin, and the irritancy and repellency of the transfluthrin-treated fabric used in the field. RESULTS: Across all three entomological field assessments, little evidence of protection against wild Ae. aegypti was observed, regardless of weather conditions, transfluthrin formulation or emanator placement: A generalized linear mixed model fitted to the pooled data from all three assessment rounds (921 females caught over 5129 hours) estimated a relative landing rate [95% Confidence interval] of 0.87 [0.73, 1.04] for users of treated versus untreated emanators (P = 0.1241). Wild Ae. aegypti in this setting were clearly resistant to transfluthrin when compared to a fully susceptible colony. CONCLUSIONS: Transfluthrin emanators had little if any apparent effect upon Aedes landing rates by wild Ae. aegypti in urban Haiti, and similar results have been obtained by comparable studies in Tanzania, Brazil and Peru. In stark contrast, however, parallel sociological assessments of perspectives among these same end-users in urban Haitian communities indicate strong satisfaction in terms of perceived protection against mosquitoes. It remains unclear why the results obtained from these complementary entomological and sociological assessments in Haiti differ so much, as do those from a similar set of studies in Brazil. It is encouraging, however, that similar contrasts between the entomological and epidemiological results of a recent large-scale assessment of another transfluthrin emanator product in Peru, which indicate they provide useful protection against Aedes-borne arboviral infections, despite apparently providing only modest protection against Aedes mosquito bites.
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Aedes , Ciclopropanos , Fluorbenzenos , Inseticidas , Controle de Mosquitos , Animais , Aedes/efeitos dos fármacos , Ciclopropanos/farmacologia , Haiti , Controle de Mosquitos/métodos , Humanos , Inseticidas/farmacologia , Feminino , Piretrinas/farmacologia , Mosquitos Vetores/efeitos dos fármacos , Resistência a Inseticidas , Mordeduras e Picadas de Insetos/prevenção & controle , Nitrilas/farmacologia , Características da Família , Repelentes de Insetos/farmacologiaRESUMO
Insecticide resistance in mosquitoes is spreading worldwide and represents a growing threat to vector control. Insecticide resistance is caused by different mechanisms including higher metabolic detoxication, target-site modification, reduced penetration and behavioral changes that are not easily detectable with simple diagnostic methods. Indeed, most molecular resistance diagnostic tools are costly and labor intensive and then difficult to use for routine monitoring of insecticide resistance. The present study aims to determine whether mosquito susceptibility status against the pyrethroid insecticides (mostly used for mosquito control) could be established by the protein signatures of legs and/or thoraxes submitted to MALDI-TOF Mass Spectrometry (MS). The quality of MS spectra for both body parts was controlled to avoid any bias due to unconformity protein profiling. The comparison of MS profiles from three inbreeds Ae. aegypti lines from French Guiana (IRF, IR03, IR13), with distinct deltamethrin resistance genotype / phenotype and the susceptible reference laboratory line BORA (French Polynesia), showed different protein signatures. On both body parts, the analysis of whole protein profiles revealed a singularity of BORA line compared to the three inbreeding lines from French Guiana origin, suggesting that the first criteria of differentiation is the geographical origin and/or the breeding history rather than the insecticide susceptibility profile. However, a deeper analysis of the protein profiles allowed to identify 10 and 11 discriminating peaks from leg and thorax spectra, respectively. Among them, a specific peak around 4870 Da was detected in legs and thoraxes of pyrethroid resistant lines compared to the susceptible counterparts hence suggesting that MS profiling may be promising to rapidly distinguish resistant and susceptible phenotypes. Further work is needed to confirm the nature of this peak as a deltamethrin resistant marker and to validate the routine use of MS profiling to track insecticide resistance in Ae. aegypti field populations.
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Aedes , Resistência a Inseticidas , Inseticidas , Nitrilas , Piretrinas , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por Matriz , Animais , Piretrinas/farmacologia , Aedes/efeitos dos fármacos , Aedes/genética , Aedes/metabolismo , Resistência a Inseticidas/genética , Nitrilas/farmacologia , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por Matriz/métodos , Inseticidas/farmacologia , Mosquitos Vetores/efeitos dos fármacos , Mosquitos Vetores/genética , Dengue/virologia , Proteínas de Insetos/genética , Proteínas de Insetos/metabolismo , FemininoRESUMO
The development of insecticide resistance in mosquitoes of public health importance has encouraged extensive research into innovative vector control methods. Terpenes are the largest among Plants Secondary Metabolites and have been increasingly studied for their potential as insecticidal control agents. Although promising, terpenes are insoluble in water, and they show low residual life which limits their application for vector control. In this study, we developed and evaluated the performances of terpenoid-based nanoemulsions (TNEs) containing myrcene and p-cymene against the dengue vector Aedes aegypti and investigated their potential toxicity against non-target organisms. Our results showed that myrcene and p-cymene showed moderate larvicidal activity against mosquito larvae compared to temephos an organophosphate widely used for mosquito control. However, we showed similar efficacy of TNEs against both susceptible and highly insecticide-resistant mosquitoes from French Guyana, hence suggesting an absence of cross-resistance with conventional insecticides. We also showed that TNEs remained effective for up to 45 days in laboratory conditions. The exposure of zebrafish to TNEs triggered behavioral changes in the fish at high doses but they did not alter the normal functioning of zebrafish organs, suggesting a good tolerability of non-target organisms to these molecules. Overall, this study provides new insights into the insecticidal properties and toxicity of terpenes and terpenoid-based formulations and confirms that TNE may offer interesting prospects for mosquito control as part of integrated vector management.
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Monoterpenos Acíclicos , Aedes , Alcenos , Cimenos , Dengue , Inseticidas , Animais , Terpenos/farmacologia , Peixe-Zebra , Mosquitos Vetores , Inseticidas/farmacologia , Dengue/prevenção & controle , LarvaRESUMO
Plant-based insecticides offer advantages such as negligible residual effects, reduced risks to both humans and the environment, and immunity to resistance issues that plague conventional chemicals. However, the practical use of monoterpenes in insect control has been hampered by challenges including their poor solubility and stability in aqueous environments. In recent years, the application of nanotechnology-based formulations, specifically nanoemulsions, has emerged as a prospective strategy to surmount these obstacles. In this study, we developed and characterized nanoemulsions based on cymene and myrcene and assessed their toxicity both in vitro using human keratinocytes (HaCAT) cells and in an in vivo model involving Galleria mellonella larvae. Additionally, we investigated the insecticidal efficacy of monoterpenes against the mosquito Aedes aegypti, the primary dengue vector, via larval bioassay. Employing a low-energy approach, we successfully generated nanoemulsions. The cymene-based nanoemulsion exhibited a hydrodynamic diameter of approximately 98 nm and a zeta potential of -25 mV. The myrcene-based nanoemulsion displayed a hydrodynamic diameter of 118 nm and a zeta potential of -20 mV. Notably, both nanoemulsions demonstrated stability over 60 days, accompanied by controlled release properties and low toxicity towards HaCAT cells and Galleria mellonella larvae. Moreover, the nanoemulsions exhibited significant lethality against third-instar Aedes aegypti larvae at a concentration of 50 mg/L. In conclusion, the utilization of nanoemulsions encapsulating cymene and myrcene presents a promising avenue for overcoming the limitations associated with poor solubility and stability of monoterpenes. This study sheds light on the potential of the nanoemulsions as effective and environmentally friendly insecticides in the ongoing battle against mosquito-borne diseases.
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Insecticide resistance in Aedes aegypti poses a significant threat to disease control. One form of resistance, caused by kdr mutations in the NaV gene, hinders vector control efforts in Brazil. Despite genetic differences typically accumulating among isolated populations, this mosquito can actively and passively disperse through human transportation. Our study investigated the genetic structure and spread of kdr mutations in Ae. aegypti populations across six localities in Amapá State, Brazil, within the Amazonian Forest. Using 12 microsatellite loci and qPCR methods, we assessed genetic structure and identified three common kdr mutations (V410L, V1016I, and F1534C). High prevalence of kdr alleles was observed in all localities, indicating widespread distribution in Amapá State. Microsatellite analysis revealed differentiation among mosquito populations, dividing them into two distinct clusters supported by Bayesian and DAPC analyses. Oiapoque, located along the northern border with French Guiana, exhibited the highest kdr frequencies and genetic differentiation compared to other localities. Our findings suggest genetic structure in Ae. aegypti populations in Amapá State, with some passive gene flow between clusters. The study underscores the need for continuous surveillance of Ae. aegypti populations to monitor the spread of insecticide resistance and inform effective vector control strategies.
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Aedes , Inseticidas , Piretrinas , Animais , Humanos , Aedes/genética , Brasil , Teorema de Bayes , Mutação , Alelos , Resistência a Inseticidas/genética , Inseticidas/farmacologiaRESUMO
Mosquito-borne diseases such as malaria, dengue, or chikungunya have been re-emerging all over the world, including in Europe. Managing resistance to public health pesticides in mosquitoes is essential and requires global, integrated, and coordinated actions and strong engagement of decision-makers, scientists, and public health operators. In this context, the present work aims at proposing an integrated plan of resistance surveillance in France and in the French Overseas territories in order to provide graduated and appropriate responses according to the situation. Briefly, the plan relies on periodic monitoring of insecticide resistance at the population level in predefined sites using adequate biological, molecular, and/or biochemical approaches and a stratification of the level of resistance risk at the scale of territory to adjust surveillance and vector control actions. The plan relies on the latest methods and indicators used for resistance monitoring as recommended by the World Health Organization in order to prevent or slow down its extension in space and time. The plan has been developed for France but can be easily adapted to other countries in order to provide a coordinated response to the growing problem of mosquito resistance in Europe.
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BACKGROUND: The continued spread of insecticide resistance in mosquito vectors of malaria and arboviral diseases may lead to operational failure of insecticide-based interventions if resistance is not monitored and managed efficiently. This study aimed to develop and validate a new WHO glass bottle bioassay method as an alternative to the WHO standard insecticide tube test to monitor mosquito susceptibility to new public health insecticides with particular modes of action, physical properties or both. METHODS: A multi-centre study involving 21 laboratories worldwide generated data on the susceptibility of seven mosquito species (Aedes aegypti, Aedes albopictus, Anopheles gambiae sensu stricto [An. gambiae s.s.], Anopheles funestus, Anopheles stephensi, Anopheles minimus and Anopheles albimanus) to seven public health insecticides in five classes, including pyrethroids (metofluthrin, prallethrin and transfluthrin), neonicotinoids (clothianidin), pyrroles (chlorfenapyr), juvenile hormone mimics (pyriproxyfen) and butenolides (flupyradifurone), in glass bottle assays. The data were analysed using a Bayesian binomial model to determine the concentration-response curves for each insecticide-species combination and to assess the within-bioassay variability in the susceptibility endpoints, namely the concentration that kills 50% and 99% of the test population (LC50 and LC99, respectively) and the concentration that inhibits oviposition of the test population by 50% and 99% (OI50 and OI99), to measure mortality and the sterilizing effect, respectively. RESULTS: Overall, about 200,000 mosquitoes were tested with the new bottle bioassay, and LC50/LC99 or OI50/OI99 values were determined for all insecticides. Variation was seen between laboratories in estimates for some mosquito species-insecticide combinations, while other test results were consistent. The variation was generally greater with transfluthrin and flupyradifurone than with the other compounds tested, especially against Anopheles species. Overall, the mean within-bioassay variability in mortality and oviposition inhibition were < 10% for most mosquito species-insecticide combinations. CONCLUSION: Our findings, based on the largest susceptibility dataset ever produced on mosquitoes, showed that the new WHO bottle bioassay is adequate for evaluating mosquito susceptibility to new and promising public health insecticides currently deployed for vector control. The datasets presented in this study have been used recently by the WHO to establish 17 new insecticide discriminating concentrations (DCs) for either Aedes spp. or Anopheles spp. The bottle bioassay and DCs can now be widely used to monitor baseline insecticide susceptibility of wild populations of vectors of malaria and Aedes-borne diseases worldwide.
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Anopheles , Inseticidas , Malária , Piretrinas , Animais , Feminino , Inseticidas/farmacologia , Mosquitos Vetores , Saúde Pública , Teorema de Bayes , Controle de Mosquitos/métodos , Piretrinas/farmacologia , Resistência a Inseticidas , Bioensaio , Organização Mundial da SaúdeRESUMO
BACKGROUND: Despite a global decrease in malaria burden worldwide, malaria remains a major public health concern, especially in Benin children, the most vulnerable group. A better understanding of malaria's spatial and age-dependent characteristics can help provide durable disease control and elimination. This study aimed to analyze the spatial distribution of Plasmodium falciparum malaria infection and disease among children under five years of age in Benin, West Africa. METHODS: A cross-sectional epidemiological and clinical survey was conducted using parasitological examination and rapid diagnostic tests (RDT) in Benin. Interviews were done with 10,367 children from 72 villages across two health districts in Benin. The prevalence of infection and clinical cases was estimated according to age. A Bayesian spatial binomial model was used to estimate the prevalence of malaria infection, and clinical cases were adjusted for environmental and demographic covariates. It was implemented in R using Integrated Nested Laplace Approximations (INLA) and Stochastic Partial Differentiation Equations (SPDE) techniques. RESULTS: The prevalence of P. falciparum infection was moderate in the south (34.6%) of Benin and high in the northern region (77.5%). In the south, the prevalence of P. falciparum infection and clinical malaria cases were similar according to age. In northern Benin children under six months of age were less frequently infected than children aged 6-11, 12-23, 24-60 months, (p < 0.0001) and had the lowest risk of malaria cases compared to the other age groups (6-12), (13-23) and (24-60): OR = 3.66 [2.21-6.05], OR = 3.66 [2.21-6.04], and OR = 2.83 [1.77-4.54] respectively (p < 0.0001). Spatial model prediction showed more heterogeneity in the south than in the north but a higher risk of malaria infection and clinical cases in the north than in the south. CONCLUSION: Integrated and periodic risk mapping of Plasmodium falciparum infection and clinical cases will make interventions more evidence-based by showing progress or a lack in malaria control.
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Malária Falciparum , Malária , África Ocidental , Teorema de Bayes , Benin/epidemiologia , Criança , Pré-Escolar , Estudos Transversais , Fácies , Humanos , Malária/epidemiologia , Malária Falciparum/diagnóstico , Malária Falciparum/epidemiologiaAssuntos
Malária , Controle de Mosquitos , Humanos , Malária/prevenção & controle , Malária/transmissãoRESUMO
[This corrects the article DOI: 10.1371/journal.pntd.0006845.].
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Humoral immunity to Plasmodium falciparum is acquired after repeated infections, and can lead to clinical protection. This study aimed to evaluate how human-, parasite-, and environment-related determinants can modulate the dynamics of IgG responses to Plasmodium falciparum after an infection. Individuals (n = 68, average age = 8.2 years) with uncomplicated malaria were treated with ACT and followed up for 42 days. IgG responses to P. falciparum merozoite antigens (PfMSP1, PfMSP3, PfAMA1, PfGLURP-R0), to whole schizont extract (PfSchz), and to Anopheles gSG6-P1 and Aedes Nterm-34 kDa salivary peptides were measured. Regression analyses were used to identify factors that influence the dynamics of IgG response to P. falciparum antigen between D0 and D42, including demographic and biological factors and the level of exposure to mosquito bites. The dynamics of IgG response to P. falciparum differed according to the antigen. According to multivariate analysis, IgG responses to PfSchz and to PfGLURP-R0 appear to be affected by exposure to Aedes saliva and are associated with age, parasite density, and anti-Plasmodium pre-existing immune response at study inclusion. The present work shows that human exposure to Aedes saliva may contribute, in addition to other factors, to the regulation of anti-Plasmodium immune responses during a natural infection.
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BACKGROUND: Aedes mosquitoes are vectors for several major arboviruses of public health concern including dengue viruses. The relationships between Aedes infestation and disease transmission are complex wherein the epidemiological dynamics can be difficult to discern because of a lack of robust and sensitive indicators for predicting transmission risk. This study investigates the use of anti-Aedes saliva antibodies as a serological biomarker for Aedes mosquito bites to assess small scale variations in adult Aedes density and dengue virus (DENV) transmission risk in northeastern Thailand. Individual characteristics, behaviors/occupation and socio-demographics, climatic and epidemiological risk factors associated with human-mosquito exposure are also addressed. METHODS: The study was conducted within a randomized clustered control trial in Roi Et and Khon Kaen provinces over a consecutive 19 months period. Thirty-six (36) clusters were selected, each of ten houses. Serological and entomological surveys were conducted in all houses every four months and monthly in three sentinel households per cluster between September 2017 and April 2019 for blood spot collections and recording concurrent immature and adult Aedes indices. Additionally, the human exposure to Aedes mosquito bites (i.e., Mosquito Exposure Index or MEI) was estimated by ELISA measuring levels of human antibody response to the specific Nterm-34 kDa salivary antigen. The relationships between the MEI, vector infestation indices (adult and immature stages) and vector DENV infection were evaluated using a two-level (house and individual levels) mixed model analysis with one-month lag autoregressive correlation. RESULTS: There was a strong positive relationship between the MEI and adult Aedes (indoor and outdoor) density. Individuals from households with a medium mosquito density (mean difference: 0.091, p<0.001) and households with a high mosquito density (mean difference: 0.131, p<0.001) had higher MEI's compared to individuals from households without Aedes. On a similar trend, individuals from households with a low, medium or high indoor Aedes densities (mean difference: 0.021, p<0.007, 0.053, p<0.0001 and 0.037, p<0.0001 for low, medium and high levels of infestation, respectively) had higher MEI than individuals from houses without indoor Aedes. The MEI was driven by individual characteristics, such as gender, age and occupation/behaviors, and varied according to climatic, seasonal factors and vector control intervention (p<0.05). Nevertheless, the study did not demonstrate a clear correlation between MEI and the presence of DENV-infected Aedes. CONCLUSION: This study represents an important step toward the validation of the specific IgG response to the Aedes salivary peptide Nterm-34kDa as a proxy measure for Aedes infestation levels and human-mosquito exposure risk in a dengue endemic setting. The use of the IgG response to the Nterm-34 kDa peptide as a viable diagnostic tool for estimating dengue transmission requires further investigations and validation in other geographical and transmission settings.
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Aedes/fisiologia , Aedes/virologia , Mordeduras e Picadas de Insetos/epidemiologia , Aedes/crescimento & desenvolvimento , Animais , Biomarcadores/sangue , Dengue/epidemiologia , Dengue/transmissão , Vírus da Dengue/isolamento & purificação , Ensaio de Imunoadsorção Enzimática , Feminino , Humanos , Imunoglobulina G/análise , Mordeduras e Picadas de Insetos/imunologia , Masculino , Mosquitos Vetores/virologia , Saliva/imunologia , Tailândia/epidemiologiaRESUMO
Aedes albopictus and Aedes aegypti are invasive mosquito species that impose a substantial risk to human health. To control the abundance and spread of these arboviral pathogen vectors, the sterile insect technique (SIT) is emerging as a powerful complement to most commonly-used approaches, in part, because this technique is ecologically benign, specific, and non-persistent in the environment if releases are stopped. Because SIT and other similar vector control strategies are becoming of increasing interest to many countries, we offer here a pragmatic and accessible 'roadmap' for the pre-pilot and pilot phases to guide any interested party. This will support stakeholders, non-specialist scientists, implementers, and decision-makers. Applying these concepts will ensure, given adequate resources, a sound basis for local field trialing and for developing experience with the technique in readiness for potential operational deployment. This synthesis is based on the available literature, in addition to the experience and current knowledge of the expert contributing authors in this field. We describe a typical path to successful pilot testing, with the four concurrent development streams of Laboratory, Field, Stakeholder Relations, and the Business and Compliance Case. We provide a graphic framework with criteria that must be met in order to proceed.
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[This corrects the article DOI: 10.1371/journal.pntd.0005625.].
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BACKGROUND: In Laos, the malaria burden remains high despite a significant reduction of cases during the last decade. In the context of the disease elimination by 2030, a nationwide entomological survey was conducted to better understand the distribution, abundance and behaviour of major malaria vectors (Anopheles spp.) in the country. METHODS: Mosquito collections were implemented in ten villages from ten provinces during the rainy and dry seasons of 2014 and 2015 by using human landing catch (HLC) and cow bait collection (CBC) methods. After morphological identification in the field, molecular identification of the sibling species of Anopheles mosquitoes from the Funestus, Leucosphyrus, and Maculatus groups were determined using PCR specific alleles. A screening of Plasmodium falciparum and Plasmodium vivax infections in the vectors was carried out by quantitative PCR assays. RESULTS: A total of 14,146 adult mosquitoes representing 25 different Anopheles species were collected and morphologically identified. Molecular identification revealed the presence of 12 sibling species within the main primary vector groups, including Anopheles maculatus, Anopheles rampae, Anopheles sawadwongporni, Anopheles pseudowillmori, Anopheles dravidicus, Anopheles minimus, Anopheles aconitus, Anopheles pampanai, Anopheles harrisoni, Anopheles dirus, Anopheles baimaii, Anopheles nemophilous. Anopheles maculatus and An. minimus were predominant during both the dry and rainy seasons, but showed highly zoophilic preferences (Zoophilic index of 98% and 95%, respectively). Overall, 22% of the total malaria vectors were collected between 10:00 PM and 5:00 AM indoors when people are sleeping. Twenty-seven percent of primary and secondary vectors were collected outdoors before 10:00 PM or after 5:00 AM, times when people are usually awake and outdoors. Only two specimens were positive for P. falciparum, one An. aconitus from Phongsaly and one An. minimus from Vientiane Province CONCLUSIONS: The results indicate that people living in rural areas in Laos are constantly exposed to malaria vectors throughout the year and specifically outdoors. The use of LLINs/IRS remains important but innovative tools and new strategies are needed to address locally, the early and outdoor malaria transmission. Lack of expertise in general entomological methods may further exacerbate the situation.
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Distribuição Animal , Anopheles/fisiologia , Características de História de Vida , Mosquitos Vetores/fisiologia , Plasmodium falciparum/isolamento & purificação , Plasmodium vivax/isolamento & purificação , Animais , Anopheles/classificação , Comportamento Alimentar , Feminino , Laos , Mosquitos Vetores/classificação , Dinâmica PopulacionalRESUMO
BACKGROUND/OBJECTIVES: Dengue fever is an important public health concern in most tropical and subtropical countries, and its prevention and control rest on vector surveillance and control. However, many aspects of dengue epidemiology remain unclear; in particular, the relationship between Aedes vector abundance and dengue transmission risk. This study aims to identify entomological and immunological indices capable of discriminating between dengue case and control (non-case) houses, based on the assessment of candidate indices, as well as individual and household characteristics, as potential risk factors for acquiring dengue infection. METHODS: This prospective, hospital-based, case-control study was conducted in northeastern Thailand between June 2016 and August 2019. Immature and adult stage Aedes were collected at the houses of case and control patients, recruited from district hospitals, and at patients' neighboring houses. Blood samples were tested by RDT and PCR to detect dengue cases, and were processed with the Nterm-34 kDa salivary peptide to measure the human immune response to Aedes bites. Socioeconomic status, and other individual and household characteristics were analyzed as potential risk factors for dengue. RESULTS: Study findings showed complex relationships between entomological indices and dengue risk. The presence of DENV-infected Aedes at the patient house was associated with 4.2-fold higher odds of dengue. On the other hand, Aedes presence (irrespective of infectious status) in the patient's house was negatively associated with dengue. In addition, the human immune response to Aedes bites, was higher in control than in case patients and Aedes adult abundance and immature indices were higher in control than in case houses at the household and the neighboring level. Multivariable analysis showed that children aged 10-14 years old and those aged 15-25 years old had respectively 4.5-fold and 2.9-fold higher odds of dengue infection than those older than 25 years. CONCLUSION: DENV infection in female Aedes at the house level was positively associated with dengue infection, while adult Aedes presence in the household was negatively associated. This study highlights the potential benefit of monitoring dengue viruses in Aedes vectors. Our findings suggest that monitoring the presence of DENV-infected Aedes mosquitoes could be a better indicator of dengue risk than the traditional immature entomological indices.
Assuntos
Aedes , Dengue/transmissão , Mosquitos Vetores/virologia , Adolescente , Adulto , Animais , Estudos de Casos e Controles , Criança , Dengue/epidemiologia , Dengue/virologia , Características da Família , Feminino , Humanos , Masculino , Fatores de Risco , Tailândia/epidemiologia , Adulto JovemRESUMO
BACKGROUND: Members of the Anopheles hyrcanus group have been incriminated as important malaria vectors. This study aims to identify the species and explore the insecticide susceptibility profile within the Anopheles hyrcanus group in Ubon Ratchathani Province, northeastern Thailand where increasing numbers of malaria cases were reported in 2014. METHODS: Between 2013 and 2015, five rounds of mosquito collections were conducted using human landing and cattle bait techniques during both the rainy and dry seasons. Anopheles mosquitoes were morphologically identified and their insecticide susceptibility status was investigated. Synergist bioassays were carried out with An. hyrcanus (s.l.) due to their resistance to all insecticides. An ITS2-PCR assay was conducted to identify to species the Hyrcanus group specimens. RESULTS: Out of 10,361 Anopheles females collected, representing 18 taxa in 2 subgenera, 71.8% were morphologically identified as belonging to the Hyrcanus Group (subgenus Anopheles), followed by An. barbirostris group (7.9%), An. nivipes (6.5%), An. philippinensis (5.9%) and the other 14 Anopheles species. Specimens of the Hyrcanus Group were more prevalent during the rainy season and were found to be highly zoophilic. Anopheles hyrcanus (s.l.) was active throughout the night, with an early peak of activity between 18:00 h and 21:00 h. ITS2-PCR assay conducted on 603 DNA samples from specimens within the Hyrcanus Group showed the presence of five sisters species. Anopheles peditaeniatus was the most abundant species (90.5%, n = 546), followed by An. nitidus (4.5%, n = 27), An. nigerrimus (4.3%, n = 26), An. argyropus (0.5%, n = 3), and An. sinensis (0.2%, n = 1). All An. hyrcanus (s.l.) specimens that were found resistant to insecticides (deltamethrin 0.05%, permethrin 0.75% and DDT 4% and synergist tests) belonged to An. peditaeniatus. The degree of resistance in An. peditaeniatus to each of these three insecticides was approximately 50%. Addition of PBO (Piperonyl butoxide), but not DEF (S.S.S-tributyl phosphotritioate), seemed to restore susceptibility, indicating a potential role of oxidases as a detoxifying enzyme resistance mechanism. CONCLUSIONS: A better understanding of mosquito diversity related to host preference, biting activity and insecticide resistance status will facilitate the implementation of locally adapted vector control strategies.
Assuntos
Anopheles/genética , Resistência a Inseticidas , Inseticidas/farmacologia , Malária/epidemiologia , Controle de Mosquitos , Mosquitos Vetores/genética , Animais , Anopheles/efeitos dos fármacos , Biodiversidade , Feminino , Humanos , Malária/parasitologia , Malária/transmissão , Tailândia/epidemiologiaRESUMO
Cancer is a major public health issue and represents a significant burden in countries with different levels of economic wealth. In parallel, mosquito-borne infectious diseases represent a growing problem causing significant morbidity and mortality worldwide. Acknowledging that these two concerns are both globally distributed, it is essential to investigate whether they have a reciprocal connection that can fuel their respective burdens. Unfortunately, very few studies have examined the link between these two threats. This review provides an overview of the possible links between mosquitoes, mosquito-borne infectious diseases and cancer. We first focus on the impact of mosquitoes on carcinogenesis in humans including the transmission of oncogenic pathogens through mosquitoes, the immune reactions following mosquito bites, the presence of non-oncogenic mosquito-borne pathogens, and the direct transmission of cancer cells. The second part of this review deals with the direct or indirect consequences of cancer in humans on mosquito behaviour. Thirdly, we discuss the potential impacts that natural cancers in mosquitoes can have on their life history traits and therefore on their vector capacity. Finally, we discuss the most promising research avenues on this topic and the integrative public health strategies that could be envisioned in this context.