[Show abstract][Hide abstract] ABSTRACT: 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.
International Journal of Environmental Research and Public Health 01/2014; 11(1):934-51. · 2.00 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: 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.
[Show abstract][Hide abstract] ABSTRACT: 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.
Global Health Action 01/2014; 7:24887. · 2.06 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: 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.
PLoS ONE 01/2014; 9(9):e108017. · 3.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: 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.
International journal of environmental research and public health. 01/2014; 11(10):10694-10709.
[Show abstract][Hide abstract] ABSTRACT: 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.
Global Health Action 01/2013; 6:1-6. · 2.06 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: 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.
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.
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.
[Show abstract][Hide abstract] ABSTRACT: 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.
[Show abstract][Hide abstract] ABSTRACT: Research has shown that the classical Stegomyia indices (or "larval indices") of the dengue vector Aedes aegypti reflect the absence or presence of the vector but do not provide accurate measures of adult mosquito density. In contrast, pupal indices as collected in pupal productivity surveys are a much better proxy indicator for adult vector abundance. However, it is unknown when it is most optimal to conduct pupal productivity surveys, in the wet or in the dry season or in both, to inform control services about the most productive water container types and if this pattern varies among different ecological settings.
A multi-country study in randomly selected twelve to twenty urban and peri-urban neighborhoods ("clusters") of six Asian countries, in which all water holding containers were examined for larvae and pupae of Aedes aegypti during the dry season and the wet season and their productivity was characterized by water container types. In addition, meteorological data and information on reported dengue cases were collected.
The study reconfirmed the association between rainfall and dengue cases ("dengue season") and underlined the importance of determining through pupal productivity surveys the "most productive containers types", responsible for the majority (>70%) of adult dengue vectors. The variety of productive container types was greater during the wet than during the dry season, but included practically all container types productive in the dry season. Container types producing pupae were usually different from those infested by larvae indicating that containers with larval infestations do not necessarily foster pupal development and thus the production of adult Aedes mosquitoes.
Pupal productivity surveys conducted during the wet season will identify almost all of the most productive container types for both the dry and wet seasons and will therefore facilitate cost-effective targeted interventions.
Pathogens and global health. 12/2012; 106(8):436-45.
[Show abstract][Hide abstract] ABSTRACT: Dengue is considered one of the most important vector-borne diseases in Thailand. Its incidence is increasing despite routine implementation of national dengue control programmes. This study, conducted during 2010, aimed to demonstrate an application of integrated, community-based, eco-bio-social strategies in combination with locally-produced eco-friendly vector control tools in the dengue control programme, emphasizing urban and peri-urban settings in eastern Thailand.
Three different community settings were selected and were randomly assigned to intervention and control clusters. Key community leaders and relevant governmental authorities were approached to participate in this intervention programme. Ecohealth volunteers were identified and trained in each study community. They were selected among active community health volunteers and were trained by public health experts to conduct vector control activities in their own communities using environmental management in combination with eco-friendly vector control tools. These trained ecohealth volunteers carried out outreach health education and vector control during household visits. Management of public spaces and public properties, especially solid waste management, was efficiently carried out by local municipalities. Significant reduction in the pupae per person index in the intervention clusters when compared to the control ones was used as a proxy to determine the impact of this programme.
Our community-based dengue vector control programme demonstrated a significant reduction in the pupae per person index during entomological surveys which were conducted at two-month intervals from May 2010 for the total of six months in the intervention and control clusters. The programme also raised awareness in applying eco-friendly vector control approaches and increased intersectoral and household participation in dengue control activities.
An eco-friendly dengue vector control programme was successfully implemented in urban and peri-urban settings in Thailand, through intersectoral collaboration and practical action at household level, with a significant reduction in vector densities.
Pathogens and global health. 12/2012; 106(8):446-54.
[Show abstract][Hide abstract] ABSTRACT: 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 Registrationclinicaltrial.govRegistration number: NCT01563640.
[Show abstract][Hide abstract] ABSTRACT: BACKGROUND: Appropriate supervision, along with availability of an effective system for monitoring and evaluation, is a crucial requirement to guarantee sufficient coverage and quality of malaria vector control procedures. This study evaluated the efficacy of self-assessment practice as a possible innovative method towards achieving high coverage and excellent quality of larviciding operation in Iran. METHODS: The research was conducted on the randomly selected rural health centre of Kanmbel Soliman with 10 staff and 30 villages, in three main steps: (i) assessment of effectiveness of larviciding operations in the study areas before intervention through external assessment by a research team; (ii) self-assessment of larviciding operations (intervention) by staff every quarter for three rounds; and, (iii) determining the effectiveness of applying self-assessment of larviciding operations in the study areas. Two toolkits were used for self-assessment and external evaluation. The impact of self-assessment of larviciding operations was measured by two indicators: percentage of missed breeding habitats and cleaned breeding habitats among randomly selected breeding sites. Moreover, the correlation coefficients were measured between self-assessment measures and scores from external evaluation. The correlation coefficient and Mann Whitney test were used to analyse data. RESULTS: Following the utilization of self-assessment, the percentage of missed breeding habitats decreased significantly from 14.23% to 1.91% (P <0.001). Additionally, the percentage of cleaned breeding habitats among randomly selected breeding sites increased from 66.89% to 95.28% (P <0.001). The external evaluation also showed significant effects of selfassessment in performance of vector control; the maximum effect of intervention were seen in an action plan for monitoring and evaluation of larviciding operations at field level, geographical reconnaissance for the registration of breeding habitats and worker skills related to larviciding. Before intervention, the results of self-assessment practice were compatible with external evaluation in 76.3% of 139 reviewed reports of self-assessment. After intervention, the findings of self-assessment and external evaluation were similar in the vast majority of reviewed reports (95%). CONCLUSION: The self-assessment tool seems to be valid and reliable in improving effectiveness of larviciding operations. Furthermore, the result of self-assessment is more compatible with external evaluation results if it would be applied frequently. Therefore, it can be used as an alternative assessment technique in the evaluation of larviciding operations in addition to traditional assessment methods.
[Show abstract][Hide abstract] ABSTRACT: Dengue fever is a mosquito-borne viral disease estimated to cause about 230 million infections worldwide every year, of which 25,000 are fatal. Global incidence has risen rapidly in recent decades with some 3.6 billion people, over half of the world's population, now at risk, mainly in urban centres of the tropics and subtropics. Demographic and societal changes, in particular urbanization, globalization, and increased international travel, are major contributors to the rise in incidence and geographic expansion of dengue infections. Major research gaps continue to hamper the control of dengue. The European Commission launched a call under the 7th Framework Programme with the title of 'Comprehensive control of Dengue fever under changing climatic conditions'. Fourteen partners from several countries in Europe, Asia, and South America formed a consortium named 'DengueTools' to respond to the call to achieve better diagnosis, surveillance, prevention, and predictive models and improve our understanding of the spread of dengue to previously uninfected regions (including Europe) in the context of globalization and climate change.The consortium comprises 12 work packages to address a set of research questions in three areas:Research area 1: Develop a comprehensive early warning and surveillance system that has predictive capability for epidemic dengue and benefits from novel tools for laboratory diagnosis and vector monitoring.Research area 2: Develop novel strategies to prevent dengue in children.Research area 3: Understand and predict the risk of global spread of dengue, in particular the risk of introduction and establishment in Europe, within the context of parameters of vectorial capacity, global mobility, and climate change.In this paper, we report on the rationale and specific study objectives of 'DengueTools'. DengueTools is funded under the Health theme of the Seventh Framework Programme of the European Community, Grant Agreement Number: 282589 Dengue Tools.
Global Health Action 01/2012; 5. · 2.06 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: 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.
Interdisciplinary Perspectives on Infectious Diseases 01/2012; 2012:907494.
[Show abstract][Hide abstract] ABSTRACT: One of the great challenges in the ecology of infectious diseases is to understand what drives the emergence of new pathogens including the relationship between viruses and their hosts. In the case of the emergence of SevereAcute Respiratory Syndrome Coronavirus (SARS-CoV), several studies have shown coronavirus diversity in bats as well as the existence of SARS-CoV infection in apparently healthy bats, suggesting that bats may be a crucial host in the genesis of this disease. To elucidate the biogeographic origin of SARS-CoV and investigate the role that bats played in its emergence, we amplified coronavirus sequences from bat species captured throughout Thailand and assessed the phylogenetic relationships to each other and to other published coronavirus sequences. To this end, RdRp sequence of Coronavirinae was targeted by RT-PCR in non-invasive samples from bats collected in Thailand. Two new coronaviruses were detected in two bat species: one Betacoronavirus in Hipposideros larvatus and one Alphacoronavirus in Hipposiderosarmiger. Interestingly, these viruses from South-East Asia are related to those previously detected in Africa (Betacoronavirus-b) or in Europe (Alphacoronavirus & Betacoronavirus-b). These findings illuminate the origin and the evolutionary history of the SARS-CoV group found in bats by pushing forward the hypothesis of a Betacoronavirus spill-over from Hipposideridae to Rhinolophidae and then from Rhinolophidae to civets and Human. All reported Betacoronaviruses-b (SARS-CoV group) of Hipposideridae and Rhinolophidae respectively cluster in two groups despite their broad geographic distribution and the sympatry of their hosts, which is in favor of an ancient and genetically independent evolution of Betacoronavirus-b clusters in these families. Moreover, despite its probable pathogenicity, we found that a Betacoronavirus-b can persistently infect a medium-sized hipposiderid bat colony. These findings illustrate the importance of the host phylogeny and the host/pathogen ecological interactions in the description and the understanding of pathogen emergence. The host's phylogeny, biogeography and behaviour, combined with already described roles of pathogen plasticity and anthropic changes are likely to be co-factors of disease emergence. Elucidating the common ancestor of Hipposideridae and Rhinolophidae is key to understanding the evolutionary history of actual betacoronaviruses and therefore to get an insight of the deep origin of SARS-CoV.
Infection, genetics and evolution: journal of molecular epidemiology and evolutionary genetics in infectious diseases 07/2011; 11(7):1690-702. · 3.22 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Wolbachia bacteria are common cytoplasmic symbionts of insects, mites and filarial nematodes. They can alter the reproduction of their hosts. The symbiont could be eliminated, transferred or used through genetic alteration to take advantage or remove their possible influences on pests and/or natural enemies. Their extensive effects on reproduction and host fitness have made Wolbachia the subject of growing attention as a potential biocontrol agent. Here, we summarize the relations of Wolbachia in the control of disease vectors and pests. Furthermore, the drawbacks of these bacteria are also discussed.
[Show abstract][Hide abstract] ABSTRACT: Dengue infection causes a significant economic, social and medical burden in affected populations in over 100 countries in the tropics and sub-tropics. Current dengue control efforts have generally focused on vector control but have not shown major impact. School-aged children are especially vulnerable to infection, due to sustained human-vector-human transmission in the close proximity environments of schools. Infection in children has a higher rate of complications, including dengue hemorrhagic fever and shock syndromes, than infections in adults. There is an urgent need for integrated and complementary population-based strategies to protect vulnerable children. We hypothesize that insecticide-treated school uniforms will reduce the incidence of dengue in school-aged children. The hypothesis would need to be tested in a community based randomized trial. If proven to be true, insecticide-treated school uniforms would be a cost-effective and scalable community based strategy to reduce the burden of dengue in children.
Medical Hypotheses 03/2011; 76(6):861-2. · 1.18 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We have used real-time quantitative PCR to measure, for the first time, the relative phage WO-B orf7 density and infection incidence in Aedes albopictus mosquitoes from fields in Thailand. Our results showed that the infection incidence of phage WO-B in this mosquito, sampled from geographically different places in Thailand, was 97.9%. Average relative densities of the offspring were different when collected from diverse parts and reared under the same conditions in the laboratory. Our results also revealed that geographical differences within Thailand did not influence the maternal transmission rate of bacteriophage WO-B. In addition, the orf7 loci might not be strictly associated with Wolbachia, because less than 100% of them were maternally inherited. This discovery does not support the hypothesis that bacteriophage WO-B is involved in Aedes albopictus' cytoplasmic incompatibility. Whether this bacteriophage actually is involved in Wolbachia-induced cytoplasmic incompatibility in this mosquito thus needs further investigation, and additional densities of phage WO-B loci should be integrated.
Current Microbiology 10/2010; 62(3):816-20. · 1.52 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Wolbachia are maternally inherited bacteria that cause various reproductive alterations in their arthropod hosts, including cytoplasmic incompatibility. In this study, we compared mating, oviposition, and host-seeking behavior of Wolbachia-infected (Houston [HOU], Gainesville [GNV]) and Houston uninfected (HT1) Aedes albopictus. In mating assays with virgin mosquitoes, mating success of Wolbachia-infected males was significantly higher than uninfected strains. Mating success was highest with HOU males exposed to infected (95%) and uninfected females (100%), and lowest with HT1 males exposed to infected (20%) and uninfected (25%) females. Results suggested that Wolbachia infection may influence the reproductive behavior of this mosquito. There were no clear differences in oviposition responses between strains, with all strains ovipositing significantly more often on hay infusion and larval rearing water than on water controls and least frequently on 4-methylphenol. Strains of Ae. albopictus females were host-seeking a human when given a choice. Responses to a human arm, acetone, CO2, and dichloromethane were generally higher from the Houston strains than from the GNV strain. Responses of HOU and HT1 females differed from GNV with greater responses to the arm and CO2.
Journal of the American Mosquito Control Association 09/2010; 26(3):265-73. · 0.76 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To study dengue vector breeding patterns under a variety of conditions in public and private spaces; to explore the ecological, biological and social (eco-bio-social) factors involved in vector breeding and viral transmission, and to define the main implications for vector control.
In each of six Asian cities or periurban areas, a team randomly selected urban clusters for conducting standardized household surveys, neighbourhood background surveys and entomological surveys. They collected information on vector breeding sites, people's knowledge, attitudes and practices surrounding dengue, and the characteristics of the study areas. All premises were inspected; larval indices were used to quantify vector breeding sites, and pupal counts were used to identify productive water container types and as a proxy measure for adult vector abundance.
The most productive vector breeding sites were outdoor water containers, particularly if uncovered, beneath shrubbery and unused for at least one week. Peridomestic and intradomestic areas were much more important for pupal production than commercial and public spaces other than schools and religious facilities. A complex but non-significant association was found between water supply and pupal counts, and lack of waste disposal services was associated with higher vector abundance in only one site. Greater knowledge about dengue and its transmission was associated with lower mosquito breeding and production. Vector control measures (mainly larviciding in one site) substantially reduced larval and pupal counts and "pushed" mosquito breeding to alternative containers.
Vector breeding and the production of adult Aedes aegypti are influenced by a complex interplay of factors. Thus, to achieve effective vector management, a public health response beyond routine larviciding or focal spraying is essential.
Bulletin of the World Health Organisation 03/2010; 88(3):173-84. · 5.25 Impact Factor