Abstract
BackgroundConstruction of the Nam Theun 2 hydroelectric project and flooding of a 450 km2 area of mountain plateau in south-central Lao PDR resulted in the resettlement of 6,300 people to newly built homes. We examined whether new houses would have altered risk of house entry by mosquitoes compared with traditional homes built from poorer construction materials.Methodology/Principal FindingsSurveys were carried out in the Nam Theun 2 resettlement area and a nearby traditional rice farming area in 2010. Mosquitoes were sampled in bedrooms using CDC light traps in 96 resettlement houses and 96 traditional houses and potential risk factors for mosquito house entry were recorded. Risk of mosquito house entry was more than twice as high in traditional bamboo houses compared with those newly constructed from wood (Putative Japanese Encephalitis (JE) vector incidence rate ratio (IRR) = 2.26, 95% CI 1.38–3.70, P = 0.001; Anopheline IRR = 2.35, 95% CI: 1.30–4.23, P = 0.005). Anophelines were more common in homes with cattle compared against those without (IRR = 2.32, 95% CI: 1.29–4.17, P = 0.005).Wood smoke from cooking fires located under the house or indoors was found to be protective against house entry by both groups of mosquito, compared with cooking in a separate room beside the house (Putative JE vector IRR = 0.43, 95% CI: 0.26–0.73, P = 0.002; Anopheline IRR = 0.22, 95% CI: 0.10–0.51, P<0.001).Conclusions/SignificanceConstruction of modern wooden homes should help reduce human-mosquito contact in the Lao PDR. Reduced mosquito contact rates could lead to reduced transmission of diseases such as JE and malaria. Cattle ownership was associated with increased anopheline house entry, so zooprophylaxis for malaria control is not recommended in this area. Whilst wood smoke was protective against putative JE vector and anopheline house entry we do not recommend indoor cooking since smoke inhalation can enhance respiratory disease.
Highlights
Mosquito house entry can be reduced through simple changes in house design, such as closing eaves, installing a ceiling, screening external doors and windows and a general improvement in quality of construction materials [1]
A recent randomised controlled trial of house screening in The Gambia showed that installing screened ceilings or full screening of houses with fly-screened doors and windows, and closing the eaves resulted in a 50% decline in the risk of anaemia due to malaria, a major killer of young children [6]
Our analysis of risk factors for house entry by putative vectors of Japanese encephalitis (JE) and malaria shows that in the Nam Theun 2 (NT2) resettlement area and in a traditional rice farming area immediately downstream of the reservoir, the type of housing and how people use their house affects the risk of mosquitoes entering bedrooms and presumably the risk of mosquitoes biting residents of these houses
Summary
Mosquito house entry can be reduced through simple changes in house design, such as closing eaves, installing a ceiling, screening external doors and windows and a general improvement in quality of construction materials [1]. In these instances house entry rates are probably reduced by physically blocking or decreasing the number of holes through which a mosquito may gain access to a home. A recent randomised controlled trial of house screening in The Gambia showed that installing screened ceilings or full screening of houses with fly-screened doors and windows, and closing the eaves resulted in a 50% decline in the risk of anaemia due to malaria, a major killer of young children [6]. We examined whether new houses would have altered risk of house entry by mosquitoes compared with traditional homes built from poorer construction materials
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