Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 174
Filtrar
2.
Parasit Vectors ; 17(1): 261, 2024 Jun 17.
Artigo em Inglês | MEDLINE | ID: mdl-38886827

RESUMO

BACKGROUND: Malaria transmission in Tanzania is driven by mosquitoes of the Anopheles gambiae complex and Anopheles funestus group. The latter includes An. funestus s.s., an anthropophilic vector, which is now strongly resistant to public health insecticides, and several sibling species, which remain largely understudied despite their potential as secondary vectors. This paper provides the initial results of a cross-country study of the species composition, distribution and malaria transmission potential of members of the Anopheles funestus group in Tanzania. METHODS: Mosquitoes were collected inside homes in 12 regions across Tanzania between 2018 and 2022 using Centres for Disease Control and Prevention (CDC) light traps and Prokopack aspirators. Polymerase chain reaction (PCR) assays targeting the noncoding internal transcribed spacer 2 (ITS2) and 18S ribosomal DNA (18S rDNA) were used to identify sibling species in the An. funestus group and presence of Plasmodium infections, respectively. Where DNA fragments failed to amplify during PCR, we sequenced the ITS2 region to identify any polymorphisms. RESULTS: The following sibling species of the An. funestus group were found across Tanzania: An. funestus s.s. (50.3%), An. parensis (11.4%), An. rivulorum (1.1%), An. leesoni (0.3%). Sequencing of the ITS2 region in the nonamplified samples showed that polymorphisms at the priming sites of standard species-specific primers obstructed PCR amplification, although the ITS2 sequences closely matched those of An. funestus s.s., barring these polymorphisms. Of the 914 samples tested for Plasmodium infections, 11 An. funestus s.s. (1.2%), and 2 An. parensis (0.2%) individuals were confirmed positive for P. falciparum. The highest malaria transmission intensities [entomological inoculation rate (EIR)] contributed by the Funestus group were in the north-western region [108.3 infectious bites/person/year (ib/p/y)] and the south-eastern region (72.2 ib/p/y). CONCLUSIONS: Whereas An. funestus s.s. is the dominant malaria vector in the Funestus group in Tanzania, this survey confirms the occurrence of Plasmodium-infected An. parensis, an observation previously made in at least two other occasions in the country. The findings indicate the need to better understand the ecology and vectorial capacity of this and other secondary malaria vectors in the region to improve malaria control.


Assuntos
Anopheles , Malária , Mosquitos Vetores , Anopheles/genética , Anopheles/classificação , Anopheles/parasitologia , Anopheles/fisiologia , Animais , Tanzânia/epidemiologia , Mosquitos Vetores/genética , Mosquitos Vetores/parasitologia , Mosquitos Vetores/classificação , Mosquitos Vetores/fisiologia , Malária/transmissão , Malária/epidemiologia , Humanos , RNA Ribossômico 18S/genética , Reação em Cadeia da Polimerase , Feminino , Plasmodium/genética , Plasmodium/isolamento & purificação , Plasmodium/classificação , DNA Espaçador Ribossômico/genética
3.
bioRxiv ; 2024 May 29.
Artigo em Inglês | MEDLINE | ID: mdl-38854026

RESUMO

A major mechanism of insecticide resistance in insect pests is knock-down resistance (kdr) caused by mutations in the voltage-gated sodium channel (Vgsc) gene. Despite being common in most malaria Anopheles vector species, kdr mutations have never been observed in Anopheles funestus, the principal malaria vector in Eastern and Southern Africa. While monitoring 10 populations of An. funestus in Tanzania, we unexpectedly found resistance to DDT, a banned insecticide, in one location. Through whole-genome sequencing of 333 An. funestus samples from these populations, we found 8 novel amino acid substitutions in the Vgsc gene, including the kdr variant, L976F (L1014F in An. gambiae), in tight linkage disequilibrium with another (P1842S). The mutants were found only at high frequency in one region, with a significant decline between 2017 and 2023. Notably, kdr L976F was strongly associated with survivorship to the exposure to DDT insecticide, while no clear association was noted with a pyrethroid insecticide (deltamethrin). Further study is necessary to identify the origin and spread of kdr in An. funestus, and the potential threat to current insecticide-based vector control in Africa.

4.
Malar J ; 23(1): 188, 2024 Jun 17.
Artigo em Inglês | MEDLINE | ID: mdl-38880870

RESUMO

BACKGROUND: Effective testing for malaria, including the detection of infections at very low densities, is vital for the successful elimination of the disease. Unfortunately, existing methods are either inexpensive but poorly sensitive or sensitive but costly. Recent studies have shown that mid-infrared spectroscopy coupled with machine learning (MIRs-ML) has potential for rapidly detecting malaria infections but requires further evaluation on diverse samples representative of natural infections in endemic areas. The aim of this study was, therefore, to demonstrate a simple AI-powered, reagent-free, and user-friendly approach that uses mid-infrared spectra from dried blood spots to accurately detect malaria infections across varying parasite densities and anaemic conditions. METHODS: Plasmodium falciparum strains NF54 and FCR3 were cultured and mixed with blood from 70 malaria-free individuals to create various malaria parasitaemia and anaemic conditions. Blood dilutions produced three haematocrit ratios (50%, 25%, 12.5%) and five parasitaemia levels (6%, 0.1%, 0.002%, 0.00003%, 0%). Dried blood spots were prepared on Whatman™ filter papers and scanned using attenuated total reflection-Fourier Transform Infrared (ATR-FTIR) for machine-learning analysis. Three classifiers were trained on an 80%/20% split of 4655 spectra: (I) high contrast (6% parasitaemia vs. negative), (II) low contrast (0.00003% vs. negative) and (III) all concentrations (all positive levels vs. negative). The classifiers were validated with unseen datasets to detect malaria at various parasitaemia levels and anaemic conditions. Additionally, these classifiers were tested on samples from a population survey in malaria-endemic villages of southeastern Tanzania. RESULTS: The AI classifiers attained over 90% accuracy in detecting malaria infections as low as one parasite per microlitre of blood, a sensitivity unattainable by conventional RDTs and microscopy. These laboratory-developed classifiers seamlessly transitioned to field applicability, achieving over 80% accuracy in predicting natural P. falciparum infections in blood samples collected during the field survey. Crucially, the performance remained unaffected by various levels of anaemia, a common complication in malaria patients. CONCLUSION: These findings suggest that the AI-driven mid-infrared spectroscopy approach holds promise as a simplified, sensitive and cost-effective method for malaria screening, consistently performing well despite variations in parasite densities and anaemic conditions. The technique simply involves scanning dried blood spots with a desktop mid-infrared scanner and analysing the spectra using pre-trained AI classifiers, making it readily adaptable to field conditions in low-resource settings. In this study, the approach was successfully adapted to field use, effectively predicting natural malaria infections in blood samples from a population-level survey in Tanzania. With additional field trials and validation, this technique could significantly enhance malaria surveillance and contribute to accelerating malaria elimination efforts.


Assuntos
Malária Falciparum , Plasmodium falciparum , Humanos , Malária Falciparum/diagnóstico , Malária Falciparum/sangue , Malária Falciparum/parasitologia , Plasmodium falciparum/isolamento & purificação , Parasitemia/diagnóstico , Parasitemia/parasitologia , Anemia/diagnóstico , Anemia/sangue , Anemia/parasitologia , Espectrofotometria Infravermelho/métodos , Aprendizado de Máquina , Carga Parasitária , Adulto , Inteligência Artificial , Sensibilidade e Especificidade , Feminino , Adulto Jovem , Espectroscopia de Infravermelho com Transformada de Fourier/métodos , Adolescente , Masculino , Pessoa de Meia-Idade , Programas de Rastreamento/métodos
5.
Trop Med Infect Dis ; 9(5)2024 Apr 25.
Artigo em Inglês | MEDLINE | ID: mdl-38787029

RESUMO

Childhood undernutrition is a major issue in low- and middle-income countries, affecting the health, well-being, and educational outcomes of schoolchildren. This study aimed to assess the prevalence and associated factors of stunting, wasting, and underweight among schoolchildren in peri-urban areas in the south-eastern part of Tanzania. A cross-sectional study was conducted involving 930 children aged 6-12 years from four primary schools from July to August 2019. The WHO Anthro Survey Analyzer was employed to estimate the prevalence of stunting, wasting, and underweight, while logistic regression analyses examined sociodemographic background, malaria infection, anaemia, anthropometric measures, and dietary diversity score as potential factors. The prevalence of stunting, wasting, underweight, overweight, and obesity was 11.8%, 4.3%, 3.9%, 11.1%, and 2.0%, respectively. Overall, 1.5% of the children had malaria, as determined by rapid diagnostic tests, and 0.4% had severe anaemia. Univariate analysis indicated higher odds of undernutrition among children aged 9-12 compared to their younger peers. Stunting was more common among children with low and medium dietary diversity. Anaemia was found in 11.2% of schoolchildren, and severe anaemia was associated with wasting. Multivariate analysis revealed that age and low dietary diversity were significantly associated with undernutrition. These findings emphasise the need for school-based health and nutrition programmes targeting children beyond the age of 5 to improve their nutritional status and mitigate potential adverse effects on health, cognition, and academic achievement. Regular assessment of the nutritional status of schoolchildren is warranted.

6.
Parasit Vectors ; 17(1): 230, 2024 May 17.
Artigo em Inglês | MEDLINE | ID: mdl-38760849

RESUMO

BACKGROUND: Anopheles funestus is a leading vector of malaria in most parts of East and Southern Africa, yet its ecology and responses to vector control remain poorly understood compared with other vectors such as Anopheles gambiae and Anopheles arabiensis. This study presents the first large-scale survey of the genetic and phenotypic expression of insecticide resistance in An. funestus populations in Tanzania. METHODS: We performed insecticide susceptibility bioassays on An. funestus mosquitoes in nine regions with moderate-to-high malaria prevalence in Tanzania, followed by genotyping for resistance-associated mutations (CYP6P9a, CYP6P9b, L119F-GSTe2) and structural variants (SV4.3 kb, SV6.5 kb). Generalized linear models were used to assess relationships between genetic markers and phenotypic resistance. An interactive R Shiny tool was created to visualize the data and support evidence-based interventions. RESULTS: Pyrethroid resistance was universal but reversible by piperonyl-butoxide (PBO). However, carbamate resistance was observed in only five of the nine districts, and dichloro-diphenyl-trichloroethane (DDT) resistance was found only in the Kilombero valley, south-eastern Tanzania. Conversely, there was universal susceptibility to the organophosphate pirimiphos-methyl in all sites. Genetic markers of resistance had distinct geographical patterns, with CYP6P9a-R and CYP6P9b-R alleles, and the SV6.5 kb structural variant absent or undetectable in the north-west but prevalent in all other sites, while SV4.3 kb was prevalent in the north-western and western regions but absent elsewhere. Emergent L119F-GSTe2, associated with deltamethrin resistance, was detected in heterozygous form in districts bordering Mozambique, Malawi and the Democratic Republic of Congo. The resistance landscape was most complex in western Tanzania, in Tanganyika district, where all five genetic markers were detected. There was a notable south-to-north spread of resistance genes, especially CYP6P9a-R, though this appears to be interrupted, possibly by the Rift Valley. CONCLUSIONS: This study underscores the need to expand resistance monitoring to include An. funestus alongside other vector species, and to screen for both the genetic and phenotypic signatures of resistance. The findings can be visualized online via an interactive user interface and could inform data-driven decision-making for resistance management and vector control. Since this was the first large-scale survey of resistance in Tanzania's An. funestus, we recommend regular updates with greater geographical and temporal coverage.


Assuntos
Anopheles , Resistência a Inseticidas , Inseticidas , Malária , Mosquitos Vetores , Animais , Anopheles/genética , Anopheles/efeitos dos fármacos , Resistência a Inseticidas/genética , Tanzânia/epidemiologia , Mosquitos Vetores/genética , Mosquitos Vetores/efeitos dos fármacos , Inseticidas/farmacologia , Malária/transmissão , Malária/epidemiologia , Marcadores Genéticos , Piretrinas/farmacologia , Genótipo , Mutação
7.
Sci Rep ; 14(1): 12100, 2024 05 27.
Artigo em Inglês | MEDLINE | ID: mdl-38802488

RESUMO

Field-derived metrics are critical for effective control of malaria, particularly in sub-Saharan Africa where the disease kills over half a million people yearly. One key metric is entomological inoculation rate, a direct measure of transmission intensities, computed as a product of human biting rates and prevalence of Plasmodium sporozoites in mosquitoes. Unfortunately, current methods for identifying infectious mosquitoes are laborious, time-consuming, and may require expensive reagents that are not always readily available. Here, we demonstrate the first field-application of mid-infrared spectroscopy and machine learning (MIRS-ML) to swiftly and accurately detect Plasmodium falciparum sporozoites in wild-caught Anopheles funestus, a major Afro-tropical malaria vector, without requiring any laboratory reagents. We collected 7178 female An. funestus from rural Tanzanian households using CDC-light traps, then desiccated and scanned their heads and thoraces using an FT-IR spectrometer. The sporozoite infections were confirmed using enzyme-linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR), to establish references for training supervised algorithms. The XGBoost model was used to detect sporozoite-infectious specimen, accurately predicting ELISA and PCR outcomes with 92% and 93% accuracies respectively. These findings suggest that MIRS-ML can rapidly detect P. falciparum in field-collected mosquitoes, with potential for enhancing surveillance in malaria-endemic regions. The technique is both fast, scanning 60-100 mosquitoes per hour, and cost-efficient, requiring no biochemical reactions and therefore no reagents. Given its previously proven capability in monitoring key entomological indicators like mosquito age, human blood index, and identities of vector species, we conclude that MIRS-ML could constitute a low-cost multi-functional toolkit for monitoring malaria risk and evaluating interventions.


Assuntos
Anopheles , Aprendizado de Máquina , Malária Falciparum , Mosquitos Vetores , Plasmodium falciparum , Animais , Anopheles/parasitologia , Malária Falciparum/epidemiologia , Malária Falciparum/diagnóstico , Malária Falciparum/parasitologia , Plasmodium falciparum/isolamento & purificação , Mosquitos Vetores/parasitologia , Feminino , Humanos , Tanzânia/epidemiologia , Esporozoítos , Espectrofotometria Infravermelho/métodos , Espectroscopia de Infravermelho com Transformada de Fourier/métodos
8.
Int J Health Geogr ; 23(1): 13, 2024 May 19.
Artigo em Inglês | MEDLINE | ID: mdl-38764024

RESUMO

BACKGROUND: In the near future, the incidence of mosquito-borne diseases may expand to new sites due to changes in temperature and rainfall patterns caused by climate change. Therefore, there is a need to use recent technological advances to improve vector surveillance methodologies. Unoccupied Aerial Vehicles (UAVs), often called drones, have been used to collect high-resolution imagery to map detailed information on mosquito habitats and direct control measures to specific areas. Supervised classification approaches have been largely used to automatically detect vector habitats. However, manual data labelling for model training limits their use for rapid responses. Open-source foundation models such as the Meta AI Segment Anything Model (SAM) can facilitate the manual digitalization of high-resolution images. This pre-trained model can assist in extracting features of interest in a diverse range of images. Here, we evaluated the performance of SAM through the Samgeo package, a Python-based wrapper for geospatial data, as it has not been applied to analyse remote sensing images for epidemiological studies. RESULTS: We tested the identification of two land cover classes of interest: water bodies and human settlements, using different UAV acquired imagery across five malaria-endemic areas in Africa, South America, and Southeast Asia. We employed manually placed point prompts and text prompts associated with specific classes of interest to guide the image segmentation and assessed the performance in the different geographic contexts. An average Dice coefficient value of 0.67 was obtained for buildings segmentation and 0.73 for water bodies using point prompts. Regarding the use of text prompts, the highest Dice coefficient value reached 0.72 for buildings and 0.70 for water bodies. Nevertheless, the performance was closely dependent on each object, landscape characteristics and selected words, resulting in varying performance. CONCLUSIONS: Recent models such as SAM can potentially assist manual digitalization of imagery by vector control programs, quickly identifying key features when surveying an area of interest. However, accurate segmentation still requires user-provided manual prompts and corrections to obtain precise segmentation. Further evaluations are necessary, especially for applications in rural areas.


Assuntos
Mudança Climática , Humanos , Animais , Malária/epidemiologia , Mosquitos Vetores , Tecnologia de Sensoriamento Remoto/métodos , Sistemas de Informação Geográfica , Processamento de Imagem Assistida por Computador/métodos
9.
Malar J ; 23(1): 86, 2024 Mar 26.
Artigo em Inglês | MEDLINE | ID: mdl-38532415

RESUMO

BACKGROUND: The degree to which Anopheles mosquitoes prefer biting humans over other vertebrate hosts, i.e. the human blood index (HBI), is a crucial parameter for assessing malaria transmission risk. However, existing techniques for identifying mosquito blood meals are demanding in terms of time and effort, involve costly reagents, and are prone to inaccuracies due to factors such as cross-reactivity with other antigens or partially digested blood meals in the mosquito gut. This study demonstrates the first field application of mid-infrared spectroscopy and machine learning (MIRS-ML), to rapidly assess the blood-feeding histories of malaria vectors, with direct comparison to PCR assays. METHODS AND RESULTS: Female Anopheles funestus mosquitoes (N = 1854) were collected from rural Tanzania and desiccated then scanned with an attenuated total reflectance Fourier-transform Infrared (ATR-FTIR) spectrometer. Blood meals were confirmed by PCR, establishing the 'ground truth' for machine learning algorithms. Logistic regression and multi-layer perceptron classifiers were employed to identify blood meal sources, achieving accuracies of 88%-90%, respectively, as well as HBI estimates aligning well with the PCR-based standard HBI. CONCLUSIONS: This research provides evidence of MIRS-ML effectiveness in classifying blood meals in wild Anopheles funestus, as a potential complementary surveillance tool in settings where conventional molecular techniques are impractical. The cost-effectiveness, simplicity, and scalability of MIRS-ML, along with its generalizability, outweigh minor gaps in HBI estimation. Since this approach has already been demonstrated for measuring other entomological and parasitological indicators of malaria, the validation in this study broadens its range of use cases, positioning it as an integrated system for estimating pathogen transmission risk and evaluating the impact of interventions.


Assuntos
Anopheles , Malária , Animais , Humanos , Feminino , Mosquitos Vetores , Malária/epidemiologia , Aprendizado de Máquina , Espectrofotometria Infravermelho , Comportamento Alimentar
11.
Parasit Vectors ; 17(1): 143, 2024 Mar 18.
Artigo em Inglês | MEDLINE | ID: mdl-38500231

RESUMO

BACKGROUND: Accurately determining the age and survival probabilities of adult mosquitoes is crucial for understanding parasite transmission, evaluating the effectiveness of control interventions and assessing disease risk in communities. This study was aimed at demonstrating the rapid identification of epidemiologically relevant age categories of Anopheles funestus, a major Afro-tropical malaria vector, through the innovative combination of infrared spectroscopy and machine learning, instead of the cumbersome practice of dissecting mosquito ovaries to estimate age based on parity status. METHODS: Anopheles funestus larvae were collected in rural south-eastern Tanzania and reared in an insectary. Emerging adult females were sorted by age (1-16 days old) and preserved using silica gel. Polymerase chain reaction (PCR) confirmation was conducted using DNA extracted from mosquito legs to verify the presence of An. funestus and to eliminate undesired mosquitoes. Mid-infrared spectra were obtained by scanning the heads and thoraces of the mosquitoes using an attenuated total reflection-Fourier transform infrared (ATR-FT-IR) spectrometer. The spectra (N = 2084) were divided into two epidemiologically relevant age groups: 1-9 days (young, non-infectious) and 10-16 days (old, potentially infectious). The dimensionality of the spectra was reduced using principal component analysis, and then a set of machine learning and multi-layer perceptron (MLP) models were trained using the spectra to predict the mosquito age categories. RESULTS: The best-performing model, XGBoost, achieved overall accuracy of 87%, with classification accuracy of 89% for young and 84% for old An. funestus. When the most important spectral features influencing the model performance were selected to train a new model, the overall accuracy increased slightly to 89%. The MLP model, utilizing the significant spectral features, achieved higher classification accuracy of 95% and 94% for the young and old An. funestus, respectively. After dimensionality reduction, the MLP achieved 93% accuracy for both age categories. CONCLUSIONS: This study shows how machine learning can quickly classify epidemiologically relevant age groups of An. funestus based on their mid-infrared spectra. Having been previously applied to An. gambiae, An. arabiensis and An. coluzzii, this demonstration on An. funestus underscores the potential of this low-cost, reagent-free technique for widespread use on all the major Afro-tropical malaria vectors. Future research should demonstrate how such machine-derived age classifications in field-collected mosquitoes correlate with malaria in human populations.


Assuntos
Anopheles , Malária , Animais , Feminino , Humanos , Lactente , Pré-Escolar , Criança , Recém-Nascido , Anopheles/parasitologia , Mosquitos Vetores/parasitologia , Espectroscopia de Infravermelho com Transformada de Fourier , Tanzânia
12.
Int J Public Health ; 69: 1606267, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-38481704

RESUMO

Objectives: This Delphi study intended to develop competencies for transformational leadership in public health, including behavioral descriptions (descriptors) tailored to individuals and their contexts. Methods: The study involved five rounds, including online "e-Delphi" consultations and real-time online workshops with experts from diverse sectors. Relevant competencies were identified through a literature review, and experts rated, ranked, rephrased, and proposed descriptors. The study followed the Guidance on Conducting and REporting DElphi Studies (CREDES) and the COmpeteNcy FramEwoRk Development in Health Professions (CONFERD-HP) reporting guidelines. Results: Our framework comprises ten competencies for transformational public health leadership (each with its descriptors) within four categories, and also describes a four-stage model for developing relevant competencies tailored to different contexts. Conclusion: Educators responsible for curriculum design, particularly those aiming to align curricula with local goals, making leadership education context-specific and -sensitive, may benefit from the proposed framework. Additionally, it can help strengthen links between education and workforce sectors, address competency gaps, and potentially reduce the out-migration of graduates in the health professions.


Assuntos
Liderança , Saúde Pública , Humanos , Competência Clínica , Currículo , Técnica Delphi , Competência Profissional
13.
Med Vet Entomol ; 38(2): 119-137, 2024 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-38303659

RESUMO

There has been significant progress in malaria control in the last 2 decades, with a decline in mortality and morbidity. However, these gains are jeopardised by insecticide resistance, which negatively impacts the core interventions, such as insecticide-treated nets (ITN) and indoor residual spraying (IRS). While most malaria control and research efforts are still focused on Anopheles gambiae complex mosquitoes, Anopheles funestus remains an important vector in many countries and, in some cases, contributes to most of the local transmission. As countries move towards malaria elimination, it is important to ensure that all dominant vector species, including An. funestus, an important vector in some countries, are targeted. The objective of this review is to compile and discuss information related to A. funestus populations' resistance to insecticides and the mechanisms involved across Africa, emphasising the sibling species and their resistance profiles in relation to malaria elimination goals. Data on insecticide resistance in An. funestus malaria vectors in Africa were extracted from published studies. Online bibliographic databases, including Google Scholar and PubMed, were used to search for relevant studies. Articles published between 2000 and May 2023 reporting resistance of An. funestus to insecticides and associated mechanisms were included. Those reporting only bionomics were excluded. Spatial variation in species distribution and resistance to insecticides was recorded from 174 articles that met the selection criteria. It was found that An. funestus was increasingly resistant to the four classes of insecticides recommended by the World Health Organisation for malaria vector control; however, this varied by country. Insecticide resistance appears to reduce the effectiveness of vector control methods, particularly IRS and ITN. Biochemical resistance due to detoxification enzymes (P450s and glutathione-S-transferases [GSTs]) in An. funestus was widely recorded. However, An. funestus in Africa remains susceptible to other insecticide classes, such as organophosphates and neonicotinoids. This review highlights the increasing insecticide resistance of An. funestus mosquitoes, which are important malaria vectors in Africa, posing a significant challenge to malaria control efforts. While An. funestus has shown resistance to the recommended insecticide classes, notably pyrethroids and, in some cases, organochlorides and carbamates, it remains susceptible to other classes of insecticides such as organophosphates and neonicotinoids, providing potential alternative options for vector control strategies. The study underscores the need for targeted interventions that consider the population structure and geographical distribution of An. funestus, including its sibling species and their insecticide resistance profiles, to effectively achieve malaria elimination goals.


Des progrès importants ont été réalisés dans le contrôle du paludisme au cours des deux dernières décennies, qui se traduisent par une baisse de la mortalité et de la morbidité. Cependant, ces gains sont compromis par la résistance aux insecticides, ce qui a un impact négatif sur les interventions de base, telles que les moustiquaires imprégnées d'insecticides et la pulvérisation intradomicilliare (PID). Alors que la plupart des efforts de contrôle et de recherche sur le paludisme sont toujours axés sur les moustiques du complexes Anopheles gambiae, Anopheles funestus reste un vecteur important dans de nombreux pays et, dans certains cas, contribue à la majeure partie de la transmission locale. Au moment où certains pays se dirigent vers l'élimination du paludisme, il serait important de prendre en considération toutes les espèces vectrices dominantes, y compris An. funestus. L'objectif de cette revue est de compiler et de discuter des informations liées à la résistance des populations d'An. funestus aux insecticides et les mécanismes impliqués à travers l'Afrique, en mettant l'accent sur les sous espèces et leurs profils de résistance en relation avec les objectifs d'élimination du paludisme. Les données sur la résistance aux insecticides chez An. funestus vecteurs du paludisme en Afrique ont été extraites d'études publiées dans des bases de données bibliographiques comme Google Scholar et PubMed. Les articles publiés entre 2000 et mai 2023, rapportant la résistance de An. funestus aux insecticides et les mécanismes associés ont été inclus. Ceux portant uniquement sur la bionomie ont été exclus. Au total 174 articles portant sur la variation spatiale de la résistance des espèces du groupe An. funestus aux insecticides répondaient aux critères de sélection. De ces analyses, il ressort qu'An. funestus était de plus en plus résistant aux quatre classes d'insecticides recommandées par l'Organisation Mondiale de la Santé (OMS) pour le contrôle des vecteurs du paludisme ce qui semble réduire l'efficacité des méthodes de contrôle des vecteurs, en particulier les moustiquaires imprégnées d'insecticide et la pulvérisation intradomiciliaire. avec des variations en fonction des pays. Les mécanismes de résistance aux insecticides de type biochimique liée aux enzymes de détoxification (P450S et GST) ont été largement rapportés chez An. funestus. De nombreux gènes P450 associés à la résistance métabolique ont été mis en évidence chez An. funestus collecté sur le terrain. Cependant, An. funestus en Afrique reste sensible à d'autres classes d'insecticides, telles que les organophosphorés et les néonicotinoïdes. La résistance aux insecticides. Cette revue met en évidence la résistance croissante aux insecticides chez les moustiques du groupe Funestus, un vecteur important du paludisme en Afrique, posant ainsi un défi important aux efforts de contrôle du paludisme. Tandis que An. funestus a montré une résistance aux classes d'insecticide recommandées, notamment les pyréthroïdes et, dans certains cas, les organochlorés et les carbamates, il reste sensible à d'autres classes d'insecticides tels que les organophosphorés et les néonicotinoïdes, offrant des options alternatives potentielles de contrôle des vecteurs. L'étude souligne la nécessité d'interventions ciblées qui considèrent la structure de la population et la distribution géographique d'An. funestus, y compris ses sous espèces et leurs profils de résistance aux insecticides, pour atteindre efficacement les objectifs d'élimination du paludisme.


Assuntos
Anopheles , Resistência a Inseticidas , Inseticidas , Malária , Mosquitos Vetores , Animais , Resistência a Inseticidas/genética , Anopheles/efeitos dos fármacos , Anopheles/genética , Mosquitos Vetores/efeitos dos fármacos , Mosquitos Vetores/genética , África , Malária/transmissão , Malária/prevenção & controle , Inseticidas/farmacologia , Distribuição Animal
15.
PLoS One ; 19(2): e0294192, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-38354118

RESUMO

BACKGROUND: Surveillance of malaria vectors is crucial for assessing the transmission risk and impact of control measures. Human landing catches (HLC) directly estimate the biting rates but raise ethical concerns due to the exposure of volunteers to mosquito-borne pathogens. A common alternative is the CDC-light trap, which is effective for catching host-seeking mosquitoes indoors but not outdoors. New, exposure-free methods are needed for sampling mosquitoes indoors and outdoors in ways that reflect their natural risk profiles. The aim of this study was therefore to evaluate the efficacy of the miniaturized double net trap (DN-Mini) for sampling host-seeking mosquitoes in south-eastern Tanzania, where malaria transmission is dominated by Anopheles funestus. METHODS: Adult mosquitoes were collected from 222 randomly selected houses across three villages (74 per village) in Ulanga district, south-eastern Tanzania, using the DN-Mini traps, CDC-Light traps, and Prokopack aspirators. First, we compared CDC-light and DN-Mini traps for collecting indoor host-seeking mosquitoes, while Prokopack aspirators were used for indoor-resting mosquitoes. Second, we deployed the DN-Mini and Prokopack aspirators to collect host-seeking and resting mosquitoes indoors and outdoors. Generalized linear mixed models (GLMM) with a negative binomial distribution were used to compare the effectiveness of the traps for catching different mosquito species. RESULTS: The DN-Mini was 1.53 times more efficient in collecting An. funestus indoors (RR = 1.53, 95% CI: 1.190-1.98) compared to the CDC-Light trap. However, for Anopheles arabiensis, the DN-Mini caught only 0.32 times as many mosquitoes indoors as the CDC-Light traps (RR = 0.32, 95% CI: 0.183-0.567). Both An. funestus and An. arabiensis were found to be more abundant indoors than outdoors when collected using the DN-Mini trap. Similarly, the Prokopack aspirator was greater indoors than outdoors for both An. funestus and An. arabiensis. CONCLUSION: The DN-Mini outperformed the CDC-light trap in sampling the dominant malaria vector, An. funestus species, but was less effective in capturing An. arabiensis, and for both vector species, the biting risk was greater indoors than outdoors when measured using the DN-Mini trap. These findings highlight the importance of selecting appropriate trapping methods based on mosquito species and behaviors.


Assuntos
Anopheles , Malária , Adulto , Animais , Humanos , Malária/epidemiologia , Tanzânia/epidemiologia , Entomologia/métodos , Mosquitos Vetores , Ligante de CD40 , Controle de Mosquitos/métodos
16.
Acta Trop ; 251: 107104, 2024 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-38185187

RESUMO

Disease surveillance, including entomological surveillance, serves as the basis for all vector control program activities. How to do this in the most ecologically sensible way, so that the most suitable, naturalistic method, of control for that population can be identified, should be a priority. Here we describe a set of techniques, whose only energy requirement is a torch (flashlight), that can be used to collect both endo and exophagic and endo and exophilic malaria vectors. The data obtained over a number of years from an individual sentinel house in a village in Mozambique and from a village in Cambodia using these kinds of collection techniques, is presented.


Assuntos
Anopheles , Malária , Animais , Humanos , Malária/epidemiologia , Malária/prevenção & controle , Insetos Vetores , Mosquitos Vetores , África/epidemiologia , Controle de Mosquitos/métodos
17.
Sci Rep ; 14(1): 1002, 2024 01 10.
Artigo em Inglês | MEDLINE | ID: mdl-38200070

RESUMO

Effective larviciding for malaria control requires detailed studies of larvicide efficacies, aquatic habitat characteristics, and life history traits of target vectors. Mosquitoes with brief larval phases present narrower timeframes for biolarvicidal effects than mosquitoes with extended periods. We evaluated two biolarvicides, VectoBac (Bacillus thuringiensis israelensis (Bti)) and VectoMax (Bti and Bacillus sphaericus) against Anopheles funestus and Anopheles arabiensis in shaded and unshaded habitats; and explored how larval development might influence retreatment intervals. These tests were done in semi-natural habitats using field-collected larvae, with untreated habitats as controls. Additionally, larval development was assessed in semi-natural and natural habitats in rural Tanzania, by sampling daily and recording larval developmental stages. Both biolarvicides reduced larval densities of both species by >98% within 72 h. Efficacy lasted one week in sun-exposed habitats but remained >50% for two weeks in shaded habitats. An. funestus spent up to two weeks before pupating (13.2(10.4-16.0) days in semi-natural; 10.0(6.6-13.5) in natural habitats), while An. arabiensis required slightly over one week (8.2 (5.8-10.6) days in semi-natural; 8.3 (5.0-11.6) in natural habitats). The findings suggest that weekly larviciding, which is essential for An. arabiensis might be more effective for An. funestus whose prolonged aquatic growth allows for repeated exposures. Additionally, the longer residual effect of biolarvicides in shaded habitats indicates they may require less frequent treatments compared to sun-exposed areas.


Assuntos
Anopheles , Bacillus thuringiensis , Malária , Animais , Larva , Malária/prevenção & controle , Mosquitos Vetores , Retratamento
18.
Parasit Vectors ; 17(1): 26, 2024 Jan 21.
Artigo em Inglês | MEDLINE | ID: mdl-38246994

RESUMO

BACKGROUND: Sugar-feeding behaviour is essential for mosquito survival and reproduction, and has been exploited to develop new control strategies, such as the attractive targeted sugar baits (ATSB). This study examined the sugar-feeding habits of the dengue vector, Aedes aegypti, in semi-field conditions to determine the optimal timing (age) of sugar meals and whether the availability of sugar sources could affect blood-feeding by these mosquitoes. METHODS: A series of paired-choice assays were conducted in which mosquitoes were allowed to choose between a sugar meal or a blood meal directly from a rabbit. Female 1-day-old mosquitoes were given meal choices in cages I-V and observed for feeding choice in only one cage every day for 5 days starting with cages I to V. The preference of Ae. aegypti to feed on sugar or blood and the effect of sugar source availability on blood-feeding was assessed at different chronological and physiological ages. RESULTS: In the first 5 days post-emergence, there was no significant difference in mosquito preference for sugar or blood meals. However, after the first gonotrophic cycle, they had a greater preference for blood over sugar (odds ratio, OR [95% confidence interval, CI] = 9.4 [6.7-13.0]; P < 0.001). Nulliparous Ae. aegypti females (≤ 5-day-old mosquitoes) were less likely to blood-feed if both sugar and blood sources were concurrently available (OR = 0.06 [0.02-0.16]; P < 0.001). CONCLUSIONS: Newly emerged females of Ae. aegypti mosquitoes were equally likely to choose a sugar meal or a blood meal. However, after the first gonotrophic cycle, they had a greater preference for blood over sugar. Additionally, nulliparous female mosquitoes were less likely to blood-feed when both sugar and blood sources were available. These findings provide insights into the sugar-feeding behaviour of Ae. aegypti and can inform the development and optimization of new control strategies such as using ATSB.


Assuntos
Aedes , Dengue , Feminino , Animais , Açúcares , Mosquitos Vetores , Bioensaio , Dengue/prevenção & controle
19.
Parasit Vectors ; 17(1): 38, 2024 Jan 29.
Artigo em Inglês | MEDLINE | ID: mdl-38287419

RESUMO

BACKGROUND: Anopheles funestus is a major malaria vector in Eastern and Southern Africa and is currently the dominant malaria-transmitting vector in many parts of Tanzania. Previous research has identified its preference for specific aquatic habitats, especially those that persist in dry months. This observation suggests the potential for targeted control through precise habitat mapping and characterization. In this study, we investigated the influence of habitat characteristics, land cover and human population densities on An. funestus distribution during dry seasons. Based on the results, we developed a habitat suitability model for this vector species in south-eastern Tanzania. METHODS: Eighteen villages in south-eastern Tanzania were surveyed during the dry season from September-December 2021. Water bodies were systematically inspected for mosquito larvae and characterized by their physico-chemical characteristics and surrounding environmental features. A generalized linear model was used to assess the presence of An. funestus larvae as a function of the physico-chemical characteristics, land use and human population densities. The results obtained from this model were used to generate spatially explicit predictions of habitat suitability in the study districts. RESULTS: Of the 1466 aquatic habitats surveyed, 440 were positive for An. funestus, with river streams having the highest positivity (74%; n = 322) followed by ground pools (15%; n = 67). The final model had an 83% accuracy in predicting positive An. funestus habitats, with the most important characteristics being permanent waters, clear waters with or without vegetation or movement and shading over the habitats. There was also a positive association of An. funestus presence with forested areas and a negative association with built-up areas. Human population densities had no influence on An. funestus distribution. CONCLUSIONS: The results of this study underscore the crucial role of both the specific habitat characteristics and key environmental factors, notably land cover, in the distribution of An. funestus. In this study area, An. funestus predominantly inhabits river streams and ground pools, with a preference for clear, perennial waters with shading. The strong positive association with more pristine environments with tree covers and the negative association with built-up areas underscore the importance of ecological transitions in vector distribution and malaria transmission risk. Such spatially explicit predictions could enable more precise interventions, particularly larval source management, to accelerate malaria control.


Assuntos
Anopheles , Malária , Humanos , Animais , Estações do Ano , Tanzânia/epidemiologia , Mosquitos Vetores , Ecossistema , Rios , Larva
20.
Malar J ; 22(1): 384, 2023 Dec 21.
Artigo em Inglês | MEDLINE | ID: mdl-38129897

RESUMO

BACKGROUND: Gene drive modified mosquitoes (GDMMs) have the potential to address Africa's persistent malaria problem, but are still in early stages of development and testing. Continuous engagement of African stakeholders is crucial for successful evaluation and implementation of these technologies. The aim of this multi-country study was, therefore, to explore the insights and recommendations of key stakeholders across Africa on the potential of GDMMs for malaria control and elimination in the continent. METHODS: A concurrent mixed-methods study design was used, involving a structured survey administered to 180 stakeholders in 25 countries in sub-Saharan Africa, followed by 18 in-depth discussions with selected groups and individuals. Stakeholders were drawn from academia, research and regulatory institutions, government ministries of health and environment, media and advocacy groups. Thematic content analysis was used to identify key topics from the in-depth discussions, and descriptive analysis was done to summarize information from the survey data. RESULTS: Despite high levels of awareness of GDMMs among the stakeholders (76.7%), there was a relatively low-level of understanding of their key attributes and potential for malaria control (28.3%). When more information about GDMMs was provided to the stakeholders, they readily discussed their insights and concerns, and offered several recommendations to ensure successful research and implementation of the technology. These included: (i) increasing relevant technical expertise within Africa, (ii) generating local evidence on safety, applicability, and effectiveness of GDMMs, and (iii) developing country-specific regulations for safe and effective governance of GDMMs. A majority of the respondents (92.9%) stated that they would support field trials or implementation of GDMMs in their respective countries. This study also identified significant misconceptions regarding the phase of GDMM testing in Africa, as several participants incorrectly asserted that GDMMs were already present in Africa, either within laboratories or released into the field. CONCLUSION: Incorporating views and recommendations of African stakeholders in the ongoing research and development of GDMMs is crucial for instilling stakeholder confidence on their potential application. These findings will enable improved planning for GDMMs in Africa as well as improved target product profiles for the technologies to maximize their potential for solving Africa's enduring malaria challenge.


Assuntos
Culicidae , Tecnologia de Impulso Genético , Malária , Animais , Humanos , Tecnologia de Impulso Genético/métodos , África Subsaariana , Governo , Malária/prevenção & controle
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...