Ecological, Social, and Other Environmental Determinants of Dengue Vector Abundance in Urban and Rural Areas of Northeastern Thailand (original) (raw)
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Asia-Pacific Journal of Science and Technology, 2015
The objectives were to survey Aedes aegypti larval breeding habitats and analyze dengue vector indices. This larval vector survey was conducted in Dongklang village in Ubon Ratchathani province over two years in 2012 and 2013. During each year, dengue vector indices, House Index (HI), Container Index (CI), and Breteau Index (BI), were collected for two periods, dry season (January-April) and wet season (May-August). The number of households infested with larvae in the different years and periods were compared using chi-square test. The results showed in 2012, HI, CI, and BI were 52.7%, 19.9%, and 135.1% respectively in the dry season. In the wet season, the indices decreased. In 2013, dengue vector indices again tended to decrease from dry seasonal to wet seasonal periods. The numbers of households that were infested by Aedes larvae did not differ between years and seasons. Dengue vector indices are alternative methods to predict Aedes mosquito distribution and can be used in the m...
Ecologic and Sociodemographic Risk Determinants for Dengue Transmission in Urban Areas in Thailand
Interdisciplinary Perspectives on Infectious Diseases, 2012
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.
Climatic and social risk factors for Aedes infestation in rural Thailand
Tropical Medicine and International Health, 2003
An intense epidemic of dengue haemorrhagic fever in 1998 prompted the Thai government to investigate the feasibility of focalized vector (Aedes aegypti) control programmes. We tested for correlations of three indices of Aedes larval abundance (housing index, container index and Breteau index) against 38 socio-economic and four climatic variables. Availability of public water wells, existence of transport services and proportion of tin houses were positively associated with larval indices. Private water wells, health education, health insurance coverage, thatched houses and use of firewood for cooking were negatively associated. These probably represent both direct effects on breeding sites (private vs. public wells decrease necessity to store water, and health education may encourage breeding site removal), and more general effects of health-related attitude, housing quality and remoteness from urban areas. Indices were positively associated with daily minimum temperature, an increase in precipitation from the previous month (reflecting the onset of the rainy season) and daily maximum temperatures of approximately 33-34 °C.
BMC Public Health
Background Controlling sites where mosquitos breed is a key strategy in breaking the cycle of infectious transmission of the dengue virus. Preventive behaviors, such as covering water containers with lids and adding temephos (commercially named Abate sand) in water containers are needed to reduce and control mosquito breeding sites. This study aimed to investigate the impact of dengue-preventive behaviors on Aedes immature production. Methods This cross-sectional study used in-person interviews to record occurrence of dengue-preventive behaviors in Bang Kachao, Samut Prakan Province, Thailand. Larval mosquitos in and around houses were observed and recorded, and covered 208 households. Results It was found that 50% of these households had containers for drinking water and 94% used water containers. Covering water containers with effective lids showed the best success among dengue-preventive behaviors for reducing Aedes immature production. Adding temephos in water containers also wa...
Journal of the American Mosquito Control Association
Three villages in urban, transition, and rural areas were selected for the survey to clarify the spatial distribution of Ae. aegypti and Ae. albopictus along an urban-rural ecological gradient. The average number of Ae. aegypti larvae in larvitraps was higher in the urban area than in the rural area, as we expected, whereas the opposite was found for Ae. albopictus, rural area Ͼ urban area. A house survey of larvae-inhabiting containers showed significant differences in the number and composition of these containers among the study areas. Significant differences also were found in the average distance between houses, average tree height, and average percentage of vegetation cover for each house. The seasonal pattern of rainfall recorded in each study area did not show great differences among the study areas. The response of Ae. aegypti and Ae. albopictus to the urban-rural gradient is discussed in relation to the possibility of applying geographic information system techniques to plan the control strategy and surveillance of dengue vectors.
2010
Objective 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. Methods 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. Findings 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. Conclusion 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.
Tropical biomedicine, 2006
The objective of this study was to elucidate the association of various risk factors with dengue cases reported in Lundu district, Sarawak, by analyzing the interaction between environmental, entomological, socio-demographic factors. Besides conventional entomological, serological and house surveys, this study also used GIS technology to generate geographic and environmental data on Aedes albopictus and dengue transmission. Seven villages were chosen based on the high number of dengue cases reported. A total of 551 households were surveyed. An overall description of the socio-demographic background and basic facilities was presented together with entomological and geographical profiles. For serological and ovitrap studies, systematic random sampling was used. Serological tests indicated that 23.7% of the 215 samples had a history of dengue, either recent or previous infections. Two samples (0.9%) were confirmed by IgM ELISA and 49 samples (22.8%) had IgG responses. A total of 32,838...
Locations and Religious Factors Affecting Dengue Vectors in Nakhon Si Thammarat, Thailand
This study investigated the numbers of Aedes larvae found in relation to the religion of the people, the location of their houses, and the number of water containers in and around the house. We collected our questionnaire survey during April-May 2004 covering two different topographical areas (i.e. seaside and mountainous areas) and two religious factors (i.e. Buddhist and Muslims). We collected samples by using the stratified simple random sampling with a total of 400 households from all communities in 31 sub-districts. The results showed that there were a higher number of Ae. aegypti larvae in water containers in bathrooms, concrete tanks and large water jars than the number of Ae. albopictus larvae in both areas. Ae. albopictus larvae were found in higher numbers at the seaside area than in the mountainous area. On the other hand, the number of small water jars had a higher number of Aedes larvae in the mountainous area than in the seaside area. Considering only large water jars,...
Epidemiology and Infection, 2008
SUMMARYUsing the enumeration district (ED) block level this study looked at the incidence of dengue fever and dengue haemorrhagic fever (DF/DHF) within the Songkhla municipality in Thailand. Each of the 146 blocks in this area were considered as study units and surveyed for their environmental characteristics. A total of 287 cases of DH/DHF occurring in the year 1998 were selected for this study and the location of their homes mapped. Clustering analysis showed point clustering of the homes (P<0·0001) which was probably due to high density habitation, without any actual prevalence of case clustering. There was no evidence of clustering of the ED blocks with an incidence of DF/DHF (P=0·32). DF/DHF incidence for each block was strongly associated with the percentages of shop-houses, brick-made houses and houses with poor garbage disposal (all…
Trop Biomed, 2006
The objective of this study was to elucidate the association of various risk factors with dengue cases reported in Lundu district, Sarawak, by analyzing the interaction between environmental, entomological, socio-demographic factors. Besides conventional entomological, serological and house surveys, this study also used GIS technology to generate geographic and environmental data on Aedes albopictus and dengue transmission. Seven villages were chosen based on the high number of dengue cases reported. A total of 551 households were surveyed. An overall description of the socio-demographic background and basic facilities was presented together with entomological and geographical profiles. For serological and ovitrap studies, systematic random sampling was used. Serological tests indicated that 23.7% of the 215 samples had a history of dengue, either recent or previous infections. Two samples (0.9%) were confirmed by IgM ELISA and 49 samples (22.8%) had IgG responses. A total of 32,838 Aedes albopictus eggs were collected in 56 days of trapping. Cluster sampling was also done to determine whether any of the risk factors (entomological or geographical) were influenced by geographical location. These clusters were defined as border villages with East Kalimantan and roadside villages along Lundu/Biawas trunk road. The data collected were analyzed using SPSS version 10.01. Descriptive analysis using frequency, means, and median were used. To determine the association between variables and dengue cases reported, and to describe the differences between the two clusters of villages, two-sample t-test, and Pearson's Chi-Square were used. Accurate maps were produced with overlay and density function, which facilitates the map visualization and report generating phases. This study also highlights the use of differential Global Positioning System in mapping sites of 1m accuracy. Analysis of the data revealed there are significant differences in clusters of villages attributable to container density, house density, distance of the house from the main road, and number of Ae. albopictus eggs from ovitraps set indoor, outdoor and in dumping sites (Person's Chi-Square=6.111, df=1, p<0.01). Further analysis using t-test showed that house density, container density, indoor mosquitoes egg count, outdoor mosquitoes egg count, and dumping sites mosquitoes egg count were higher at the roadside villages compared to border villages. A number of potential risk factors including those generated from GIS were investigated. None of the factors investigated in this study were associated with the dengue cases reported.