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- Kittayapong, P, et al.
(author)
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A school-based intervention trial using insecticide-treated school uniforms to reduce dengue infections in school-aged children
- 2015
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In: Tropical medicine & international health. - : Wiley-Blackwell. - 1360-2276 .- 1365-3156. ; 20:Suppl. 1, s. 114-114
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Journal article (other academic/artistic)abstract
- Background: There is an urgent need to enhance our armamentarium to prevent dengue infections in children. Since dengue vectors (Aedes mosquitoes) 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 hypothesized that insecticide-treated school uniforms will reduce the incidence of dengue infection in school-aged children. Our objective was to determine the impact of impregnated school uniforms on dengue incidence.Methods: A randomised controlled trial was conducted in 10 schools in eastern Thailand in 2012. Pre-fabricated school uniforms were commercially treated to ensure consistent high quality of insecticide impregnation with permethrin. The 1-h-knock-down effect and 24 h mortality of Aedes mosquitoes by the impregnated cloth was tested at baseline and then once per month using WHOPES cone test. Blood samples were taken at baseline and at the end of the school-term for the hemagglutination-inhibition assay to identify serologically confirmed dengue infections during the study period. Students were randomized into intervention schools (all students wearing impregnated uniforms) versus control schools (uniforms had the same appearance and odor, but were not impregnated).Results: A total of 1808 students in 10 schools were enrolled, mean age 10.07 years. Of these, 1651 had paired blood samples taken, which showed an incidence of new dengue infection of 3.3 % over the school term (5 months). There was no difference in the incidence of dengue infections in intervention versus control schools. Both the knock-down and mortality at baseline were close to 100%, but rapidly waned after only 8 washes to 20% e.g. after only 1 month of wearing the uniform.Conclusion: Although the results of mosquitoes’ knock-down and mortality of impregnated schools looked very promising, we did not see a protective effect of impregnated uniforms on reducing dengue infections in this school-based trial. The most likely reason for the apparent failure was the rapid waning efficacy of impregnation after washing. New technologies need to be developed to overcome rapid waning efficacy of impregnated clothing.Disclosure: This research was funded by the European Commission 7th Framework and was conducted by ‘DengueTools’ partners.
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| 5. |
- Ratanawong, P, et al.
(author)
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Exploring entomological factors associated with high dengue incidence in Thai schools
- 2015
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In: Tropical medicine & international health. - : Wiley-Blackwell. - 1360-2276 .- 1365-3156. ; 20:Suppl. 1, s. 411-411
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Journal article (other academic/artistic)abstract
- Introduction: Dengue infection is a leading cause of child hospitalization in Thailand and schools may represent an important site of infection. Because high variations in the number of dengue cases were observed among schools, the aim of this study was to explore what entomological factors were associated with high dengue incidence in selected schools located in Chacheongsao Province, Thailand.Methods: Students from ten schools were enrolled; blood was taken at baseline (June 2012) and at the end of the school term (Nov. 2012). New dengue infections during this period were determined by dengue IgG conversion or a > 4-fold higher dengue IgG compared to baseline. Location of the homes and schools of infected students were mapped using GIS. Through monthly surveys from May 2013 to June 2014, potential breeding sites were identified, infestation with Aedes larvae and pupae recorded, and adult mosquitoes collected using portable aspirators. Logistic regression was used for statistical analysis.Results: A total of 1825 students were included in the study. They were distributed among 88 classrooms within the 10 schools. 55 confirmed dengue cases were detected in seven of the 10 schools. 67% of the cases occurred in 13 (15%) of the 88 classrooms, with at least 2 (and as many as 6) cases occurring per classroom. The remaining 18 cases were detected as single cases per classroom. No two cases occurred in the same households and eight cases occurred in households distant 100 meters or less from each other. There was no direct association between high and low incidence schools in relation to the number of breeding sites, mosquitoes, or mosquito control methods used. Of the 2399 potential breeding sites recorded, 484 (20%) were positive for Aedes larvae or pupae. Among the productive sites, the most common were water and cement tanks (30%) and car tires (9%). Mosquito control was used for 11% of breeding sites, with temephos (32%), fish (24%) and covers (30%) being the most common measures taken.Conclusion: The study provides information on the main breeding sites for larvae and pupae and the commonly used mosquito control methods around schools. Although there was no significant association found between entomological factors and dengue cases at school levels, the study suggests that transmission may be clustered at classroom level rather than at household level.Disclosure: This research was funded by the European Union 7th Framework Programme through 'DengueTools'.
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- Wai, K. T., et al.
(author)
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Estimating dengue vector abundance in the wet and dry season: implications for targeted vector control in urban and peri-urban Asia
- 2012
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In: Pathogens and Global Health. - : Informa UK Limited. - 2047-7724 .- 2047-7732. ; 106:8, s. 436-445
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Journal article (peer-reviewed)abstract
- Background: 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. Methods: 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. Findings: 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. Conclusion: 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.
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| 7. |
- Kittayapong, P, et al.
(author)
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Efficacy of permethrin-impregnated clothing on knock-down and mortality of dengue mosquito vectors
- 2015
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In: Tropical medicine & international health. - : Wiley-Blackwell. - 1360-2276 .- 1365-3156. ; 20:Suppl. 1, s. 110-110
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Journal article (other academic/artistic)abstract
- Introduction: As vector control for dengue has proven to be elusive, additional methods to protect against dengue are urgently needed. We have previously shown that pre-fabricated clothing impregnated with permethrin in a proprietary manner had a close to 100% 1 h knock-down and 24 h-mortality effect on Aedes mosquito vectors. However, this effect rapidly declined with repeated washing. Here we investigated different impregnation techniques to assess the best method with the lowest waning efficacy after washing. Materials and methods School clothes were impregnated with permethrin by two different technologies: pad-dry-cure versus exhaustion. Impregnated products were tested for their efficacy using laboratory-reared Aedes mosquito vectors using WHOPES cone test, before and after 10 washes.Results: The 1 h knock down effect and 24 h mortality rate of school clothes treated by both technologies were both found to be 100%. However, the clothes treated by pad-dry-cure technology could stand frequent washing better than those treated by exhaustion technology. The decrease in efficacy of up to about 60% of the clothes treated by pad-dry-cure technology was observed after washing 8 times while those treated by exhaustion technology showed decrease in knock-down effect (67.27%) and mortality rate (74.29%) after washing only 4 times.Conclusion: The knock-down and 24 h mortality results look very promising to support impregnated clothing as a potential strategy to protect against day-biting Aedes mosquito vectors to prevent dengue infections. However, rapid waning efficacy of impregnated clothing after <10 washes suggests that impregnation techniques for sustainable effect are sub-optimal and hence such an approach is not recommended at this point in time. Either new impregnation technologies will need to be developed to overcome the waning efficacy after washing, or clothing such as aprons or vests will need to be employed. Since school aprons are hanged in classrooms after daily use without washing through out the school term, they could potentially have a prolonged impact of permethrin on mosquito vectors (in terms of knock-down and mortality) and eventually dengue transmission in school.This research was funded by the European Union 7th Frame- work Programme through ‘DengueTools’ and Mahidol University.Disclosure: Nothing to disclose
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- Wilder-Smith, Annelies, et al.
(author)
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Hypothesis : Impregnated school uniforms reduce the incidence of dengue infections in school children
- 2011
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In: Medical Hypotheses. - : Elsevier. - 0306-9877 .- 1532-2777. ; 76:6, s. 861-862
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Journal article (peer-reviewed)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.
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