Assessing the impact of a novel house design on the incidence of malaria in children in rural Africa: study protocol for a household-cluster randomized controlled superiority trial
Abstract:Background
Traditional rural housing in hot, humid regions of sub-Saharan Africa usually consists of single-level, poorly ventilated dwellings. Houses are mostly poorly screened against malaria mosquitoes and limited airflow discourages the use of bednets resulting in high indoor transmission. This study aims to determine whether living in a novel design house with elevated bedrooms and permeable screened walls reduces malaria, respiratory tract infections, and diarrhoea among children in rural… Show more
“…This study is subject to several limitations. Our characterization of housing was constrained by the availability of data from household surveys, which generally only ask about just three components, and don't include questions about other relevant features of the built household environment, such as screens covering openings [62] elevation of sleeping areas or improvements to windows and ventilation [63]. Although the variables were originally in three-class ordinal categorical format, we had to combine categories and model them as dichotomous, because there is currently no way to address adjacent categories and parallel odds using the INLA modeling approach.…”
Section: Discussionmentioning
confidence: 99%
“…enter the home through eaves and other openings [64] and rest on walls and ceilings after ingesting a blood meal (the basis behind indoor residual spraying [IRS] of these surfaces as a malaria control intervention). Indeed, in Africa, 80% of malaria transmission occurs indoors [3] and houses with roofs and walls constructed of natural material provide more points of entry [64,65] and preferred resting places [66] for malaria-transmitting mosquitoes, insights which are increasingly putting housing improvements on the research agendas as potential disease control strategies [63,65]. In rural Gambia, studies have found reductions in intradomiciliary mosquito vector abundance and survival through installing plywood ceilings [67], closing eaves in thatched roofs [68,69], and replacing thatch with ventilated metal roofing [70].…”
Housing infrastructure and quality is a major determinant of infectious disease risk and other health outcomes in regions of the world where vector borne, waterborne and neglected tropical diseases are endemic. It is important to quantify the geographical distribution of improvements to the major dwelling components to identify and target resources towards populations at risk. The aim of this study was to model the sub-national spatial variation in housing materials using covariates with quasi-global coverage and use the resulting estimates to map the predicted coverage across the world’s low- and middle-income countries (LMICs). Data relating to the materials used in dwelling construction were sourced from nationally representative household surveys conducted since 2005. Materials used for construction of flooring, walls, and roof were reclassified as improved or unimproved. Households lacking location information were georeferenced using a novel methodology, and a suite of environmental and demographic spatial covariates were extracted at those locations for use as model predictors. Integrated nested Laplace approximation (INLA) models were fitted to obtain and map predicted probabilities for each dwelling component. The dataset compiled included information from households in 283,000 clusters from 350 surveys. Low coverage of improved housing was predicted across the Sahel and southern Sahara regions of Africa, much of inland Amazonia, and areas of the Tibetan plateau. Coverage of improved roofs and walls was high in the Central Asia, East Asia and Pacific and Latin America and the Caribbean regions, while improvements in all three components, but most notably floors, was low in Sub-Saharan Africa. Human development was by far the strongest determinant of dwelling component quality, though vegetation greenness and land use were also relevant markers These findings are made available to the reader as files that can be imported into a GIS for integration into relevant analysis to derive improved estimates of preventable health burdens attributed to housing.
“…This study is subject to several limitations. Our characterization of housing was constrained by the availability of data from household surveys, which generally only ask about just three components, and don't include questions about other relevant features of the built household environment, such as screens covering openings [62] elevation of sleeping areas or improvements to windows and ventilation [63]. Although the variables were originally in three-class ordinal categorical format, we had to combine categories and model them as dichotomous, because there is currently no way to address adjacent categories and parallel odds using the INLA modeling approach.…”
Section: Discussionmentioning
confidence: 99%
“…enter the home through eaves and other openings [64] and rest on walls and ceilings after ingesting a blood meal (the basis behind indoor residual spraying [IRS] of these surfaces as a malaria control intervention). Indeed, in Africa, 80% of malaria transmission occurs indoors [3] and houses with roofs and walls constructed of natural material provide more points of entry [64,65] and preferred resting places [66] for malaria-transmitting mosquitoes, insights which are increasingly putting housing improvements on the research agendas as potential disease control strategies [63,65]. In rural Gambia, studies have found reductions in intradomiciliary mosquito vector abundance and survival through installing plywood ceilings [67], closing eaves in thatched roofs [68,69], and replacing thatch with ventilated metal roofing [70].…”
Housing infrastructure and quality is a major determinant of infectious disease risk and other health outcomes in regions of the world where vector borne, waterborne and neglected tropical diseases are endemic. It is important to quantify the geographical distribution of improvements to the major dwelling components to identify and target resources towards populations at risk. The aim of this study was to model the sub-national spatial variation in housing materials using covariates with quasi-global coverage and use the resulting estimates to map the predicted coverage across the world’s low- and middle-income countries (LMICs). Data relating to the materials used in dwelling construction were sourced from nationally representative household surveys conducted since 2005. Materials used for construction of flooring, walls, and roof were reclassified as improved or unimproved. Households lacking location information were georeferenced using a novel methodology, and a suite of environmental and demographic spatial covariates were extracted at those locations for use as model predictors. Integrated nested Laplace approximation (INLA) models were fitted to obtain and map predicted probabilities for each dwelling component. The dataset compiled included information from households in 283,000 clusters from 350 surveys. Low coverage of improved housing was predicted across the Sahel and southern Sahara regions of Africa, much of inland Amazonia, and areas of the Tibetan plateau. Coverage of improved roofs and walls was high in the Central Asia, East Asia and Pacific and Latin America and the Caribbean regions, while improvements in all three components, but most notably floors, was low in Sub-Saharan Africa. Human development was by far the strongest determinant of dwelling component quality, though vegetation greenness and land use were also relevant markers These findings are made available to the reader as files that can be imported into a GIS for integration into relevant analysis to derive improved estimates of preventable health burdens attributed to housing.
Background
Mosquitoes of the Anopheles gambiae complex are one of the major vectors of malaria in sub-Saharan Africa. Their ability to transmit this disease of major public health importance is dependent on their abundance, biting behaviour, susceptibility and their ability to survive long enough to transmit malaria parasites. A deeper understanding of this behaviour can be exploited for improving vector surveillance and malaria control.
Findings
Adult mosquitoes emerge from aquatic habitats at dusk. After a 24 h teneral period, in which the cuticle hardens and the adult matures, they may disperse at random and search upwind for a mate or to feed. Mating generally takes place at dusk in swarms that form over species-specific ‘markers’. Well-nourished females may mate before blood-feeding, but the reverse is true for poorly-nourished insects. Females are monogamous and only mate once whilst males, that only feed on nectar, swarm nightly and can potentially mate up to four times. Females are able to locate hosts by following their carbon dioxide and odour gradients. When in close proximity to the host, visual cues, temperature and relative humidity are also used. Most blood-feeding occurs at night, indoors, with mosquitoes entering houses mainly through gaps between the roof and the walls. With the exception of the first feed, females are gonotrophically concordant and a blood meal gives rise to a complete egg batch. Egg development takes two or three days depending on temperature. Gravid females leave their resting sites at dusk. They are attracted by water gradients and volatile chemicals that provide a suitable aquatic habitat in which to lay their eggs.
Conclusion
Whilst traditional interventions, using insecticides, target mosquitoes indoors, additional protection can be achieved using spatial repellents outdoors, attractant traps or house modifications to prevent mosquito entry. Future research on the variability of species-specific behaviour, movement of mosquitoes across the landscape, the importance of light and vision, reproductive barriers to gene flow, male mosquito behaviour and evolutionary changes in mosquito behaviour could lead to an improvement in malaria surveillance and better methods of control reducing the current over-reliance on the indoor application of insecticides.
“…Based on the pilot study and taking into account the preferences of residents, the team designed a novel healthy house and set out to run a RCT in rural Tanzania. The new 'Star Home' was designed to protect against three diseases of childhood, responsibility for great childhood mortality in sub-Saharan Africa: malaria, diarrhoea and acute respiratory tract infections [8,9]. Using data from the national malaria control programme and after fact-finding visits, Mtwara Region in south-east Tanzania was selected as a study site: in contrast to the pilot study site in Tanga, malaria transmission remained high and there were few other ongoing and planned health-related studies.…”
Section: Introductionmentioning
confidence: 99%
“…Despite funding and logistical challenges, by early 2021, the construction of 110 Star Homes had been completed across 60 villages in Mtwara Region. With strict eligibility criteria that targeted the poorest families in the communities, households had been selected based on a lottery system [9]. Keys were handed over to the lottery winners (who had been consulted throughout construction) and the study staff were ready to begin assessing the health impact of these new homes.…”
Introduction
The population of Africa set to reach 2 billion by 2050. There is therefore great demand for housing across the continent. Research on modified novel designs for housing is a priority to ensure that these homes are not sites of infection for diseases transmission such as malaria. One trial to assess the protection afforded by novel design houses is underway in Mtwara Region, southeastern Tanzania. After constructing 110 of such homes across 60 villages, project staff encountered a certain reticence of the target population to occupy the homes and were faced with accusations of having nefarious intentions. This article explores these accusations, their impacts on home occupancy and lessons for future housing studies.
Methods
This qualitative study drew on in-depth interviews and focus group discussions with ten occupants of the intervention homes, six community leaders and a further 24 community members. Interviews were recorded, transcribed verbatim and translated to English for qualitative content analysis.
Results
In communities around the Star Homes, during construction and handover, project staff were widely associated with ‘Freemasons’, a term used to practices, secrecy, and other conspiracy theories in rural Tanzania. These connections were attributed to other community members and explained in terms of knowledge deficit or envy, with others hoping to be allocated the home. The stories were embedded in assumptions of reciprocity and suspicions about study motives, linked to limited experience of research. The relationship between the accusations of freemasonry and reticence to occupy the houses was not straightforward, with project staff or relatives playing a role in decisions. The stakes were high, because the recipients of Star Homes were the poorest families in targeted communities.
Conclusion
The results indicate the need for long-term and proactive community engagement, which focuses on building relationships and providing information through recognizable voices and formats. Given the stakes at play in housing interventions, research teams should be prepared for the social upheaval the provision of free new housing can cause.
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