Importance of improved housing for reducing infectious diseases of children in sub-Saharan Africa

Abstract

Since 2000, housing in sub-Saharan Africa (SSA) has markedly improved due to significant economic progress in the region. However, the majority of these improvements are concentrated in urban settings, leaving rural areas, primarily inhabited by impoverished communities, exposed to substandard housing and heightened risks of communicable diseases such as malaria, diarrhoea, and respiratory illnesses. Consequently, there is an imperative to devise healthier housing solutions to shield children in these communities from communicable diseases.
The screening of windows, open eaves and doors has been demonstrated to effectively reduce malaria transmission, parasitaemia, and anaemia in children. Additionally, homes equipped with constant access to clean water, proper latrines, improved flooring, and sewage systems exhibit a lower incidence of diarrheal diseases compared to those lacking these amenities. Well-ventilated houses, characterized by ample and strategically positioned windows, manifest a decreased risk of respiratory diseases such as tuberculosis.
In northern Tanzania, a novel two-storey house, featuring mosquito screens and designed to combat malaria, was piloted and demonstrated a significant reduction in the entry of malaria mosquitoes. The prototype, named the ‘Star home’, not only aims to diminish malaria but also seeks to lower the incidence of diarrheal and respiratory infections in young children compared to traditional house types. A household randomized-controlled trial assessing the impact of Star homes on the incidence of these diseases commenced in January 2022 in rural Mtwara in southern Tanzania.
My PhD evaluated the efficacy of Star homes in reducing mosquito and fly entry compared to traditional dwellings. The study comprises three parts: 1) pilot study to assess whether the light-permeable walls and the narrow eaves gaps found in Star homes increase mosquito entry in experimental huts, 2) the household RCT measuring mosquito and housefly densities, and 3) the potential risk factors contributing to the indoor abundances of malaria vectors was assessed using the traditional house type. This trial also evaluated indoor and outdoor temperature, relative humidity, and carbon dioxide levels in both control and intervention groups.
The pilot study demonstrated that transparent-walled huts, allowing light penetration from an indoor CDC light trap, increased indoor An. arabiensis mosquito abundance by 84% compared to opaque-walled huts with limited light visibility. Furthermore, well-ventilated huts reduced indoor An. arabiensis abundances by 99% compared to poorly ventilated traditional houses.
In the randomized controlled trial (RCT), Star homes exhibited a reduction in indoor mosquito density: 54% for Anopheles gambiae s.l., 81% for Anopheles funestus s.l., and 64% for Culex species. Moreover, Star homes decreased the risk of malaria transmission by 55% when contrasted with traditional houses. No discernible effects were observed on indoor environmental conditions measurements (temperature, relative humidity, and CO2 concentrations) between Star homes and traditional houses. The main external doors of Star homes were open for 60% less time than those in traditional houses.
The Star homes also decreased domestic fly populations by over 40% in kitchens, with a 46% reduction specifically observed in Chrysomyia putoria populations in toilets compared to traditional houses.
When assessing potential risks factors for indoor malaria vectors (gambiae s.l. and An. funestus s.l.) hotspots for indoor malaria vectors were identified in the central and far eastern regions of the study area. Proximity to open water bodies within 15 m of a traditional house amplified indoor malaria vector abundances by 61%, while open windows doubled their presence. Conversely, increased built-up areas reduced indoor malaria vector abundance by 99%, each 100 m increase in altitude decreased it by 29%, and the presence of chickens in peri-domestic areas was associated with an 8% reduction in malaria vector abundance.
The pilot study findings informed the selection of a suitable mosquito trapping method and the design of Star homes used in the main trial. The main study emphasizes integrating various previously identified beneficial housing design elements, such as screened windows and doors, sealed eave gaps, and toilet designs with blocked main holes and smoothly cemented floors. These measures aim to minimize mosquito and non-hematophagous fly entry into dwellings, thereby reducing the transmission risk of multiple infections to children in rural areas of sub-Saharan Africa (SSA). Additionally, the results underscore the importance of improving drainage around nearby open water bodies or implementing larviciding measures to decrease malaria vector populations in the vicinity