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1.
Rev Prat ; 70(3): 318-325, 2020 Mar.
Artigo em Francês | MEDLINE | ID: mdl-32877069

RESUMO

Dengue fever: an emerging infectious disease. Dengue fever is caused by an arbovirus of the family Flaviviridae and the genus Flavivirus, of which there are 4 serotypes (DEN-1, DEN-2, DEN-3, DEN-4). It is transmitted by the bite of a diurnal mosquito of the genus Aedes, mainly A. aegypti and A. albopictus. An increasing cause of acute fever in travellers, it threatens to emerge in temperate regions where competent mosquitoes (Aedes) are established. Dengue fever is characterized by its clinical polymorphism ranging from asymptomatic to severe forms, which are rare in travellers. Its definite diagnosis is based on virological tests selected according to the stage of the disease and the kinetics of the virus. Its treatment is only symptomatic. It is a notifiable disease in mainland France and is subject to a plan to combat its spread and to specific surveillance in the overseas departments. Dengue prevention is based on the application of personal anti-vectorial protection measures among travellers, awareness-raising among health professionals and social mobilization to combat larval gites in endemic regions or regions colonized by Aedes. In France, the tetravalent vaccine Dengvaxia, which is licensed in France, is not recommended for people residing in overseas departments and for travelers to endemic areas.


Assuntos
Aedes , Doenças Transmissíveis Emergentes , Vírus da Dengue , Dengue , Animais , Dengue/epidemiologia , Dengue/transmissão , França/epidemiologia , Medicina de Viagem
2.
PLoS Negl Trop Dis ; 14(8): e0008605, 2020 08.
Artigo em Inglês | MEDLINE | ID: mdl-32797109

RESUMO

In human communities inhabiting areas-such as West Bengal- India-where perpetuate the pre-imago & adult developmental stages of mosquitoes; many infectious diseases are still diagnosed such as Dengue, Malaria and Acute Encephalitis Syndrome. The control of the aquatic developmental stages is one of the easiest way to prevent the emergence of adults-the blood feeding adult females being thus prevented to sample their blood meal and to lay their eggs in the aquatic milieu where develop the aquatic pre-imaginal developmental stages. Moreover, reducing the adult population size also the probability of for the blood feeding adult female mosquitoes to act as hosts and vectors of the arboviruses such as dengue virus & Japanese encephalitis virus as well as of Plasmodium. Several environmental factors including water quality parameters are responsible for the selection of oviposition sites by the female mosquitoes. In our study, larval densities of three important mosquitoes (Aedes/A. albopictus, Anopheles/An. stephensi and Culex/C. vishnui) were measured and water qualities of their habitat i.e. pH, Specific Conductance, Dissolved Oxygen, Chemical Oxygen Demand, Total alkalinity (Talk), Hardness, Nitrate nitrogen and Ammonia nitrogen were analyzed in 2017 and 2018 in many districts of West Bengal where humans beings are suffering from arboviruses and /or malaria. Whereas we have found positive correlation of density of C. vishnui and A. albopictus with the water factors except Chemical Oxygen Demand (COD) and Talk, for An. stephensi all these factors except pH, COD and Talk have positive correlation. Hardness of the water shows positive correlation with the density of An. stephensi and C. vishnui but negative correlation with density of A. albopictus. Contour plot analysis demonstrates that occurrence of each mosquito species lies in between specific range of water factors. Inter- correlation analysis revealed that mosquitoes were negatively correlated with each other. A positive correlation of the water quality parameters and larval density, over two successive years, was also noticed. In conclusion, the increasing level of pollution due to industrial and other irresponsible waste management system which changes the water quality parameters may also influence mosquito population.


Assuntos
Ecossistema , Controle de Mosquitos , Mosquitos Vetores/fisiologia , Aedes/fisiologia , Animais , Anopheles/fisiologia , Arbovirus , Culex/fisiologia , Dengue/transmissão , Vírus da Encefalite Japonesa (Espécie) , Encefalite Japonesa/transmissão , Feminino , Humanos , Concentração de Íons de Hidrogênio , Índia , Larva , Modelos Logísticos , Malária/transmissão , Mosquitos Vetores/parasitologia , Mosquitos Vetores/virologia , Análise Multivariada , Densidade Demográfica , Água
4.
PLoS Pathog ; 16(7): e1008410, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-32726353

RESUMO

The bacterial endosymbiont Wolbachia is a biocontrol tool that inhibits the ability of the Aedes aegypti mosquito to transmit positive-sense RNA viruses such as dengue and Zika. Growing evidence indicates that when Wolbachia strains wMel or wAlbB are introduced into local mosquito populations, human dengue incidence is reduced. Despite the success of this novel intervention, we still do not fully understand how Wolbachia protects mosquitoes from viral infection. Here, we demonstrate that the Wolbachia strain wPip does not inhibit virus infection in Ae. aegypti. We have leveraged this novel finding, and a panel of Ae. aegypti lines carrying virus-inhibitory (wMel and wAlbB) and non-inhibitory (wPip) strains in a common genetic background, to rigorously test a number of hypotheses about the mechanism of Wolbachia-mediated virus inhibition. We demonstrate that, contrary to previous suggestions, there is no association between a strain's ability to inhibit dengue infection in the mosquito and either its typical density in the midgut or salivary glands, or the degree to which it elevates innate immune response pathways in the mosquito. These findings, and the experimental platform provided by this panel of genetically comparable mosquito lines, clear the way for future investigations to define how Wolbachia prevents Ae. aegypti from transmitting viruses.


Assuntos
Aedes/microbiologia , Vírus da Dengue , Interações Microbianas/fisiologia , Mosquitos Vetores/microbiologia , Wolbachia , Animais , Dengue/prevenção & controle , Dengue/transmissão , Infecções por Bactérias Gram-Negativas , Controle Biológico de Vetores/métodos , Fenótipo
5.
PLoS One ; 15(7): e0234959, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32663230

RESUMO

The economic and social impacts due to diseases transmitted by mosquitoes in the latest years have been significant. Currently, no specific treatment or commercial vaccine exists for the control and prevention of arboviruses, thereby making entomological characterization fundamental in combating diseases such as dengue, chikungunya, and Zika. The morphological identification of mosquitos includes a visual exam of the samples. It is time consuming and requires adequately trained professionals. Accordingly, the development of a new automated method for realizing mosquito-perception and -classification is becoming increasingly essential. Therefore, in this study, a computational model based on a convolutional neural network (CNN) was developed to extract features from the images of mosquitoes and then classify the species Aedes aegypti, Aedes albopictus, and Culex quinquefasciatus. In addition, the model was trained to detect the mosquitoes of the genus Aedes. To train CNNs to perform the automatic morphological classification of mosquitoes, a dataset, which included 7,561 images of the target mosquitoes and 1,187 images of other insects, was acquired. Various neural networks, such as Xception and DenseNet, were used for developing the automatic-classification model based on images. A structured optimization process of random search and grid search was developed to select the hyperparameters set and increase the accuracy of the model. In addition, strategies to eliminate overfitting were implemented to increase the generalization of the model. The optimized model, during the test phase, obtained the balanced accuracy (BA) of 93.5% in classifying the target mosquitoes and other insects and the BA of 97.3% in detecting the mosquitoes of the genus Aedes in comparison to Culex. The results provide fundamental information for performing the automatic morphological classification of mosquito species. Using a CNN-embedded entomological tool is a valuable and accessible resource for health workers and non-taxonomists for identifying insects that can transmit infectious diseases.


Assuntos
Arbovirus/classificação , Culicidae/classificação , Processamento de Imagem Assistida por Computador/métodos , Aedes/virologia , Animais , Automação Laboratorial/métodos , Febre de Chikungunya/transmissão , Vírus Chikungunya/genética , Culex/virologia , Culicidae/genética , Dengue/transmissão , Vírus da Dengue/genética , Feminino , Masculino , Mosquitos Vetores/virologia , Zika virus/genética , Infecção por Zika virus/transmissão
6.
PLoS One ; 15(6): e0233669, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32502226

RESUMO

Only few data exist in Cambodia on mosquito diversity and their potential role as vectors. Many arboviruses, such as dengue and Japanese encephalitis, are endemic and mostly affect children in the country. This research sets out to evaluate vector relative abundance and diversity in primary schools in Cambodia in an attempt to explain the apparent burden of dengue fever, severe dengue (DEN), Japanese encephalitis (JE), other arboviral diseases and malaria among children, 15 years and under, attending selected primary schools through vector surveys. Entomological surveys were implemented in primary schools in two provinces of Cambodia to assess the potential risk of exposure of schoolchildren to mosquito vector species. Light traps and BG traps were used to collect adult mosquitoes in 24 schools during the rainy and dry seasons of 2017 and 2018 in Kampong Cham and Tboung Khmum provinces. A total of 61 species were described, including Aedes, Culex and Anopheles species. The relative abundance and biodiversity of mosquito species were dependent on the month and school. Of the 37,725 mosquitoes caught during the study, three species accounted for three-quarters of the relative abundance: Culex vishnui, Anopheles indefinitus and Culex quinquefasciatus. More importantly, nearly 90% of the mosquitoes caught in the schools were identified as potential vectors of pathogens including Japanese encephalitis, dengue, and malaria parasites. Our results showed that schools in Cambodia represent a risk for vector-borne disease transmission and highlight the importance of implementing vector control in schools in Cambodia to decrease the risk of transmission.


Assuntos
Infecções por Arbovirus/transmissão , Arbovirus/isolamento & purificação , Mosquitos Vetores , Adolescente , Infecções por Arbovirus/epidemiologia , Arbovirus/classificação , Biodiversidade , Camboja/epidemiologia , Criança , Pré-Escolar , Dengue/epidemiologia , Dengue/transmissão , Dengue/virologia , Encefalite Japonesa/epidemiologia , Encefalite Japonesa/transmissão , Encefalite Japonesa/virologia , Humanos , Malária/epidemiologia , Malária/transmissão , Malária/virologia
7.
PLoS Negl Trop Dis ; 14(6): e0008362, 2020 06.
Artigo em Inglês | MEDLINE | ID: mdl-32559197

RESUMO

Arboviruses are among the most important emerging pathogens due to their increasing public health impact. In Kenya, continued population growth and associated urbanization are conducive to vector spread in both urban and rural environments, yet mechanisms of viral amplification in vector populations is often overlooked when assessing risks for outbreaks. Thus, the characterization of local arbovirus circulation in mosquito populations is imperative to better inform risk assessments and vector control practices. Aedes species mosquitoes were captured at varying stages of their life cycle during different seasons between January 2014 and May 2016 at four distinct sites in Kenya, and tested for chikungunya (CHIKV), dengue (DENV) and Zika (ZIKV) viruses by RT-PCR. CHIKV was detected in 45 (5.9%) and DENV in 3 (0.4%) mosquito pools. No ZIKV was detected. Significant regional variation in prevalence was observed, with greater frequency of CHIKV on the coast. DENV was detected exclusively on the coast. Both viruses were detected in immature mosquitoes of both sexes, providing evidence of transovarial transmission of these arboviruses in local mosquitoes. This phenomenon may be driving underlying viral maintenance that may largely contribute to periodic re-emergence among humans in Kenya.


Assuntos
Febre de Chikungunya/transmissão , Vírus Chikungunya/isolamento & purificação , Culicidae/virologia , Vírus da Dengue/isolamento & purificação , Dengue/transmissão , Aedes/fisiologia , Aedes/virologia , Animais , Arbovirus , Febre de Chikungunya/epidemiologia , Febre de Chikungunya/virologia , Culicidae/fisiologia , Dengue/epidemiologia , Dengue/virologia , Feminino , Humanos , Quênia/epidemiologia , Estágios do Ciclo de Vida , Masculino , Zika virus , Infecção por Zika virus/virologia
8.
Environ Sci Pollut Res Int ; 27(25): 31863-31871, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32504436

RESUMO

The Aedes albopictus mosquito is a vector of several deadly diseases of humans and domesticated animals. Usually, synthetic insecticides are used for mosquito control. The excessive use of synthetic insecticides is hazardous for humans and the environment. Therefore, there is a need to develop environment-friendly and novel mosquito larvicides. In the current study, we evaluated larvicidal and bite protection properties of Seriphidium brevifolium essential oil (SBEO) and its active constituents against this mosquito. SBEO and its active constituents, α, ß-thujone, and limonene, were toxic to A. albopictus, with LC50 values of 21.43, 45.99, 47.38, and 49.46 µg/mL. The cream formulation of EO at 5 % (w/v) provided complete protection against mosquito bites until 70 min after application. Among the EO constituents tested, α and ß-thujone showed considerable protections against mosquito bites but lower as compared with the whole oil. Furthermore, 1:1 combinations of active constituent α-thujone and ß-thujone and 1:1:1 combinations of α-thujone, ß-thujone, and limonene displayed a synergistic effect against the larvae. Particularly, the EO and its active constituents were safer to Poecilia reticulata a mosquito predator, with LC50 ranging from 3934.33 to 14,432.11 µg/mL. Our current study indicated that SBEO and some of its constituents can be used for the control of A. albopictus mosquito, as a novel alternative to hazardous synthetic insecticides and to overcome the problem of increasing insecticides resistance.


Assuntos
Aedes , Anopheles , Culex , Dengue/transmissão , Inseticidas , Óleos Voláteis , Animais , Humanos , Larva , Controle de Mosquitos , Mosquitos Vetores , Folhas de Planta
10.
PLoS One ; 15(5): e0233618, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32469954

RESUMO

A simple device using folded Parafilm-M as an artificial blood feeder was designed for studying two important dengue vector mosquitoes, Aedes aegypti and Aedes albopictus. The efficiency of the artificial blood feeder was investigated by comparing the numbers of engorged mosquitoes that fed on the artificial blood feeder versus mice as a live blood source. Significantly more engorged females Aedes aegypti fed on the artificial blood feeder than on mice. In addition, the artificial feeder could serve as a useful apparatus for oral infection via artificial blood meals, and for saliva collection in mosquitoes. Our method enabled us to collect saliva from multiple mosquitoes at once, providing sufficient infected saliva for determination of the virus titer by plaque assay analysis. Our artificial feeder has the advantage that it is simple, inexpensive, and efficient.


Assuntos
Aedes/virologia , Vírus da Dengue/isolamento & purificação , Dengue/transmissão , Mosquitos Vetores/virologia , Aedes/fisiologia , Ração Animal/análise , Animais , Feminino , Humanos , Camundongos , Mosquitos Vetores/fisiologia , Saliva/virologia
11.
Am J Trop Med Hyg ; 103(1): 112-119, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-32431270

RESUMO

This study describes the natural history of dengue virus (DENV) infection in rhesus monkeys exposed to the bites of DENV-infected Aedes aegypti mosquitoes. Dengue virus-infected mosquitoes were generated by either intrathoracic inoculation or by oral feeding on viremic blood meals. Each of the six rhesus monkeys that were fed upon by intrathoracically infected mosquitoes developed non-structural protein 1 (NS1) antigenemia and an IgM response; viremia was detected in 4/6 individuals. No virological or immunological evidence of DENV infection was detected in the three monkeys exposed to mosquitoes that had been orally infected with DENV. These results demonstrate the utility of mosquito-borne challenge of rhesus monkeys with DENV.


Assuntos
Aedes/virologia , Anticorpos Antivirais/sangue , Vírus da Dengue/imunologia , Dengue/imunologia , Imunoglobulina M/sangue , Mosquitos Vetores/virologia , Viremia/imunologia , Animais , Dengue/sangue , Dengue/diagnóstico , Dengue/transmissão , Vírus da Dengue/genética , Ensaio de Imunoadsorção Enzimática , Feminino , Humanos , Macaca mulatta , Projetos Piloto , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Proteínas não Estruturais Virais/genética , Viremia/sangue , Viremia/diagnóstico , Viremia/transmissão
12.
Am J Trop Med Hyg ; 103(1): 445-454, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-32394876

RESUMO

The Aedes aegypti mosquito inhabits most tropical and subtropical regions of the globe, where it transmits arboviral diseases of substantial public health relevance, such as dengue fever. In subtropical regions, Ae. aegypti often presents an annual abundance cycle driven by weather conditions. Because different population states may show varying responses to control, we are interested in studying what time of the year is most appropriate for control. To do so, we developed two dynamic site-occupancy models based on more than 200 weeks of mosquito trapping data from nearly 900 sites in a subtropical Brazilian city. Our phenomenological, Markovian models, fitted to data in a Bayesian framework, accounted for failure to detect mosquitoes in two alternative ways and for temporal variation in dynamic rates of local extinction and colonization of new sites. Infestation varied from nearly full cover of the city area in late summer, to between 10% and 67% of sites occupied in winter depending on the model. Sensitivity analysis reveals that changes in dynamic rates should have the greatest impact on site occupancy during autumn and early winter months, when the mosquito population is declining. We discuss the implications of this finding to the timing of mosquito control.


Assuntos
Aedes , Dengue/transmissão , Controle de Mosquitos/métodos , Estações do Ano , Aedes/virologia , Animais , Teorema de Bayes , Brasil/epidemiologia , Dengue/epidemiologia , Humanos , Cadeias de Markov , Dinâmica Populacional , Fatores de Tempo , Tempo (Meteorologia)
13.
PLoS Negl Trop Dis ; 14(5): e0007504, 2020 05.
Artigo em Inglês | MEDLINE | ID: mdl-32392222

RESUMO

In South East Asia, dengue epidemics have increased in size and geographical distribution in recent years. We examined the spatiotemporal distribution and epidemiological characteristics of reported dengue cases in the predominantly rural state of Sabah, in Malaysian Borneo-an area where sylvatic and urban circulation of pathogens are known to intersect. Using a public health data set of routinely notified dengue cases in Sabah between 2010 and 2016, we described demographic and entomological risk factors, both before and after a 2014 change in the clinical case definition for the disease. Annual dengue incidence rates were spatially variable over the 7-year study period from 2010-2016 (state-wide mean annual incidence of 21 cases/100,000 people; range 5-42/100,000), but were highest in rural localities in the western districts of the state (Kuala Penyu, Nabawan, Tenom and Kota Marudu). Eastern districts exhibited lower overall dengue rates, although a high proportion of severe (haemorrhagic) dengue cases (44%) were focused in Sandakan and Tawau. Dengue incidence was highest for those aged between 10 and 29 years (24/100,000), and was slightly higher for males compared to females. Available vector surveillance data indicated that during large outbreaks in 2015 and 2016 the mosquito Aedes albopictus was more prevalent in both urban and rural households (House Index of 64%) than Ae. aegypti (15%). Demographic patterns remained unchanged both before and after the dengue case definition was changed; however, in the years following the change, reported case numbers increased substantially. Overall, these findings suggest that dengue outbreaks in Sabah are increasing in both urban and rural settings. Future studies to better understand the drivers of risk in specific age groups, genders and geographic locations, and to test the potential role of Ae. albopictus in transmission, may help target dengue prevention and control efforts.


Assuntos
Dengue/epidemiologia , Adolescente , Adulto , Aedes/fisiologia , Aedes/virologia , Distribuição por Idade , Animais , Criança , Pré-Escolar , Dengue/mortalidade , Dengue/transmissão , Dengue/virologia , Vírus da Dengue/fisiologia , Feminino , Humanos , Incidência , Lactente , Malásia/epidemiologia , Masculino , Pessoa de Meia-Idade , Mosquitos Vetores/fisiologia , Mosquitos Vetores/virologia , Adulto Jovem
14.
PLoS Negl Trop Dis ; 14(5): e0008320, 2020 05.
Artigo em Inglês | MEDLINE | ID: mdl-32392224

RESUMO

BACKGROUND: The global spread of Aedes albopictus has exposed new geographical areas to the risk of dengue and chikungunya virus transmission. Several autochthonous transmission events have occurred in recent decades in Southern Europe and many indicators suggest that it will become more frequent in this region in the future. Environmental, socioeconomic and climatic factors are generally considered to trigger the emergence of these viruses. Accordingly, a greater knowledge of the determinants of this emergence in a European context is necessary to develop adapted surveillance and control strategies, and public health interventions. METHODOLOGY/PRINCIPAL FINDINGS: Using French surveillance data collected from between 2010 and 2018 in areas of Southern France where Ae. albopictus is already established, we assessed factors associated with the autochthonous transmission of dengue and chikungunya. Cases leading to autochthonous transmission were compared with those without subsequent transmission using binomial regression. We identified a long reporting delay (≥ 21 days) of imported cases to local health authorities as the main driver for autochthonous transmission of dengue and chikungunya in Southern France. The presence of wooded areas around the cases' place of residence and the accumulation of heat during the season also increased the risk of autochthonous arbovirus transmission. CONCLUSIONS: Our findings could inform policy-makers when developing strategies to the emerging threats of dengue and chikungunya in Southern Europe and can be extrapolated in this area to other viruses such as Zika and yellow fever, which share the same vector. Furthermore, our results allow a more accurate characterization of the environments most at risk, and highlight the importance of implementing surveillance systems which ensure the timely reporting and of imported cases and swift interventions.


Assuntos
Aedes/crescimento & desenvolvimento , Febre de Chikungunya/transmissão , Dengue/transmissão , Transmissão de Doença Infecciosa , Mosquitos Vetores/crescimento & desenvolvimento , Animais , Febre de Chikungunya/epidemiologia , Dengue/epidemiologia , Feminino , França/epidemiologia , Humanos , Masculino
15.
PLoS Negl Trop Dis ; 14(5): e0008303, 2020 05.
Artigo em Inglês | MEDLINE | ID: mdl-32407315

RESUMO

In New Caledonia (NC), Aedes aegypti is the only proven vector of dengue virus (DENV), which is the most prevalent arbovirosis in NC. Since World War II, the four DENV serotypes have circulated regularly in NC. The epidemiological profile, however, has evolved over the last ten years, with the persistence of DENV-1 circulation and the co-circulation of several DENV serotypes. The current study evaluated the ability of Ae. aegypti from NC to transmit four DENV serotypes (and two DENV-1 genotypes) isolated during recent outbreaks in NC. An Ae. aegypti F1 generation was twice independently orally challenged with each DENV strain (107 FFU/ml). Infection, dissemination and transmission rates and transmission efficiency were measured at day 7 and 14 post-exposure, as well as the quantity of infectious virus particles. Mosquito infection was observed as early as 7 days post-infection. Infection rates between 18 and 58% were measured for all DENV serotypes/genotypes tested. Although dissemination rates ranged from 78 to 100%, transmission efficiencies were low, with values not exceeding 21% at 14 days post-infection for all DENV strains. This study shows that NC Ae. aegypti are moderately competent for DENV in laboratory conditions. In link with epidemiological data, these results suggest implication of other factors in the sustained circulation of DENV-1 in New Caledonia.


Assuntos
Aedes/virologia , Vírus da Dengue/isolamento & purificação , Dengue/transmissão , Mosquitos Vetores/virologia , Animais , Dengue/epidemiologia , Vírus da Dengue/classificação , Surtos de Doenças , Transmissão de Doença Infecciosa , Feminino , Genótipo , Humanos , Nova Caledônia/epidemiologia , Sorogrupo
16.
PLoS Negl Trop Dis ; 14(4): e0008097, 2020 04.
Artigo em Inglês | MEDLINE | ID: mdl-32275653

RESUMO

Dengue is one of the most important vector-borne diseases, resulting in an estimated hundreds of millions of infections annually throughout the tropics. Control of dengue is heavily dependent upon control of its primary mosquito vector, Aedes aegypti. Innovative interventions that are effective at targeting the adult stage of the mosquito are needed to increase the options for effective control. The use of insecticide-treated curtains (ITCs) has previously been shown to significantly reduce the abundance of Ae. aegypti in and around homes, but the impact of ITCs on dengue virus (DENV) transmission has not been rigorously quantified. A parallel arm cluster-randomized controlled trial was conducted in Iquitos, Peru to quantify the impact of ITCs on DENV seroconversion as measured through plaque-reduction neutralization tests. Seroconversion data showed that individuals living in the clusters that received ITCs were at greater risk to seroconverting to DENV, with an average seroconversion rate of 50.6 per 100 person-years (PY) (CI: 29.9-71.9), while those in the control arm had an average seroconversion rate of 37.4 per 100 PY (CI: 15.2-51.7). ITCs lost their insecticidal efficacy within 6 months of deployment, necessitating re-treatment with insecticide. Entomological indicators did not show statistically significant differences between ITC and non-ITC clusters. It's unclear how the lack of protective efficacy reported here is attributable to simple failure of the intervention to protect against Ae. aegypti bites, or the presence of a faulty intervention during much of the follow-up period. The higher risk of dengue seroconversion that was detected in the ITC clusters may have arisen due to a false sense of security that inadvertently led to less routine protective behaviors on the part of households that received the ITCs. Our study provides important lessons learned for conducting cluster randomized trials for vector control interventions against Aedes-transmitted virus infections.


Assuntos
Dengue/prevenção & controle , Dengue/transmissão , Transmissão de Doença Infecciosa/prevenção & controle , Mosquiteiros Tratados com Inseticida , Controle de Mosquitos/métodos , Adolescente , Adulto , Anticorpos Neutralizantes/sangue , Anticorpos Antivirais/sangue , Criança , Pré-Escolar , Vírus da Dengue/imunologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Testes de Neutralização , Peru , Soroconversão , Resultado do Tratamento , Adulto Jovem
17.
PLoS Comput Biol ; 16(4): e1007743, 2020 04.
Artigo em Inglês | MEDLINE | ID: mdl-32310958

RESUMO

Recent years have seen rising incidence of dengue and large outbreaks of Zika and chikungunya, which are all caused by viruses transmitted by Aedes aegypti mosquitoes. In most settings, the primary intervention against Aedes-transmitted viruses is vector control, such as indoor, ultra-low volume (ULV) spraying. Targeted indoor residual spraying (TIRS) has the potential to more effectively impact Aedes-borne diseases, but its implementation requires careful planning and evaluation. The optimal time to deploy these interventions and their relative epidemiological effects are, however, not well understood. We used an agent-based model of dengue virus transmission calibrated to data from Iquitos, Peru to assess the epidemiological effects of these interventions under differing strategies for deploying them. Specifically, we compared strategies where spray application was initiated when incidence rose above a threshold based on incidence in recent years to strategies where spraying occurred at the same time(s) each year. In the absence of spraying, the model predicted 361,000 infections [inter-quartile range (IQR): 347,000-383,000] in the period 2000-2010. The ULV strategy with the fewest median infections was spraying twice yearly, in March and October, which led to a median of 172,000 infections [IQR: 158,000-183,000], a 52% reduction from baseline. Compared to spraying once yearly in September, the best threshold-based strategy utilizing ULV had fewer median infections (254,000 vs. 261,000), but required more spraying (351 vs. 274 days). For TIRS, the best strategy was threshold-based, which led to the fewest infections of all strategies tested (9,900; [IQR: 8,720-11,400], a 94% reduction), and required fewer days spraying than the equivalent ULV strategy (280). Although spraying twice each year is likely to avert the most infections, our results indicate that a threshold-based strategy can become an alternative to better balance the translation of spraying effort into impact, particularly if used with a residual insecticide.


Assuntos
Biologia Computacional/métodos , Dengue/prevenção & controle , Controle de Mosquitos/métodos , Aedes/fisiologia , Animais , Simulação por Computador , Dengue/epidemiologia , Dengue/transmissão , Surtos de Doenças , Humanos , Incidência , Inseticidas , Modelos Teóricos , Mosquitos Vetores , Infecção por Zika virus/epidemiologia , Infecção por Zika virus/prevenção & controle , Infecção por Zika virus/transmissão
18.
PLoS One ; 15(4): e0230910, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32236146

RESUMO

Several sites, Z-7L, Z-5 and Z-14, in Sibu district, Sarawak, Malaysia, experienced intense dengue transmission in 2014 that continued into 2015. A pilot study with Bacillus thuringiensis israelensis (Bti) to control Aedes aegypti (L.) and Ae. albopictus (Skuse) was evaluated in Z-7L, a densely populated site of 12 ha. Bti treatments were conducted weekly from epidemiology week (EW) 24/2015 for 4 weeks, followed by fortnight treatments for 2 months, in addition to the routine control activities. Bti was directly introduced into potable containers and the outdoor artificial and natural containers were treated via a wide area spray application method using a backpack mister. Aedes indices significantly reduced during the treatment and post treatment phases, compared to the control site, Z-5 (p<0.05). A 51 fold reduction in the incidence rate per 100,000 population (IR) was observed, with one case in 25 weeks (EW 29-52). In Z-5 and Z-14, control sites, a 6 fold reduction in the IR was observed from EW 29-52. However, almost every week there were dengue cases in Z-14 and until EW 44 in Z-5. In 2016, dengue cases resurfaced in Z-7L from EW 4. Intensive routine control activities were conducted, but the IR continued to escalate. The wide area Bti spray misting of the outdoor containers was then included from EW 27 on fortnight intervals. A 6 fold reduction in IR was observed in the Bti treatment phase (EW 32-52) with no successive weekly cases after EW 37. However, in the control sites, there were dengue cases throughout the year from EW 1-52, particularly in Z-14. We feel that the wide area Bti spray application method is an integral component in the control program, in conjunction with other control measures carried out, to suppress the vector population in outdoor cryptic containers and to interrupt the disease transmission.


Assuntos
Bacillus thuringiensis , Agentes de Controle Biológico , Dengue , Mosquitos Vetores , Aedes/microbiologia , Aedes/virologia , Animais , Dengue/epidemiologia , Dengue/transmissão , Reservatórios de Doenças/virologia , Vetores de Doenças , Inseticidas , Larva/microbiologia , Larva/virologia , Malásia/epidemiologia , Controle de Mosquitos/métodos , Mosquitos Vetores/microbiologia , Mosquitos Vetores/virologia , Projetos Piloto , Prevalência
19.
Infect Dis Poverty ; 9(1): 37, 2020 Apr 16.
Artigo em Inglês | MEDLINE | ID: mdl-32295629

RESUMO

BACKGROUND: Dengue virus, an Aedes mosquito-borne flavivirus, is associated with close to 400 million reported infections per annum worldwide. Reduction of dengue virus transmission depends entirely on limiting Aedes breeding or preventing adult female contact with humans. Currently, the World Health Organization promotes the strategic approach of integrated vector management in order to optimise resources for mosquito control. MAIN TEXT: Neglected tropical disease researchers focus on geographical zones where the incidence of clinical cases, and prevalence of vectors, are high. In combatting those infectious diseases such as dengue that affect mainly low-income populations in developing regions, a mosquito-centric approach is frequently adopted. This prioritises environmental factors that facilitate or impede the lifecycle progression of the vector. Climatic variables (such as rainfall and wind speed) that impact the vector's lifecycle either causally or by happenstance also affect the human host's 'lifecycle', but in very different ways. The socioeconomic impacts of the same variables that influence vector control impact host vulnerability but at different points in the human lifecycle to those of the vector. Here, we argue that the vulnerability of the vector and that of the host interact in complex and unpredictable ways that are characteristic of (complex and intransigent) 'wicked problems'. Moreover, they are treated by public health programs in ways that may ignore this complexity. This opinion draws on recent evidence showing that the best climate predictors of the scale of dengue outbreaks in Bangladesh cannot be explained through a simple vector-to-host causal model. CONCLUSIONS: In mapping causal pathways for vector-borne diseases this article makes a case to elevate the lifecycle of the human host to a level closer in equivalence to that of the vector. Here, we suggest value may be gained from transferring Rittel and Webber's concept of a wicked (social) problem to dengue, malaria and other mosquito-transmitted public health concerns. This would take a 'problem definition' rather than a 'solution-finding' approach, particularly when considering problems in which climate impacts simultaneously on human and vector vulnerability.


Assuntos
Mosquitos Vetores/crescimento & desenvolvimento , Doenças Transmitidas por Vetores/transmissão , Aedes/crescimento & desenvolvimento , Aedes/virologia , Animais , Bangladesh/epidemiologia , Dengue/transmissão , Dengue/virologia , Vírus da Dengue/fisiologia , Ecossistema , Humanos , Controle de Mosquitos , Mosquitos Vetores/virologia , Saúde Pública , Doenças Transmitidas por Vetores/epidemiologia , Doenças Transmitidas por Vetores/virologia
20.
Am J Trop Med Hyg ; 103(1): 149-156, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-32342853

RESUMO

Dengue fever and other febrile mosquito-borne diseases place considerable health and economic burdens on small island nations in the Caribbean. Here, we used two methods of cluster detection to find potential hotspots of transmission of dengue and chikungunya in Barbados, and to assess the impact of input surveillance data and methodology on observed patterns of risk. Using Moran's I and spatial scan statistics, we analyzed the geospatial and temporal distribution of disease cases and rates across Barbados for dengue fever in 2013-2016, and a chikungunya outbreak in 2014. During years with high numbers of dengue cases, hotspots for cases were found with Moran's I in the south and central regions in 2013 and 2016, respectively. Using smoothed disease rates, clustering was detected in all years for dengue. Hotspots suggesting higher rates were not detected via spatial scan statistics, but coldspots suggesting lower than expected rates of disease activity were found in southwestern Barbados during high case years of dengue. No significant spatiotemporal structure was found in cases during the chikungunya outbreak. Spatial analysis of surveillance data is useful in identifying outbreak hotspots, potentially complementing existing early warning systems. We caution that these methods should be used in a manner appropriate to available data and reflecting explicit public health goals-managing for overall case numbers or targeting anomalous rates for further investigation.


Assuntos
Febre de Chikungunya/epidemiologia , Vírus Chikungunya/patogenicidade , Vírus da Dengue/patogenicidade , Dengue/epidemiologia , Surtos de Doenças , Análise Espaço-Temporal , Aedes/virologia , Animais , Barbados/epidemiologia , Febre de Chikungunya/transmissão , Febre de Chikungunya/virologia , Vírus Chikungunya/fisiologia , Análise por Conglomerados , Dengue/transmissão , Dengue/virologia , Vírus da Dengue/fisiologia , Doenças Endêmicas/estatística & dados numéricos , Monitoramento Epidemiológico , Humanos , Incidência , Mosquitos Vetores/virologia , Saúde Pública , Risco
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