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2.
Rev Environ Contam Toxicol ; 252: 131-171, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31463624

RESUMO

Anurans from the genus Xenopus have long been used as standard testing organisms and occur naturally in tropical and sub-tropical areas where malaria vector control pesticides are actively used. However, literature on the toxic effects of these pesticides is limited. This review analyses the available data pertaining to both Xenopus and the pesticides used for malaria vector control in order to determine the pesticides that have the greatest potential to influence amphibian health while also identifying gaps in literature that need to be addressed. Amphibian diversity has shown the fastest decline of any group, yet there are still voids in our understanding of how this is happening. The lack of basic toxicity data on amphibians with regard to pesticides is an issue that needs to be addressed in order to improve effectiveness of amphibian conservation strategies. Meta-analyses performed in this review show that, at current usage, with the available acute toxicity literature, the pyrethroid pesticide group could hold the highest potential to cause acute toxicity to Xenopus sp. in relation to the other MVCPs discussed, but the lack of data cripples the efficacy with which meta-analyses can be performed and conclusions made from such analyses. Several studies have shown that DDT accumulates in Xenopus sp. from malaria vector control areas, but accumulation of other MVCPs in frogs is still largely unknown. Through this review we hope to encourage future research into the field of amphibian ecotoxicology and to promote the use of the Xenopus standard model in order to build comprehensive datasets that may be used in amphibian conservation.


Assuntos
Ecotoxicologia , Poluentes Ambientais/toxicidade , Malária , Controle de Mosquitos , Mosquitos Vetores , Praguicidas/toxicidade , Animais , Anopheles , Xenopus , Xenopus laevis
3.
Acta Trop ; 201: 105204, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31574253

RESUMO

Gut microbiota communities in mosquitoes are influenced among others, by developmental stage. There is evidence that the aquatic environment where larvae feed influences the mosquito gut bacterial community composition with only a subgroup of these bacteria been transmitted trans-stadially to adults. This study evaluated the gut bacterial composition of Anopheles albimanus larvae, emerged and circulating mosquitoes, as well as water from the larval habitat, to elucidate transitions in these bacterial communities and determine the final composition in circulating mosquitoes. A 16S rRNA Illumina sequencing allowed to determine that Proteobacteria was the most abundant phylum in larvae (72.4%), emerged mosquitoes (75%), circulating adults (45.4%) and water from the larval habitat (79.1%). A core microbiome analysis evidenced that Enterobacter, Bacillus and Staphylococcus genera were the core bacterial microbiota (OTUs detected in >90%) in the four groups evaluated. PCoA cluster based on Jaccard and Bray Curtis distances showed two main bacterial clusters, one comprising the emerged and circulating adults, and the other the larvae. The results indicated that the gut microbiota of An. albimanus larvae is composed of bacteria acquired from the larval habitat; then, a rearrangement of the bacterial communities occurs in the trans-stadial passage. However, the higher bacterial richness detected in circulating adults suggests bacterial acquisition from the terrestrial environment where the mosquito feeds. Finally, the trans-stadially passage of some bacteria makes of interest their evaluation as candidates for paratransgenic control.


Assuntos
Anopheles/genética , Anopheles/microbiologia , Microbioma Gastrointestinal/genética , Larva/genética , Larva/microbiologia , Pupa/microbiologia , Fatores Etários , Animais , Colômbia , Pupa/genética
4.
Rev Soc Bras Med Trop ; 52: e20190308, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31800921

RESUMO

Malaria, a mosquito-borne infectious disease, is considered a significant global health burden. Climate changes or different weather conditions may impact infectious diseases, specifically those transmitted by insect vectors and contaminated water. Based on the current predictions for climate change associated with the increase in carbon dioxide concentrations in the atmosphere and the increase in atmospheric temperature, the Intergovernmental Panel on Climate Change predicts that in 2050, malaria may threaten some previously unexposed areas worldwide and cause a 50% higher probability of malaria cases. Climate-based distribution models of malaria depict an increase in the geographic distribution of the disease as global environmental temperatures and conditions worsen. Researchers have studied the influence of changes in climate on the prevalence of malaria using different mathematical models that consider different variables and predict the conditions for malaria distribution. In this context, we conducted a mini-review to elucidate the important aspects described in the literature on the influence of climate change in the distribution and transmission of malaria. It is important to develop possible risk management strategies and enhance the surveillance system enhanced even in currently malaria-free areas predicted to experience malaria in the future.


Assuntos
Anopheles/parasitologia , Mudança Climática , Malária/transmissão , Mosquitos Vetores/parasitologia , Animais , Modelos Biológicos , Dinâmica Populacional
5.
Parasit Vectors ; 12(1): 522, 2019 Nov 05.
Artigo em Inglês | MEDLINE | ID: mdl-31690332

RESUMO

BACKGROUND: Insecticides formulated into products that target Anopheles mosquitos have had an immense impact on reducing malaria cases in Africa. However, resistance to currently used insecticides is spreading rapidly and there is an urgent need for alternative public health insecticides. Potential new insecticides must be screened against a range of characterized mosquito strains to identify potential resistance liabilities. The Liverpool School of Tropical Medicine maintains three susceptible and four resistant Anopheles strains that are widely used for screening for new insecticides. The properties of these strains are described in this paper. METHODS: WHO tube susceptibility bioassays were used for colony selection and to screen for resistance to the major classes of public health insecticides. Topical and tarsal contact bioassays were used to produce dose response curves to assess resistance intensity. Bioassays with the synergist piperonyl butoxide were also performed. Taqman™ assays were used to screen for known target site resistance alleles (kdr and ace-1). RT-qPCR was used to quantify expression of genes associated with pyrethroid resistance. RESULTS: Pyrethroid selection pressure has maintained resistance to this class in all four resistant strains. Some carbamate and organophosphate resistance has been lost through lack of exposure to these insecticide classes. The Anopheles gambiae (sensu lato) strains, VK7 2014, Banfora M and Tiassalé 13 have higher levels of pyrethroid resistance than the An. funestus FUMOZ-R strain. Elevated expression of P450s is found in all four strains and the 1014F kdr mutation is present in all three An. gambiae strains at varying frequencies. Tarsal contact data and overexpression of CYP4G16 and SAP2 suggest penetration barriers and/or sequestration also confer resistance in Banfora M. CONCLUSIONS: Continual selection with deltamethrin has maintained a stable pyrethroid-resistant phenotype over many generations. In conjunction with a standardized rearing regime, this ensures quality control of strains over time allowing for robust product comparison and selection of optimal products for further development. The identification of multiple mechanisms underpinning insecticide resistance highlights the importance of screening new compounds against a range of mosquito strains.


Assuntos
Anopheles/classificação , Inseticidas , Malária/prevenção & controle , Controle de Mosquitos/métodos , Mosquitos Vetores/classificação , Análise de Variância , Animais , Anopheles/genética , Bioensaio , Sistema Enzimático do Citocromo P-450/análise , Sistema Enzimático do Citocromo P-450/genética , DNA/genética , DNA/isolamento & purificação , Relação Dose-Resposta a Droga , Feminino , Técnicas de Genotipagem , Resistência a Inseticidas , Malária/transmissão , Controle de Mosquitos/normas , Mosquitos Vetores/genética , Mutação Puntual , Piretrinas
6.
BMC Public Health ; 19(1): 1456, 2019 Nov 06.
Artigo em Inglês | MEDLINE | ID: mdl-31694595

RESUMO

BACKGROUND: Pesticides remain the mainstay for the control of agricultural pests and disease vectors. However, their indiscriminate use in agriculture has led to development of resistance to both crop pests and disease vectors. This threatens to undermine the success gained through the implementation of chemical based vector control programs. We investigated the practices of farmers with regard to pesticide usage in the vegetable growing areas and their impact on susceptibility status of An. gambiae s.l. METHODS: A stratified multistage sampling technique using the administrative structure of the Tanzanian districts as sampling frame was used. Wards, villages and then participants with farms where pesticides are applied were purposively recruited at different stages of the process, 100 participants were enrolled in the study. The same villages were used for mosquito larvae sampling from the farms and the surveys were complimented by the entomological study. Larvae were reared in the insectary and the emerging 2-3 days old female adults of Anopheles gambiae s.l were subjected to susceptibility test. RESULTS: Forty eight pesticides of different formulations were used for control of crop and Livestock pests. Pyrethroids were the mostly used class of pesticides (50%) while organophosphates and carbamates were of secondary importance. Over 80% of all farmers applied pesticides in mixed form. Susceptibility test results confirmed high phenotypic resistance among An. gambiae populations against DDT and the pyrethroids (Permethrin-0.75%, Cyfluthrin-0.15%, Deltametrin-0.05% and Lambdacyhalothrin-0.05%) with mortality rates 54, 61, 76 and 71%, respectively. Molecular analysis showed An. arabiensis as a dominant species (86%) while An. gambiae s.s constituted only 6%. The kdr genes were not detected in all of the specimens that survived insecticide exposures. CONCLUSION: The study found out that there is a common use of pyrethroids in farms, Livestocks as well as in public health. The study also reports high phenotypic resistance among An. gambiae s.l against most of the pyrethroids tested. The preponderance of pyrethroids in agriculture is of public health concern because this is the class of insecticides widely used in vector control programs and this calls for combined integrated pest and vector management (IPVM).


Assuntos
Agricultura/estatística & dados numéricos , Doenças Endêmicas/prevenção & controle , Resistência a Inseticidas , Inseticidas/farmacologia , Malária/prevenção & controle , Mosquitos Vetores/efeitos dos fármacos , Animais , Anopheles/efeitos dos fármacos , Fazendeiros/estatística & dados numéricos , Humanos , Larva/efeitos dos fármacos , Malária/epidemiologia , Tanzânia/epidemiologia
7.
Zootaxa ; 4565(2): zootaxa.4565.2.7, 2019 Mar 08.
Artigo em Inglês | MEDLINE | ID: mdl-31716480

RESUMO

The Nuneztovari Complex of Anopheles (Diptera: Culicidae) comprises four species: An. nuneztovari Gabaldon, An. goeldii Rozeboom Gabaldon, An. dunhami Causey and An. nuneztovari species A. This study aimed to identify morphologically the species of the Nuneztovari Complex that occur in the area of the Belo Monte hydroelectric dam. The morphological identification of adult males and male genitalia (aedeagus and ventral claspette) was performed. A statistical analysis of the difference in aedeagal leaflet length was done using the Mann-Whitney test. Of the 38 male genitalia of specimens of the Nuneztovari Complex examined, 33 were identified as An. goeldii/An. nuneztovari A and five as An. nuneztovari s.s. A statistically significant difference in aedeagal leaflet length was detected between the species: the mean length was 1.23 µm for An. goeldii/An. nuneztovari A and 9.18 µm for An. nuneztovari s.s. This is the first record of An. nuneztovari s.s.in areas of environmental modification in the Brazilian Amazon. This study provides a measurement tool that can identify and differentiate species of the complex in the region, which can be applied to the other species of the complex as well to other anopheline species; thus, fostering the acquisition of information about the role of each species in malaria transmission.


Assuntos
Anopheles , Malária , Animais , Brasil , Genitália Masculina , Masculino
8.
Zhongguo Xue Xi Chong Bing Fang Zhi Za Zhi ; 31(4): 414-417, 2019 Sep 26.
Artigo em Chinês | MEDLINE | ID: mdl-31612678

RESUMO

OBJECTIVE: To explore the spatial-temporal distribution of malaria in Jiangxi Province from 1950 to 2017, so as to provide scientific evidence for developing the malaria elimination strategy. METHODS: The epidemic situation of malaria, demographic data, historical species of malaria parasites and transmission vectors were collected from each county of Jiangxi Province from 1950 to 2017 to create a geographic information system database of malaria in Jiangxi Province. The software ArcGIS 10.3 was used to analyze the incidence of malaria and display the spatial-temporal distribution of malaria in Jiangxi Province, so as to explore the spatial-temporal patterns of malaria in the province. RESULTS: From 1950 to 2017, the prevalence of malaria was classified into 3 stages in Jiangxi Province, including the peak period (from 1950 to 1975), the continuous decline period (from 1976 to 1997), and the low-level fluctuation period (from 1998 to 2017). During the period from 1950 through 2017, the incidence of malaria declined, the epidemic area of malaria shrank, and the intensity of malaria transmission gradually reduced to no local infections in Jiangxi Province. The spatial distribution of epidemic areas of malaria shifted from southern mountainous areas to northern plain areas, and finally aggregated, retained and disappeared in plain areas. The species of malaria parasites shifted from a co-endemic area for Plasmodium vivax, P. falciparum and P. malariae to a single endemic area for P. vivax, and finally a co-endemic area for imported P. vivax, P. falciparum, P. malariae and P. ovale. The transmission vectors shifted from multiple vectors of Anopheles sinensis, An. minimus, An. anthropophagus and others to a single vector of An. sinensis. CONCLUSIONS: There are no local malaria cases for successive 6 years since 2012, and the transmission of malaria has been interrupted in Jiangxi Province, in which the criteria for malaria elimination have been achieved. However, the risk of malaria transmission secondary to imported malaria will emerge in Jiangxi Province for a long period of time.


Assuntos
Anopheles , Malária , Animais , China/epidemiologia , Erradicação de Doenças , Malária/epidemiologia , Malária/parasitologia , Malária/transmissão , Mosquitos Vetores/parasitologia , Plasmodium/fisiologia , Prevalência , Fatores de Risco
9.
Malar J ; 18(1): 347, 2019 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-31615576

RESUMO

BACKGROUND: Gene drive mosquitoes have been proposed as a possible means to reduce the transmission of malaria in Africa. Because this technology has no prior use-history at this time, environmental risk assessments for gene drive mosquitoes will benefit from problem formulation-an organized and ordered process to identify protection goals and potential pathways to harm to the environment, or animal or human health. Recognizing this need, the New Partnership for Africa's Development (NEPAD), with support from African and international partners, organized four regional consultative workshops in Africa to initiate this process. METHODS: The workshops were attended by a diverse set of participants and stakeholders, including scientists, ethicists, health professionals, government regulators in the fields of environment health and biosafety as well government policymakers, who met for 4 days to deliberate on protection goals and pathways relevant to the use of gene drive mosquitoes for malaria control. The goal of the workshops was not to produce a comprehensive and detailed environmental risk assessment of gene drive mosquitoes, but rather to introduce problem formulation as a tool to the stakeholder community, and to serve as a starting point for conducting systematic environmental risk assessments in the future, identifying protection goals related to gene drive mosquitoes that are particular to African stakeholders. RESULTS: Participants in the workshops frequently identified human health and biodiversity as being relevant broad protection goals. Results of the deliberations provide insight into the concerns of African participants at an early stage in the development of gene drive organism/products that should be instructive to developers using this technology. CONCLUSIONS: In general, the African participants of the consultations had a precautionary perspective with regard to environmental risk assessment of gene drive technology. As gene drive technology develops, protection goals will become further refined and candidate products will be further defined. These workshops represent only the beginning of a continuing process that will ultimately inform environmental risk assessment for gene drive mosquitoes to control malaria in Africa.


Assuntos
Anopheles/genética , Tecnologia de Impulso Genético/métodos , Controle de Mosquitos/métodos , Mosquitos Vetores/genética , África , Animais , Medição de Risco
10.
Malar J ; 18(1): 345, 2019 Oct 10.
Artigo em Inglês | MEDLINE | ID: mdl-31601226

RESUMO

BACKGROUND: Malaria is a public health problem in the Brazilian Amazon region. In integrated vector management for malaria (anopheline) control, indoor residual spraying (IRS) represents one of the main tools in the basic strategy applied in the Amazonian states. It is essential to understand the residual efficacy of insecticides on different surfaces to determine spray cycles, ensure their rational use, and prevent wastage. This study aimed to evaluate the residual efficacy of six insecticide formulations used in the National Malaria Control Programme on four different types of walls in a field simulation at a "test house". METHODS: The tests were performed as a field-simulating evaluation at a "test house" built in the municipality of Macapá. Six insecticide formulations comprising four pyrethroids, a carbamate, and an organophosphate were used, and evaluated when applied on different wall surfaces: painted wood, unpainted wood, plastered cement, and unplastered cement. The insecticides were applied to the interior walls of the "test house" by a trained technician. RESULTS: In the bioassays performed with pyrethroids, deltamethrin water-dispersible granules (WG) performed particularly well, presenting residual bioefficacy of 8 months on both wood surfaces after the IRS, whereas alpha-cypermethrin suspension concentrate (SC) and etofenprox wettable powder (WP) demonstrated residual bioefficacy of 4 months on at least one of the wood surfaces; however, the pyrethroid lambda-cyhalothrin WP showed a low residual bioefficacy (< 3 months) on all tested surfaces, demonstrating its inefficiency for areas with a long transmission cycle of malaria. For the carbamate-bendiocarb WP, residual bioefficacy for 3 months was achieved only on wood surfaces. In general, the organophosphate pirimifos-methyl capsule suspension (CS) demonstrated the best result, with a mortality rate < 80% over a period of 6 months on all surfaces tested. CONCLUSION: Insecticide efficiency varies among different types of surface; therefore, a "test house" is a valuable evaluation tool. This work highlights the usefulness of associating the residual efficacy of insecticides on the surfaces commonly found in houses in endemic areas, together with knowledge about the transmission cycle duration of the transmission cycle and the insecticide susceptibility of the vector. This association helps in the decision-making for the malaria control intervention regarding.


Assuntos
Anopheles , Inseticidas , Malária/prevenção & controle , Controle de Mosquitos , Mosquitos Vetores , Animais , Brasil , Habitação
11.
Malar J ; 18(1): 335, 2019 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-31570107

RESUMO

BACKGROUND: The decline in malaria cases and vectors is major milestone in fighting against malaria. The efficacy of MAGNet long-lasting insecticidal nets (MAGNet LLIN), an alpha-cypermethrin incorporated long-lasting net, with the target dose ± 25% of 5.8 g active ingredient (AI)/kg (4.35-7.25 g AI/kg) was evaluated in six veranda-trap experimental huts in Muheza, Tanzania against freely flying wild population of Anopheles funestus. METHODS: MAGNet LLINs were tested against wild, free-flying, host-seeking An. funestus mosquitoes over a period of 6 weeks (total of 36 nights in the huts). MAGNet LLIN efficacy was determined in terms of mosquito mortality, blood-feeding inhibition, deterrence, induced exiting, personal protection, and insecticidal killing over 20 washes according to WHO standardized procedures. Efficacy was compared with reference to a WHOPES recommended approved LLINs (DuraNet) and to a net conventionally treated (CTN) treated with alpha-cypermethrin at WHO-recommended dose and washed to just before cut-off point. The efficacy of MAGNet was evaluated in experimental huts against wild, free-flying, pyrethroid-resistant An. funestus. The WHO-susceptibility method was used to detect resistance in wild Anopheles exposed to 0.75% permethrin. Mosquito mortality, blood-feeding inhibition and personal protection were compared between untreated nets and standard LLINs. Blood-feeding rates were recorded and compared between the 20 times washed; blood-feeding rates between 20 times washed MAGNet LLIN and 20 times washed WHOPES-approved piperonyl butoxide (PBO)/pyrethroid were not statistically different (p > 0.05). RESULTS: The results have evidently shown that MAGNet LLIN provides similar blood-feeding inhibition, exophily, mortality, and deterrence to the standard approved LLIN, thus meeting the WHOPES criteria for blood feeding. The significantly high feeding inhibition and personal protection over pyrethroid-resistant An. funestus recorded by both unwashed and 20 times washed MAGNet compared to the unwashed DuraNet, the WHOPES-approved standard pyrethroid-only LLIN provides proof of MAGNet meeting Phase II WHOPES criteria for a LLIN. CONCLUSION: Based on this study, MAGNet has been shown to have a promising impact on protection when 20 times washed against a highly resistant population of An. funestus.


Assuntos
Anopheles , Mosquiteiros Tratados com Inseticida , Inseticidas , Lavanderia , Piretrinas , Animais , Habitação , Resistência a Inseticidas , Controle de Mosquitos/instrumentação , Tanzânia
12.
Malar J ; 18(1): 334, 2019 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-31570113

RESUMO

BACKGROUND: Mosquito saliva elicits immune responses in humans following mosquito blood feeding. Detection of human antibodies recognizing the Anopheles gambiae salivary gland protein 6 (gSG6) or the gSG6-P1 peptide in residents of Africa, South America and Southeast Asia suggested the potential for these antibodies to serve as a universal marker to estimate human biting rates. Validating the utility of this approach requires concurrent comparisons of anopheline biting rates with antibodies to the gSG6 protein to determine the sensitivity and specificity of the assay for monitoring changes in vector populations. This study investigated whether seroprevalence of anti-gSG6 antibodies in humans reflected the relative exposure to Anopheles farauti bites in the Solomon Islands as estimated from sympatric human landing catches. METHODS: Human biting rates by An. farauti were estimated by landing catches at 10 sampling sites in each of 4 villages during the wet and dry seasons. Human serum samples from these same villages were also collected during the wet and dry seasons and analysed for antibody recognition of the gSG6 antigen by the Luminex xMAP© platform. Antibody titres and prevalence were compared to HLCs at the sampling sites nearest to participants' residences for utility of anti-gSG6 antibodies to estimate human exposure to anopheline bites. RESULTS: In this study in the Solomon Islands only 11% of people had very high anti-gSG6 antibody titres, while other individuals did not recognize gSG6 despite nightly exposures of up to 190 bites by An. farauti. Despite clear spatial differences in the human biting rates within and among villages, associations between anti-gSG6 antibody titres and biting rates were not found. CONCLUSIONS: Few studies to date have concurrently measured anopheline biting rates and the prevalence of human antibodies to gSG6. The lack of association between anti-gSG6 antibody titres and concurrently measured human biting rates suggests that the assay for human anti-gSG6 antibodies lacks sufficient sensitivity to be a biomarker of An. farauti exposure at an epidemiologically relevant scale. These findings imply that an improvement in the sensitivity of serology to monitor changes in anopheline biting exposure may require the use of saliva antigens from local anophelines, and this may be especially true for species more distantly related to the African malaria vector An. gambiae.


Assuntos
Anopheles , Imunoglobulina G/sangue , Mordeduras e Picadas de Insetos/imunologia , Proteínas de Insetos/imunologia , Saliva/imunologia , Proteínas e Peptídeos Salivares/imunologia , Animais , Biomarcadores/sangue , Feminino , Humanos , Melanesia , Mosquitos Vetores , Estações do Ano , Estudos Soroepidemiológicos
13.
Malar J ; 18(1): 332, 2019 Sep 30.
Artigo em Inglês | MEDLINE | ID: mdl-31564253

RESUMO

BACKGROUND: Misuse of long-lasting insecticidal nets together with resistance of vectors to most of the insecticides for indoor residual spraying and impregnated nets threaten malaria vector control interventions, requiring search for alternative control methods. Reports have shown that Anopheles mosquitoes die when they feed on endectocidal drugs used to treat humans and animals. A study was designed to investigate the efficacy of LongRange™ (eprinomectin 5%) on laboratory reared Anopheles arabiensis fed on treated calves. METHODS: Anopheles arabiensis from insectary colony was fed on three calves treated with therapeutic dose of LongRange™ eprinomectin (1 ml/50 kg) and on non-treated three other calves as control arm. For the feeding, mosquitoes were placed in paper cups covered with nylon cloth mesh and then allowed to feed on the necks of calves. Subsequently, mosquito survival, fecundity, egg hatchability, larval development and adult emergence were recorded. Data were entered and analysed by using SPSS version 20. The Kaplan-Meier survival analysis and independent sample t-test were used. RESULTS: All mosquitoes that fed on LongRange™ Eprinomectin treated calves died within 7 days following blood ingestion. The drug also slightly affected fecundity and hatchability of An. arabiensis. CONCLUSION: Treating livestock with LongRange™ (eprinomectin 5%) may serve as a supplementary control method for zoophagic An. arabiensis.


Assuntos
Anopheles , Inseticidas/administração & dosagem , Ivermectina/análogos & derivados , Controle de Mosquitos/métodos , Animais , Bioensaio , Bovinos , Comportamento Alimentar , Fertilidade , Injeções Subcutâneas , Ivermectina/administração & dosagem , Gado , Malária/transmissão , Mosquitos Vetores
14.
Nature ; 574(7778): 340-341, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31611682
15.
Malar J ; 18(1): 311, 2019 Sep 14.
Artigo em Inglês | MEDLINE | ID: mdl-31521176

RESUMO

BACKGROUND: Malaria remains one of the most important causes of morbidity and death in sub-Saharan Africa. Along with early diagnosis and treatment of malaria cases and intermittent preventive treatment in pregnancy (IPTp), vector control is an important tool in the reduction of new cases. Alongside the use of long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS), targeting the vector larvae with biological larvicides, such as Bacillus thuringiensis israelensis (Bti) is gaining importance as a means of reducing the number of mosquito larvae before they emerge to their adult stage. This study presents data corroborating the entomological impact of such an intervention in a rural African environment. METHODS: The study extended over 2 years and researched the impact of biological larviciding with Bti on malaria mosquitoes that were caught indoors and outdoors of houses using light traps. The achieved reductions in female Anopheles mosquitoes were calculated for two different larviciding choices using a regression model. RESULTS: In villages that received selective treatment of the most productive breeding sites, the number of female Anopheles spp. dropped by 61% (95% CI 54-66%) compared to the pre-intervention period. In villages in which all breeding sites were treated, the number of female Anopheles spp. was reduced by 70% (95% CI 64-74%) compared to the pre-intervention period. CONCLUSION: It was shown that malaria vector abundance can be dramatically reduced through larviciding of breeding habitats and that, in many geographical settings, they are a viable addition to current malaria control measures.


Assuntos
Anopheles , Bacillus thuringiensis/química , Inseticidas/uso terapêutico , Controle de Mosquitos/métodos , Mosquitos Vetores , Controle Biológico de Vetores/métodos , Animais , Anopheles/crescimento & desenvolvimento , Burkina Faso , Feminino , Larva/crescimento & desenvolvimento , Mosquitos Vetores/crescimento & desenvolvimento
16.
Nat Commun ; 10(1): 4300, 2019 09 20.
Artigo em Inglês | MEDLINE | ID: mdl-31541097

RESUMO

Mainstay treatment for Plasmodium vivax malaria has long relied on chloroquine (CQ) against blood-stage parasites plus primaquine against dormant liver-stage forms (hypnozoites), however drug resistance confronts this regimen and threatens malaria control programs. Understanding the basis of P. vivax chloroquine resistance (CQR) will inform drug discovery and malaria control. Here we investigate the genetics of P. vivax CQR by a cross of parasites differing in drug response. Gametocytogenesis, mosquito infection, and progeny production are performed with mixed parasite populations in nonhuman primates, as methods for P. vivax cloning and in vitro cultivation remain unavailable. Linkage mapping of progeny surviving >15 mg/kg CQ identifies a 76 kb region in chromosome 1 including pvcrt, an ortholog of the Plasmodium falciparum CQR transporter gene. Transcriptional analysis supports upregulated pvcrt expression as a mechanism of CQR.


Assuntos
Antimaláricos/farmacologia , Cloroquina/farmacologia , Cruzamentos Genéticos , Resistência a Medicamentos/genética , Proteínas de Membrana Transportadoras/genética , Plasmodium vivax/efeitos dos fármacos , Plasmodium vivax/genética , Proteínas de Protozoários/genética , Animais , Anopheles/parasitologia , Culicidae/parasitologia , Descoberta de Drogas , Feminino , Expressão Gênica , Genes de Protozoários , Malária/tratamento farmacológico , Malária Vivax/tratamento farmacológico , Malária Vivax/parasitologia , Masculino , Plasmodium falciparum/genética
17.
Nat Commun ; 10(1): 4298, 2019 09 20.
Artigo em Inglês | MEDLINE | ID: mdl-31541102

RESUMO

Insecticidal fungi represent a promising alternative to chemical pesticides for disease vector control. Here, we show that the pathogenic fungus Beauveria bassiana exports a microRNA-like RNA (bba-milR1) that hijacks the host RNA-interference machinery in mosquito cells by binding to Argonaute 1 (AGO1). bba-milR1 is highly expressed during fungal penetration of the mosquito integument, and suppresses host immunity by silencing expression of the mosquito Toll receptor ligand Spätzle 4 (Spz4). Later, upon entering the hemocoel, bba-milR1 expression is decreased, which avoids induction of the host proteinase CLIPB9 that activates the melanization response. Thus, our results indicate that the pathogen deploys a cross-kingdom small-RNA effector that attenuates host immunity and facilitates infection.


Assuntos
Beauveria/imunologia , Interações Hospedeiro-Patógeno/imunologia , MicroRNAs/metabolismo , Mosquitos Vetores/imunologia , Mosquitos Vetores/microbiologia , Animais , Anopheles/imunologia , Anopheles/microbiologia , Beauveria/patogenicidade , Feminino , Perfilação da Expressão Gênica , Sistema Imunitário/imunologia , Proteínas de Insetos/genética , Proteínas de Insetos/metabolismo , Malária/imunologia , Controle Biológico de Vetores , Interferência de RNA , RNA de Cadeia Dupla
18.
Parasit Vectors ; 12(1): 446, 2019 Sep 11.
Artigo em Inglês | MEDLINE | ID: mdl-31506104

RESUMO

BACKGROUND: The recent resurgence of interest in sterile insect techniques to control vector mosquitoes has renewed interest in novel methods for observing mating behavior. Malarial vectors of the Anopheles gambiae complex are known to mate in swarms at specific locations at dawn and dusk. Most knowledge of mosquito swarming behavior is derived from field observations and a few experimental studies designed to assess critical parameters that affect mosquito swarming. However, such studies are difficult to implement in the field because of uncontrollable environmental factors and mosquito conditions. Here, we present two experimental setups specifically designed to analyze mosquito swarming behavior and provide evidence that swarming behavior of mosquitoes can be generated and accurately assessed under both semi-field and laboratory conditions. METHODS: The Mosquito Ecology Research Facility setup is a semi-field enclosure made of 12 compartments (10.0 × 6.0 × 4.5 m L × W × H each) exposed to ambient meteorological and lighting conditions. The laboratory setup consists of a windowless room (5.1 × 4.7 × 3.0 m) in which both environmental and mosquito conditions can be controlled. In the two setups, 300 3-6-days-old An. coluzzii virgin males were released and some swarm characteristics were recorded such as the time at which the swarm started, the number of mosquitoes in the swarm and the height. Climatic conditions in the semi-field setup were also recorded. RESULTS: In both setups, An. coluzzii males displayed stereotyped and consistent swarming behavior day after day; males gradually gather into a swarm over a ground marker at sunset, flying in loops in relation to specific visual features on the ground. Although semi-field climatic conditions were slightly different from outdoors conditions, they did not impede swarming behavior and swarm characteristics were similar to those observed in the field. CONCLUSIONS: Swarm characteristics and their consistency across days provide evidences that these facilities can be used confidently to study swarming behavior. These facilities come to complement existing semi-field setups and pave the way for new experimental studies which will enhance our understanding of mating behavior but also mosquito ecology and evolution, a prerequisite for application of genetic approaches to malaria control.


Assuntos
Anopheles/fisiologia , Entomologia/métodos , Mosquitos Vetores/fisiologia , Comportamento Sexual Animal , Animais
19.
BMC Infect Dis ; 19(1): 800, 2019 Sep 11.
Artigo em Inglês | MEDLINE | ID: mdl-31510931

RESUMO

BACKGROUND: Larviciding is an effective supplementary tool for malaria vector control, but the identification and accessibility of aquatic habitats impedes application. Dissemination of the insect growth regulator, pyriproxyfen (PPF), by gravid Anopheles might constitute a novel application strategy. This study aimed to explore the feasibility of using an attractive bait-station to contaminate gravid Anopheles gambiae sensu stricto with PPF and subsequently transfer PPF to larval habitats. METHODS: A bait-station was developed comprising of an artificial pond containing water treated with 20 ppm cedrol, an oviposition attractant, and a netting-cover treated with PPF. Three identical semi-field cages were used to assess the potential of gravid Anopheles to transfer PPF from the bait-station to ponds. Gravid females were released in two semi-field cages, one with PPF on its bait-station (test) and one without PPF (control). No mosquitoes were released in the third cage with a PPF-treated station (control). Transfer of PPF to open ponds was assessed by monitoring emergence of late instar insectary-reared larvae introduced into the ponds. The amount of PPF carried by a mosquito and transferred to water was quantified using liquid chromatography-mass spectrometry. RESULTS: In the controls, 86% (95% CI 81-89%) of larvae introduced into open ponds developed into adults, indicating that wind did not distribute PPF in absence of mosquitoes. Emergence inhibition was observed in the test cage but was dependent on the distance between pond and bait-station. Only 25% (95% CI 22-29%) of larvae emerged as adults from ponds 4 m from the bait-station, but 92% (95% CI 89-94%) emerged from ponds 10 m away. Each mosquito was contaminated on average with 112 µg (95% CI 93-123 µg) PPF resulting in the transfer of 230 ng/L (95% CI 180-290 ng/L) PPF to 100 ml volumes of water. CONCLUSIONS: The bait-stations successfully attracted gravid females which were subsequently dusted with effective levels of PPF. However, in this study design, attraction and dissemination was limited to short distances. To make this approach feasible for malaria vector control, stronger attractants that lure gravid females from longer distances, in landscapes with many water bodies, and better PPF delivery systems are needed.


Assuntos
Anopheles/efeitos dos fármacos , Inseticidas/toxicidade , Controle de Mosquitos/métodos , Piridinas/toxicidade , Animais , Anopheles/crescimento & desenvolvimento , Anopheles/fisiologia , Feminino , Larva/efeitos dos fármacos , Oviposição , Tanques , Terpenos/farmacologia
20.
Malar J ; 18(1): 322, 2019 Sep 23.
Artigo em Inglês | MEDLINE | ID: mdl-31547828

RESUMO

BACKGROUND: This paper outlines Zimbabwe's potential readiness in harnessing integrated vector management (IVM) strategy for enhanced control of vector-borne diseases. The objective is to provide guidance for the country in the implementation of the national IVM strategy in order to make improvements required in thematic areas of need. The paper also assesses the existing opportunities and gaps to promote and adopt the approach as a national policy. MAIN TEXT: Despite recent gains in combating vector-borne diseases, especially malaria, management of vector control programmes still remains insecticide-based and vertical in nature. Therefore, concerns have been raised on whether the current long-standing conventional vector control strategy still remains with sufficient action to continue to break the transmission cycle to the levels of elimination. This is so, given the continuous dwindling resources for vector control, changes in vector behaviour, the emergence of resistance to medicines and insecticides, climate change, environmental degradation, as well as diversity in ecology, breeding habitats, and community habits. Cognizant of all that, elements of a surveillance-driven IVM approach are rapidly needed to move vector control interventions a step further. These include advocacy, policy formulation, capacity building, public and private partnerships, community engagement, and increasingly basing decisions on local evidence. Understanding the existing opportunities and gaps, and the recognition that some elements of IVM are already imbedded in the current health programmes is important to encourage stakeholders to promptly support its implementation. Leveraging on the existing opportunities, combined with sufficient advocacy, IVM could easily be accepted by the Zimbabwe government as part of a wider integrated disease management strategy. The strategy could represent an excellent breakthrough to establish much needed intra and inter-sectoral dialogue, and coordination for improved vector-borne disease prevention. CONCLUSIONS: After synthesis of the opportunities and challenges clearly presented, it was concluded that it is imperative for Zimbabwe to adopt and implement IVM strategy that is informed by work already done, while addressing the bottlenecks. The significance of refocusing for improved disease prevention that has the potential to accomplish elimination of not only malaria but all vector borne diseases much earlier than anticipated under the existing vector control system is underscored.


Assuntos
Anopheles , Controle de Doenças Transmissíveis/legislação & jurisprudência , Política de Saúde/legislação & jurisprudência , Malária/prevenção & controle , Controle de Mosquitos/métodos , Mosquitos Vetores , Animais , Zimbábue
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