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1.
Pathogens ; 9(10)2020 Oct 21.
Artigo em Inglês | MEDLINE | ID: mdl-33096624

RESUMO

Dynamics of dengue serotype 2 virus isolated from patients with different disease severity, namely flu-like classic dengue fever (DF) and dengue shock syndrome (DSS) were studied in its mosquito vector Aedes aegypti. We compared isolate infectivity and vector competence (VC) among thirty two A. aegypti-viral isolate pairs. Mosquito populations from high dengue incidence area exhibited overall greater VC than those from low dengue incidence area at 58.1% and 52.5%, respectively. On the other hand, the overall infection rates for the isolates ThNR2/772 (DF, 62.3%) and ThNR2/391 (DSS, 60.9%), were significantly higher than those for isolates ThNR2/406 (DF, 55.2%) and ThNR2/479 (DSS, 54.8%). These results suggest that the efficacy of dengue virus circulation was likely to vary according to the combination between the virus strains and origin of the mosquito strains, and this may have epidemiologic implications toward the incidence of flu-like classic dengue fever (DF) and dengue shock syndrome (DSS).

2.
Parasit Vectors ; 12(1): 477, 2019 Oct 14.
Artigo em Inglês | MEDLINE | ID: mdl-31610813

RESUMO

BACKGROUND: The Asian tiger mosquito, Aedes (Stegomyia) albopictus (Skuse) is an important worldwide invasive species and can be a locally important vector of chikungunya, dengue and, potentially, Zika. This species is native to Southeast Asia where populations thrive in both temperate and tropical climates. A better understanding of the population structure of Ae. albopictus in Lao PDR is very important in order to support the implementation of strategies for diseases prevention and vector control. In the present study, we investigated the genetic variability of Ae. albopictus across a north-south transect in Lao PDR. METHODS: We used variability in a 1337-bp fragment of the mitochondrial cytochrome c oxidase subunit 1 gene (cox1), to assess the population structure of Ae. albopictus in Lao PDR. For context, we also examined variability at the same genetic locus in samples of Ae. albopictus from Thailand, China, Taiwan, Japan, Singapore, Italy and the USA. RESULTS: We observed very high levels of genetic polymorphism with 46 novel haplotypes in Ae. albopictus from 9 localities in Lao PDR and Thailand populations. Significant differences were observed between the Luangnamtha population and other locations in Lao PDR. However, we found no evidence of isolation by distance. There was overall little genetic structure indicating ongoing and frequent gene flow among populations or a recent population expansion. Indeed, the neutrality test supported population expansion in Laotian Ae. albopictus and mismatch distribution analyses showed a lack of low frequency alleles, a pattern often seen in bottlenecked populations. When samples from Lao PDR were analyzed together with samples from Thailand, China, Taiwan, Japan, Singapore, Italy and the USA, phylogenetic network and Bayesian cluster analysis showed that most populations from tropical/subtropical regions are more genetically related to each other, than populations from temperate regions. Similarly, most populations from temperate regions are more genetically related to each other, than those from tropical/subtropical regions. CONCLUSIONS: Aedes albopictus in Lao PDR are genetically related to populations from tropical/subtropical regions (i.e. Thailand, Singapore, and California and Texas in the USA). The extensive gene flow among locations in Lao PDR indicates that local control is undermined by repeated introductions from untreated sites.


Assuntos
Aedes/fisiologia , Mosquitos Vetores/fisiologia , Aedes/classificação , Aedes/genética , Aedes/virologia , Algoritmos , Animais , Ásia Sudeste , Teorema de Bayes , Análise por Conglomerados , DNA/química , DNA/isolamento & purificação , Complexo IV da Cadeia de Transporte de Elétrons/genética , Extremo Oriente , Feminino , Variação Genética , Genética Populacional , Haplótipos , Itália , Laos , Mitocôndrias/enzimologia , Controle de Mosquitos , Mosquitos Vetores/classificação , Mosquitos Vetores/genética , Mosquitos Vetores/virologia , Filogenia , Análise de Sequência de DNA , Clima Tropical , Estados Unidos
3.
PLoS Negl Trop Dis ; 13(10): e0007771, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31658265

RESUMO

BACKGROUND: Important arboviral diseases, such as dengue, chikungunya, and Zika virus infections, are transmitted mainly by the Aedes aegypti vector. So far, controlling this vector species with current tools and strategies has not demonstrated sustainable and significant impacts. Our main objective was to evaluate whether open field release of sterile males, produced from combining the sterile insect technique using radiation with the insect incompatible technique through Wolbachia-induced incompatibility (SIT/IIT), could suppress natural populations of Ae. aegypti in semi-rural village settings in Thailand. METHODOLOGY/PRINCIPAL FINDINGS: Irradiated Wolbachia-infected Aedes aegypti males produced by the SIT/IIT approach were completely sterile and were able to compete with the wild fertile ones. Open field release of these sterile males was conducted in an ecologically isolated village in Chachoengsao Province, eastern Thailand. House-to-house visit and media reports resulted in community acceptance and public awareness of the technology. During intervention, approximately 100-200 sterile males were released weekly in each household. After 6 months of sterile male release, a significant reduction (p<0.05) of the mean egg hatch rate (84%) and the mean number of females per household (97.30%) was achieved in the treatment areas when compared to the control ones. CONCLUSIONS/SIGNIFICANCE: Our study represents the first open field release of sterile Ae. aegypti males developed from a combined SIT/IIT approach. Entomological assessment using ovitraps, adult sticky traps, and portable vacuum aspirators confirmed the success in reducing natural populations of Ae. aegypti females in treated areas. Public awareness through media resulted in positive support for practical use of this strategy in wider areas. Further study using a systematic randomized trial is needed to determine whether this approach could have a significant impact on the diseases transmitted by Ae. aegypti vector.


Assuntos
Aedes/fisiologia , Entomologia/métodos , Controle de Mosquitos/métodos , Mosquitos Vetores/fisiologia , População Rural , Aedes/microbiologia , Aedes/efeitos da radiação , Animais , Feminino , Humanos , Infertilidade Masculina , Masculino , Mosquitos Vetores/microbiologia , Mosquitos Vetores/efeitos da radiação , Dinâmica Populacional , Caracteres Sexuais , Tailândia , Wolbachia/genética , Wolbachia/fisiologia
4.
Glob Health Action ; 11(1): 1549930, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30560735

RESUMO

BACKGROUND: Dengue fever persists as a major global disease burden, and may increase as a consequence of climate change. Along with other measures, research actions to improve diagnosis, surveillance, prevention, and predictive models are highly relevant. The European Commission funded the DengueTools consortium to lead a major initiative in these areas, and this review synthesises the outputs and findings of this work conducted from 2011 to 2016. Research areas: DengueTools organised its work into three research areas, namely [1] Early warning and surveillance systems; [2] Strategies to prevent dengue in children; and [3] Predictive models for the global spread of dengue. Research area 1 focused on case-studies undertaken in Sri Lanka, including developing laboratory-based sentinel surveillance, evaluating economic impact, identifying drivers of transmission intensity, evaluating outbreak prediction capacity and developing diagnostic capacity. Research area 2 addressed preventing dengue transmission in school children, with case-studies undertaken in Thailand. Insecticide-treated school uniforms represented an intriguing potential approach, with some encouraging results, but which were overshadowed by a lack of persistence of insecticide on the uniforms with repeated washing. Research area 3 evaluated potential global spread of dengue, particularly into dengue-naïve areas such as Europe. The role of international travel, changing boundaries of vectors, developing models of vectorial capacity under different climate change scenarios and strategies for vector control in outbreaks was all evaluated. CONCLUDING REMARKS: DengueTools was able to make significant advances in methods for understanding and controlling dengue transmission in a range of settings. These will have implications for public health agendas to counteract dengue, including vaccination programmes. OUTLOOK: Towards the end of the DengueTools project, Zika virus emerged as an unexpected epidemic in the central and southern America. Given the similarities between the dengue and Zika viruses, with vectors in common, some of the DengueTools thinking translated readily into the Zika situation.


Assuntos
Dengue/epidemiologia , Dengue/prevenção & controle , Inseticidas/administração & dosagem , Vigilância de Evento Sentinela , Aedes , Animais , Dengue/diagnóstico , Surtos de Doenças , Epidemias , Humanos , Insetos Vetores/virologia , Internacionalidade , Sri Lanka , Tailândia , Viagem
5.
Ecol Evol ; 8(2): 1352-1368, 2018 01.
Artigo em Inglês | MEDLINE | ID: mdl-29375803

RESUMO

Vector-borne diseases are a major health burden, yet factors affecting their spread are only partially understood. For example, microbial symbionts can impact mosquito reproduction, survival, and vectorial capacity, and hence affect disease transmission. Nonetheless, current knowledge of mosquito-associated microbial communities is limited. To characterize the bacterial and eukaryotic microbial communities of multiple vector species collected from different habitat types in disease endemic areas, we employed next-generation 454 pyrosequencing of 16S and 18S rRNA amplicon libraries, also known as metabarcoding. We investigated pooled whole adult mosquitoes of three medically important vectors, Aedes aegypti, Ae. albopictus, and Culex quinquefasciatus, collected from different habitats across central Thailand where we previously characterized mosquito diversity. Our results indicate that diversity within the mosquito microbiota is low, with the majority of microbes assigned to one or a few taxa. Two of the most common eukaryotic and bacterial genera recovered (Ascogregarina and Wolbachia, respectively) are known mosquito endosymbionts with potentially parasitic and long evolutionary relationships with their hosts. Patterns of microbial composition and diversity appeared to differ by both vector species and habitat for a given species, although high variability between samples suggests a strong stochastic element to microbiota assembly. In general, our findings suggest that multiple factors, such as habitat condition and mosquito species identity, may influence overall microbial community composition, and thus provide a basis for further investigations into the interactions between vectors, their microbial communities, and human-impacted landscapes that may ultimately affect vector-borne disease risk.

6.
PLoS Negl Trop Dis ; 11(9): e0005961, 2017 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-28937986

RESUMO

BACKGROUND: Dengue-related illness is a leading cause of hospitalization and death in Thailand and other Southeast Asian countries, imposing a major economic burden on households, health systems, and governments. This study aims to assess the economic impact of hospitalized dengue cases on households in Chachoengsao province in eastern Thailand. METHODS: We conducted a prospective cost-of-illness study of hospitalized pediatric and adult dengue patients at three public hospitals. We examined all hospitalized dengue cases regardless of disease severity. Patients or their legal guardians were interviewed using a standard questionnaire to determine household-level medical and non-medical expenditures and income losses during the illness episode. RESULTS: Between March and September 2015, we recruited a total of 224 hospitalized patients (<5 years, 4%; 5-14 years, 20%, 15-24 years, 36%, 25-34 years, 15%; 35-44 years, 10%; 45+ years, 12%), who were clinically diagnosed with dengue. The total cost of a hospitalized dengue case was higher for adult patients than pediatric patients, and was US$153.6 and US$166.3 for pediatric DF and DHF patients, respectively, and US$171.2 and US$226.1 for adult DF and DHF patients, respectively. The financial burden on households increased with the severity of dengue illness. CONCLUSIONS: Although 74% of the households reported that the patient received free medical care, hospitalized dengue illness cost approximately 19-23% of the monthly household income. These results indicated that dengue imposed a substantial financial burden on households in Thailand where a great majority of the population was covered by the Universal Coverage Scheme for health care.


Assuntos
Efeitos Psicossociais da Doença , Dengue/economia , Características da Família , Hospitalização/economia , Adolescente , Adulto , Criança , Pré-Escolar , Dengue/epidemiologia , Dengue/virologia , Feminino , Gastos em Saúde , Humanos , Renda , Masculino , Pessoa de Meia-Idade , Estudos Prospectivos , População Rural/estatística & dados numéricos , Dengue Grave/economia , Dengue Grave/epidemiologia , Dengue Grave/virologia , Inquéritos e Questionários , Tailândia/epidemiologia , Adulto Jovem
7.
PLoS One ; 12(8): e0180013, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28854207

RESUMO

BACKGROUND: Dengue is a vector-borne disease transmitted by Aedes mosquitoes. It is considered an important public health problem in many countries worldwide. However, only a few studies have been conducted on primates and domestic animals that could potentially be a reservoir of dengue viruses. Since domestic dogs share both habitats and vectors with humans, this study aimed to investigate whether domestic dogs living in different ecological settings in dengue endemic areas in Thailand could be naturally infected with dengue viruses. METHODOLOGY/PRINCIPAL FINDINGS: Serum samples were collected from domestic dogs in three different ecological settings of Thailand: urban dengue endemic areas of Nakhon Sawan Province; rubber plantation areas of Rayong Province; and Koh Chang, an island tourist spot of Trat Province. These samples were screened for dengue viral genome by using semi-nested RT-PCR. Positive samples were then inoculated in mosquito and dog cell lines for virus isolation. Supernatant collected from cell culture was tested for the presence of dengue viral genome by semi-nested RT-PCR, then double-strand DNA products were double-pass custom-sequenced. Partial nucleotide sequences were aligned with the sequences already recorded in GenBank, and a phylogenetic tree was constructed. In the urban setting, 632 domestic dog serum samples were screened for dengue virus genome by RT-PCR, and six samples (0.95%) tested positive for dengue virus. Four out of six dengue viruses from positive samples were successfully isolated. Dengue virus serotype 2 and serotype 3 were found to have circulated in domestic dog populations. One of 153 samples (0.65%) collected from the rubber plantation area showed a PCR-positive result, and dengue serotype 3 was successfully isolated. Partial gene phylogeny revealed that the isolated dengue viruses were closely related to those strains circulating in human populations. None of the 71 samples collected from the island tourist spot showed a positive result. CONCLUSIONS/SIGNIFICANCE: We concluded that domestic dogs can be infected with dengue virus strains circulating in dengue endemic areas. The role of domestic dogs in dengue transmission needs to be further investigated, i.e., whether they are potential reservoirs or incidental hosts of dengue viruses.


Assuntos
Vírus da Dengue/isolamento & purificação , Dengue/veterinária , Doenças do Cão/epidemiologia , Doenças do Cão/virologia , Cães/virologia , Animais , Dengue/sangue , Dengue/epidemiologia , Vírus da Dengue/genética , Doenças do Cão/sangue , Filogenia , Tailândia/epidemiologia
8.
PLoS Negl Trop Dis ; 11(1): e0005197, 2017 01.
Artigo em Inglês | MEDLINE | ID: mdl-28103255

RESUMO

BACKGROUND: Viral diseases transmitted via Aedes mosquitoes are on the rise, such as Zika, dengue, and chikungunya. Novel tools to mitigate Aedes mosquitoes-transmitted diseases are urgently needed. We tested whether commercially insecticide-impregnated school uniforms can reduce dengue incidence in school children. METHODS: We designed a cluster-randomised controlled trial in Thailand. The primary endpoint was laboratory-confirmed dengue infections. Secondary endpoints were school absenteeism; and impregnated uniforms' 1-hour knock-down and 24 hour mosquito mortality as measured by standardised WHOPES bioassay cone tests at baseline and after repeated washing. Furthermore, entomological assessments inside classrooms and in outside areas of schools were conducted. RESULTS: We enrolled 1,811 pupils aged 6-17 from 5 intervention and 5 control schools. Paired serum samples were obtained from 1,655 pupils. In the control schools, 24/641 (3.7%) and in the intervention schools 33/1,014 (3.3%) students had evidence of new dengue infections during one school term (5 months). There was no significant difference in proportions of students having incident dengue infections between the intervention and control schools, with adjustment for clustering by school. WHOPES cone tests showed a 100% knock down and mortality of Aedes aegypti mosquitoes exposed to impregnated clothing at baseline and up to 4 washes, but this efficacy rapidly declined to below 20% after 20 washes, corresponding to a weekly reduction in knock-down and mosquito mortality by 4.7% and 4.4% respectively. Results of the entomological assessments showed that the mean number of Aedes aegypti mosquitoes caught inside the classrooms of the intervention schools was significantly reduced in the month following the introduction of the impregnated uniforms, compared to those collected in classrooms of the control schools (p = 0.04). CONCLUSIONS: Entomological assessments showed that the intervention had some impact on the number of Aedes mosquitoes inside treatment schools immediately after impregnation and before insecticidal activity declined. However, there was no serological evidence of protection against dengue infections over the five months school term, best explained by the rapid washing-out of permethrin after 4 washes. If rapid washing-out of permethrin could be overcome by novel technological approaches, insecticide-treated clothes might become a potentially cost-effective and scalable intervention to protect against diseases transmitted by Aedes mosquitoes such as dengue, Zika, and chikungunya. TRIAL REGISTRATION: ClinicalTrials.gov NCT01563640.


Assuntos
Aedes/efeitos dos fármacos , Febre de Chikungunya/prevenção & controle , Dengue/prevenção & controle , Insetos Vetores/efeitos dos fármacos , Inseticidas/farmacologia , Controle de Mosquitos , Permetrina/farmacologia , Roupa de Proteção , Infecção por Zika virus/prevenção & controle , Adolescente , Aedes/fisiologia , Animais , Febre de Chikungunya/transmissão , Febre de Chikungunya/virologia , Vírus Chikungunya/fisiologia , Criança , Dengue/transmissão , Dengue/virologia , Vírus da Dengue/fisiologia , Feminino , Humanos , Insetos Vetores/fisiologia , Masculino , Controle de Mosquitos/instrumentação , Controle de Mosquitos/métodos , Instituições Acadêmicas , Tailândia , Zika virus/fisiologia , Infecção por Zika virus/transmissão , Infecção por Zika virus/virologia
9.
PLoS One ; 11(9): e0161895, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-27669170

RESUMO

BACKGROUND: Dengue is an important neglected tropical disease, with more than half of the world's population living in dengue endemic areas. Good understanding of dengue transmission sites is a critical factor to implement effective vector control measures. METHODS: A cohort of 1,811 students from 10 schools in rural, semi-rural and semi-urban Thailand participated in this study. Seroconversion data and location of participants' residences and schools were recorded to determine spatial patterns of dengue infections. Blood samples were taken to confirm dengue infections in participants at the beginning and the end of school term. Entomological factors included a survey of adult mosquito density using a portable vacuum aspirator during the school term and a follow up survey of breeding sites of Aedes vectors in schools after the school term. Clustering analyses were performed to detect spatial aggregation of dengue infections among participants. RESULTS: A total of 57 dengue seroconversions were detected among the 1,655 participants who provided paired blood samples. Of the 57 confirmed dengue infections, 23 (40.0%) occurred in students from 6 (6.8%) of the 88 classrooms in 10 schools. Dengue infections did not show significant clustering by residential location in the study area. During the school term, a total of 66 Aedes aegypti mosquitoes were identified from the 278 mosquitoes caught in 50 classrooms of the 10 schools. In a follow-up survey of breeding sites, 484 out of 2,399 water containers surveyed (20.2%) were identified as active mosquito breeding sites. DISCUSSION AND CONCLUSION: Our findings suggest that dengue infections were clustered among schools and among classrooms within schools. The schools studied were found to contain a large number of different types of breeding sites. Aedes vector densities in schools were correlated with dengue infections and breeding sites in those schools. Given that only a small proportion of breeding sites in the schools were subjected to vector control measures (11%), this study emphasizes the urgent need to implement vector control strategies at schools, while maintaining efforts at the household level.

11.
Int J Environ Res Public Health ; 11(10): 10694-709, 2014 Oct 16.
Artigo em Inglês | MEDLINE | ID: mdl-25325356

RESUMO

Dengue and malaria are vector-borne diseases and major public health problems worldwide. Changes in climatic factors influence incidences of these diseases. The objective of this study was to investigate the relationship between vector-borne disease incidences and meteorological data, and hence to predict disease risk in a global outreach tourist setting. The retrospective data of dengue and malaria incidences together with local meteorological factors (temperature, rainfall, humidity) registered from 2001 to 2011 on Koh Chang, Thailand were used in this study. Seasonal distribution of disease incidences and its correlation with local climatic factors were analyzed. Seasonal patterns in disease transmission differed between dengue and malaria. Monthly meteorological data and reported disease incidences showed good predictive ability of disease transmission patterns. These findings provide a rational basis for identifying the predictive ability of local meteorological factors on disease incidence that may be useful for the implementation of disease prevention and vector control programs on the tourism island, where climatic factors fluctuate.


Assuntos
Clima , Dengue/epidemiologia , Incidência , Malária/epidemiologia , Modelos Estatísticos , Animais , Dengue/transmissão , Humanos , Umidade , Insetos Vetores , Malária/transmissão , Chuva , Estudos Retrospectivos , Estações do Ano , Temperatura , Tailândia/epidemiologia
12.
PLoS One ; 9(9): e108017, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-25247556

RESUMO

BACKGROUND: Dengue-related illness is a leading cause of hospitalization and death, particularly among children. Practical, acceptable and affordable measures are urgently needed to protect this age group. Schools where children spend most of their day is proposed as an ideal setting to implement preventive strategies against day-biting Aedes mosquitoes. The use of insecticide-treated school uniforms is a promising strategy currently under investigation. METHODS: Using a decision-analytic model, we evaluated the cost-effectiveness of the use of insecticide-treated school uniforms for prevention of dengue, compared with a "do-nothing" alternative, in schoolchildren from the societal perspective. We explored how the potential economic value of the intervention varied under various scenarios of intervention effectiveness and cost, as well as dengue infection risk in school-aged children, using data specific to Thailand. RESULTS: At an average dengue incidence rate of 5.8% per year in school-aged children, the intervention was cost-effective (ICER≤$16,440) in a variety of scenarios when the intervention cost per child was $5.3 or less and the intervention effectiveness was 50% or higher. In fact, the intervention was cost saving (ICER<0) in all scenarios in which the intervention cost per child was $2.9 or less per year and the intervention effectiveness was 50% or higher. The results suggested that this intervention would be of no interest to Thai policy makers when the intervention cost per child was $10.6 or higher per year regardless of intervention effectiveness (ICER>$16,440). CONCLUSIONS: Our results present the potential economic value of the use of insecticide-treated uniforms for prevention of dengue in schoolchildren in a typical dengue endemic setting and highlight the urgent need for additional research on this intervention.


Assuntos
Dengue/prevenção & controle , Controle de Insetos/economia , Inseticidas/administração & dosagem , Roupa de Proteção/economia , Adolescente , Animais , Criança , Análise Custo-Benefício , Dengue/economia , Dengue/epidemiologia , Humanos , Controle de Insetos/métodos , Inseticidas/economia , Modelos Econômicos , Tailândia/epidemiologia
13.
Glob Health Action ; 7: 24887, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-25183313

RESUMO

BACKGROUND: As current dengue control strategies have been shown to be largely ineffective in reducing dengue in school-aged children, novel approaches towards dengue control need to be studied. Insecticide-impregnated school uniforms represent an innovative approach with the theoretical potential to reduce dengue infections in school children. OBJECTIVES: This study took place in the context of a randomised control trial (RCT) to test the effectiveness of permethrin-impregnated school uniforms (ISUs) for dengue prevention in Chachoengsao Province, Thailand. The objective was to assess the acceptability of ISUs among parents, teachers, and principals of school children involved in the trial. METHODOLOGY: Quantitative and qualitative tools were used in a mixed methods approach. Class-clustered randomised samples of school children enrolled in the RCT were selected and their parents completed 321 self-administered questionnaires. Descriptive statistics and logistic regression were used to analyse the quantitative data. Focus group discussions and individual semi-structured interviews were conducted with parents, teachers, and principals. Qualitative data analysis involved content analysis with coding and thematic development. RESULTS: The knowledge and experience of dengue was substantial. The acceptability of ISUs was high. Parents (87.3%; 95% CI 82.9-90.8) would allow their child to wear an ISU and 59.9% (95% CI 53.7-65.9) of parents would incur additional costs for an ISU over a normal uniform. This was significantly associated with the total monthly income of a household and the educational level of the respondent. Parents (62.5%; 95% CI 56.6-68.1) indicated they would be willing to recommend ISUs to other parents. CONCLUSIONS: Acceptability of the novel tool of ISUs was high as defined by the lack of concern along with the willingness to pay and recommend. Considering issues of effectiveness and scalability, assessing acceptability of ISUs over time is recommended.


Assuntos
Dengue/prevenção & controle , Inseticidas , Permetrina , Roupa de Proteção , Instituições Acadêmicas , Docentes , Conhecimentos, Atitudes e Prática em Saúde , Humanos , Pais/psicologia , Fatores Socioeconômicos , Tailândia
14.
Virology ; 464-465: 312-319, 2014 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-25108381

RESUMO

Arthropod-borne viruses significantly impact human health. They span multiple families, all of which include viruses not known to cause disease. Characterizing these representatives could provide insights into the origins of their disease-causing counterparts. Field-caught Aedes aegypti mosquitoes from Nakhon Nayok, Thailand, underwent metagenomic shotgun sequencing to reveal a Bunyavirus closely related to Phasi Charoen (PhaV) virus, isolated in 2009 from Ae. aegypti near Bangkok. Phylogenetic analysis of this virus suggests it is basal to the Phlebovirus genus thus making it ideally positioned phylogenetically for understanding the evolution of these clinically important viruses. Genomic analysis finds that a gene necessary for virulence in vertebrates, but not essential for viral replication in arthropods, is missing. The sequencing of this phylogenetically-notable and genomically-unique Phlebovirus from wild mosquitoes exemplifies the utility and efficacy of metagenomic shotgun sequencing for virus characterization in arthropod vectors of human diseases.


Assuntos
Aedes/virologia , Genoma Viral , Insetos Vetores/virologia , Orthobunyavirus/genética , Phlebovirus/genética , Animais , Infecções por Bunyaviridae/transmissão , Infecções por Bunyaviridae/virologia , Feminino , Humanos , Metagenômica , Dados de Sequência Molecular , Orthobunyavirus/classificação , Orthobunyavirus/isolamento & purificação , Phlebovirus/classificação , Phlebovirus/isolamento & purificação , Filogenia , Tailândia
15.
Int J Environ Res Public Health ; 11(1): 934-51, 2014 Jan 09.
Artigo em Inglês | MEDLINE | ID: mdl-24413705

RESUMO

Highly pathogenic avian influenza (HPAI) remains of concern as a major potential global threat. This article evaluates and discusses the level of vulnerability of medium and small-scale commercial poultry production systems in Thailand related to avian influenza virus re-emergence. We developed a survey on 173 farms in Nakhon Pathom province to identify the global level of vulnerability of farms, and to determine which type of farms appears to be more vulnerable. We used official regulations (the Good Agricultural Practices and Livestock Farm Standards regulations) as a reference to check whether these regulations are respected. The results show that numerous vulnerability factors subsist and could represent, in case of HPAI re-emergence, a significant risk for a large spread of the disease. Bio-security, farm management and agro-commercial practices are particularly significant on that matter: results show that these practices still need a thorough improvement on a majority of farms. Farms producing eggs (especially duck eggs) are more vulnerable than farms producing meat. Those results are consistent with the type of farms that were mostly affected during the 2004-2008 outbreaks in Thailand.


Assuntos
Criação de Animais Domésticos/legislação & jurisprudência , Doenças Transmissíveis Emergentes/transmissão , Influenza Aviária/transmissão , Aves Domésticas , Animais , Análise Espacial , Tailândia
16.
PLoS Negl Trop Dis ; 7(10): e2507, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-24205420

RESUMO

Recent years have seen the greatest ecological disturbances of our times, with global human expansion, species and habitat loss, climate change, and the emergence of new and previously-known infectious diseases. Biodiversity loss affects infectious disease risk by disrupting normal relationships between hosts and pathogens. Mosquito-borne pathogens respond to changing dynamics on multiple transmission levels and appear to increase in disturbed systems, yet current knowledge of mosquito diversity and the relative abundance of vectors as a function of habitat change is limited. We characterize mosquito communities across habitats with differing levels of anthropogenic ecological disturbance in central Thailand. During the 2008 rainy season, adult mosquito collections from 24 sites, representing 6 habitat types ranging from forest to urban, yielded 62,126 intact female mosquitoes (83,325 total mosquitoes) that were assigned to 109 taxa. Female mosquito abundance was highest in rice fields and lowest in forests. Diversity indices and rarefied species richness estimates indicate the mosquito fauna was more diverse in rural and less diverse in rice field habitats, while extrapolated estimates of true richness (Chao1 and ACE) indicated higher diversity in the forest and fragmented forest habitats and lower diversity in the urban. Culex sp. (Vishnui subgroup) was the most common taxon found overall and the most frequent in fragmented forest, rice field, rural, and suburban habitats. The distributions of species of medical importance differed significantly across habitat types and were always lowest in the intact, forest habitat. The relative abundance of key vector species, Aedes aegypti and Culex quinquefasciatus, was negatively correlated with diversity, suggesting that direct species interactions and/or habitat-mediated factors differentially affecting invasive disease vectors may be important mechanisms linking biodiversity loss to human health. Our results are an important first step for understanding the dynamics of mosquito vector distributions under changing environmental features across landscapes of Thailand.


Assuntos
Biodiversidade , Culicidae/classificação , Culicidae/crescimento & desenvolvimento , Ecossistema , Insetos Vetores , Animais , Dengue/epidemiologia , Encefalite por Arbovirus/epidemiologia , Doenças Endêmicas , Feminino , Humanos , Masculino , Tailândia/epidemiologia
17.
Glob Health Action ; 6: 20473, 2013 Mar 28.
Artigo em Inglês | MEDLINE | ID: mdl-23541045

RESUMO

BACKGROUND: Children carry the main burden of morbidity and mortality caused by dengue. Children spend a considerable amount of their day at school; hence strategies that reduce human-mosquito contact to protect against the day-biting habits of Aedes mosquitoes at schools, such as insecticide-impregnated uniforms, could be an effective prevention strategy. METHODOLOGY: We used mathematical models to calculate the risk of dengue infection based on force of infection taking into account the estimated proportion of mosquito bites that occur in school and the proportion of school time that children wear the impregnated uniforms. PRINCIPAL FINDINGS: The use of insecticide-impregnated uniforms has efficacy varying from around 6% in the most pessimistic estimations, to 55% in the most optimistic scenarios simulated. CONCLUSIONS: Reducing contact between mosquito bites and human hosts via insecticide-treated uniforms during school time is theoretically effective in reducing dengue incidence and may be a valuable additional tool for dengue control in school-aged children. The efficacy of this strategy, however, is dependent on the compliance of the target population in terms of proper and consistent wearing of uniforms and, perhaps more importantly, the proportion of bites inflicted by the Aedes population during school time.


Assuntos
Vestuário , Dengue/prevenção & controle , Mordeduras e Picadas de Insetos/prevenção & controle , Inseticidas/administração & dosagem , Inseticidas/farmacologia , Aedes , Animais , Humanos , Incidência , Insetos Vetores , Modelos Teóricos , Roupa de Proteção , Tailândia/epidemiologia
18.
PLoS Negl Trop Dis ; 7(1): e1913, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-23326609

RESUMO

BACKGROUND: The genetic population structure of Aedes (Stegomyia) aegypti (L.), the main vector of dengue virus, is being investigated in areas where a novel dengue suppression program is to be implemented. The aim of the program is to release and establish mosquito populations with impaired virus transmission capabilities. To model effects of the release and devise protocols for its implementation, information about the genetic structure of populations at a range of spatial scales is required. METHODOLOGY/PRINCIPAL FINDINGS: This study investigates a potential release site in the Hua Sam Rong Subdistrict of Plaeng Yao District, Chachoengsao Province, in eastern Thailand which comprises a complex of five villages within a 10 km radius. Aedes aegypti resting indoors was sampled at four different times of year from houses within the five villages. Genetic markers were used to screen the mosquitoes: two Exon Primed Intron Crossing (EPIC) markers and five microsatellite markers. The raw allele size was determined using several statistical software packages to analyze the population structure of the mosquito. Estimates of effective population size for each village were low, but there was no evidence of genetic isolation by geographic distance. CONCLUSIONS: The presence of temporary genetic structure is possibly caused by genetic drift due to large contributions of adults from a few breeding containers. This suggests that the introduction of mosquitoes into an area needs to proceed through multiple releases and targeting of sites where mosquitoes are emerging in large numbers.


Assuntos
Aedes/fisiologia , Variação Genética , Insetos Vetores , Aedes/classificação , Aedes/genética , Animais , Dengue/epidemiologia , Dengue/prevenção & controle , Marcadores Genéticos , Humanos , Controle de Mosquitos/métodos , Tailândia/epidemiologia
19.
Trials ; 13: 212, 2012 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-23153360

RESUMO

BACKGROUND: There is an urgent need to protect children against dengue since this age group is particularly sensitive to the disease. Since dengue vectors are active mainly during the day, a potential target for control should be schools where children spend a considerable amount of their day. School uniforms are the cultural norm in most developing countries, worn throughout the day. We hypothesise that insecticide-treated school uniforms will reduce the incidence of dengue infection in school-aged children. Our objective is to determine the impact of impregnated school uniforms on dengue incidence. METHODS: A randomised controlled trial will be conducted in eastern Thailand in a group of schools with approximately 2,000 students aged 7-18 years. Pre-fabricated school uniforms will be commercially treated to ensure consistent, high-quality insecticide impregnation with permethrin. A double-blind, randomised, crossover trial at the school level will cover two dengue transmission seasons. DISCUSSION: Practical issues and plans concerning intervention implementation, evaluation, analysing and interpreting the data, and possible policy implications arising from the trial are discussed. TRIAL REGISTRATION: clinicaltrial.gov. REGISTRATION NUMBER: NCT01563640.


Assuntos
Dengue/prevenção & controle , Controle de Insetos/métodos , Inseticidas , Permetrina , Roupa de Proteção , Projetos de Pesquisa , Instituições Acadêmicas , Adolescente , Animais , Criança , Análise Custo-Benefício , Estudos Cross-Over , Dengue/economia , Dengue/epidemiologia , Dengue/transmissão , Dengue/virologia , Países em Desenvolvimento , Vetores de Doenças , Método Duplo-Cego , Custos de Cuidados de Saúde , Humanos , Incidência , Controle de Insetos/economia , Inseticidas/economia , Permetrina/economia , Roupa de Proteção/economia , Estações do Ano , Tailândia/epidemiologia , Fatores de Tempo , Populações Vulneráveis
20.
Interdiscip Perspect Infect Dis ; 2012: 907494, 2012.
Artigo em Inglês | MEDLINE | ID: mdl-23056042

RESUMO

This study analyzed the association between household-level ecologic and individual-level sociodemographic determinants and dengue transmission in urban areas of Chachoengsao province, Thailand. The ecologic and sociodemographic variables were examined by univariate analysis and multivariate logistic regression. In the ecologic model, dengue risk was related to households situated in the ecotope of residential mixed with commercial and densely populated urban residential areas (RCDENPURA) (aOR = 2.23, P = 0.009), high historical dengue risk area (aOR = 2.06, P < 0.001), and presence of household window screens (aOR = 1.62, P = 0.023). In the sociodemographic model, the dengue risk was related to householders aged >45 years (aOR = 3.24, P = 0.003), secondary and higher educational degrees (aOR = 2.33, P = 0.013), household members >4 persons (aOR = 2.01, P = 0.02), and community effort in environmental management by clean-up campaign (aOR = 1.91, P = 0.035). It is possible that the preventive measures were positively correlated with dengue risk because these activities were generally carried out in particular households or communities following dengue experiences or dengue outbreaks. Interestingly, the ecotope of RCDENPURA and high historical dengue risk area appeared to be very good predictors of dengue incidences.

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