[Show abstract][Hide abstract] ABSTRACT: Background
Influenza A viruses have the remarkable characteristic of sustainability in the environment. Mucus from snails
contains sialic acids as the one that may allow avian influenza virions to bind to the vertebrate host cell
membrane. Subsequently snails could potentially promote persistence and/or concentration of influenza Avirions
through mucus, in wetland environment when virus is released from bird infected feces.
This article describes experimental research on the potential outcome of apple snails regarding the persistence
and concentration of the H5N1 influenza virions in fresh water. The presence of virus was detected from water
and snails by hemagglutination test, and H5N1 viral genetic material determined by quantitative RT-PCR
Active virus in the water was demonstrated up to twelve days after water infestation without snails, and up to
fourteen days with snails. Also, up to eleven days, the virus and genetic material were detected and tittered from
snails. Although the presence of snails did not significantly change the persistence of H5N1 virus in the water,
number of positive snail sampled and quantitative RT-PCR data suggest that snails may have the ability to
concentrate and carry viral particles.
Ultimately snails could play a role in the virus ecology by concentrating viral particles from water and
facilitating virus contact with the bird hosts that feed on them.
[Show abstract][Hide abstract] ABSTRACT: bstract
Influenza A viruses have the remarkable characteristic of sustainability in the environment. Mucus from snails contains sialic acids as the one that may allow avian influenza virions to bind to the vertebrate host cell membrane. Subsequently snails could potentially promote persistence and/or concentration of influenza Avirions through mucus, in wetland environment when virus is released from bird infected feces.
This article describes experimental research on the potential outcome of apple snails regarding the persistence and concentration of the H5N1 influenza virions in fresh water. The presence of virus was detected from water and snails by hemagglutination test, and H5N1 viral genetic material determined by quantitative RT-PCR
Active virus in the water was demonstrated up to twelve days after water infestation without snails, and up to fourteen days with snails. Also, up to eleven days, the virus and genetic material were detected and tittered from snails. Although the presence of snails did not significantly change the persistence of H5N1 virus in the water, number of positive snail sampled and quantitative RT-PCR data suggest that snails may have the ability to concentrate and carry viral particles.
Ultimately snails could play a role in the virus ecology by concentrating viral particles from water and facilitating virus contact with the bird hosts that feed on them.
[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 10/2014; 11(10):10694-10709. DOI:10.3390/ijerph111010694 · 2.06 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: 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.
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.
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).
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.
PLoS ONE 09/2014; 9(9):e108017. DOI:10.1371/journal.pone.0108017 · 3.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: BackgroundAs 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.ObjectivesThis 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.MethodologyQuantitative 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.ResultsThe 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.ConclusionsAcceptability 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.
Global Health Action 09/2014; 7:24887. DOI:10.3402/gha.v7.24887 · 1.93 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.
Virology 09/2014; s 464–465(1):312–319. DOI:10.1016/j.virol.2014.06.036 · 3.32 Impact Factor
[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. DOI:10.3390/ijerph110100934 · 2.06 Impact Factor
[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: 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.
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.
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.
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 03/2013; 6(1):1-6. DOI:10.3402/gha.v6i0.20473 · 1.93 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: 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.