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Rural houses in sub-Saharan Africa are typically hot and allow malaria mosquitoes inside. We assessed whether passive or active ventilation can reduce house entry of malaria mosquitoes and cool a bedroom at night in rural Gambia. Two identical experimental houses were used: one ventilated and one unventilated (control). We evaluated the impact of (i) passive ventilation (solar chimney) and (ii) active ventilation (ceiling fan) on the number of mosquitoes collected indoors and environmental parameters (temperature, humidity, CO 2 , evaporation). Although the solar chimney did not reduce entry of Anopheles gambiae sensu lato , the ceiling fan reduced house entry by 91% compared with the control house. There were no differences in indoor nightly temperature, humidity or CO 2 between intervention and control houses in either experiment. The solar chimney did not improve human comfort assessed using psychrometric analysis. While the ceiling fan improved human comfort pre-midnight, in the morning it was too cool compared with the control house, although this could be remedied through provision of blankets. Further improvements to the design of the solar chimney are needed. High air velocity in the ceiling fan house probably reduced mosquito house entry by preventing mosquito flight. Improved ventilation in houses may reduce malaria transmission.

Mosquito-transmitted diseases are a major threat to health in sub-Saharan Africa, but could be reduced through modifications to the built environment. Here we report findings from a major workshop held to identify the research gaps in this area, namely: (1) evidence of the health benefits to changes to the built environment, (2) understanding how mosquitoes enter buildings, (3) novel methods for reducing mosquito-house entry, (4) sustainable approaches for reducing mosquito habitats, (5) case studies of micro-financing for healthy homes and (6) methods for increasing scale-up. Multidisciplinary research is essential to build out mosquito-transmitted diseases, and not build them in.

The COVID-19 pandemic has reminded us of the ever present threat from infectious diseases, this includes the ones we know about already and future unknowns. The mosquito-transmitted disease yellow fever has claimed thousands of lives over the centuries and it hasn’t gone away. It is still endemic in tropical areas of Africa and Latin America, where it is kept at bay through constant surveillance, mass vaccination campaigns and some natural immunity within local populations. Despite this there are serious outbreaks from time to time. The Aedes mosquitoes capable of transmitting the virus from person to person, are now widespread in warmer countries worldwide, moreover they thrive in urban areas. With increased international movement, the fear is that infected travellers could unwittingly introduce the virus into countries where people have little or no immunity. Densely populated Asian megacities are a major concern. There are simple measures citizens can take to protect themselves and their homes from the bite of infected mosquitoes, but city leaders must be at the forefront of a coordinated response bringing together diverse stakeholders to ensure a robust and sustainable defence.

Background In rural sub-Saharan Africa, thatch roofs are being replaced by metal roofs. Metal roofing, however, increases indoor temperatures above human comfort levels, and thus makes it more likely that residents will not use an insecticide-treated bed net (ITN) at night. Whether the colour of a metal roof affects indoor temperature and human comfort was assessed. Methods Two identical, experimental houses were constructed with metal roofs in rural Gambia. Roof types were: (1) original bare-metal, (2) painted with red oxide primer or (3) white gloss, to reflect solar radiation. Pairwise comparisons were run in six, five-night blocks during the malaria season 2018. Indoor climate was measured in each house and multivariate analysis used to compare indoor temperatures during the day and night. Results From 21.00 to 23.59 h, when most residents decide whether to use an ITN or not, the indoor temperature of a house with a bare metal roof was 31.5 °C (95% CI 31.2–31.8 °C), a red roof, 30.3 °C (95% CI 30.0–30.6) and a white roof, 29.8 °C (95% CI 29.4–30.1). During the same period, red-roofed houses were 1.23 °C cooler (95% CI 1.22–1.23) and white roofs 1.74 °C cooler (95% CI 1.70–1.79) than bare-metal roofed houses (p p p = 0.081), compared with the bare-metal roofed houses. Human comfort analysis showed that from 21.00 to 23.59 h houses with white roofs (comfortable for 87% time) were more comfortable than bare-metal roofed houses (comfortable for 13% time; odds ratio = 43.7, 95% CI 27.5–69.5, p Conclusions Houses with a white roof were consistently cooler and more comfortable than those with a bare metal roof. Painting the roofs of houses white is a cheap way of making a dwelling more comfortable for the occupants and could potentially increase bed net use in hot humid countries.

Background: The World Health Organization recommends house screening as a tool for malaria control, yet evidence of the long-term durability, functionality and acceptability of this intervention is lacking. Here we examined the sustainability and use of novel types of screened doors and windows four years after installation in a Gambian village. Methods: A survey of 31 houses, each with two screened doors and two screened windows, was conducted in the rainy season. There were four types of screened door and two types of screened window. Trained staff carried out the survey and interviews of room owners were conducted in the local language before translation into English.Results: Structurally, the manufactured doors and windows were highly durable and in excellent condition. Most doors shut smoothly 50/61 (82%), although only 25/61 (41%) shut fully automatically with the latch slotting into the hole on the frame and holding fast. Door locks were less robust, with only (24/61) 39% present and working. Blinds proved especially flimsy, with only 4/109 (4%) of door blinds and 10/56 (18%) of window blinds present and in working order. Householders hung curtains inside most doors 50/61 (82%) and in 26/61 (43%) of the windows. Front doors were commonly found propped open 21/31 (68%) and 23/27 (85%) of those with a front door curtain, put their curtains down at night. Doors and windows were well liked, 19/31 (61%) of respondents were happy with them because they kept mosquitoes out 14/31 (45%) and provided security 12/31 (39%). The main reason given for the use of curtains was to provide privacy 26/28 (93% of those with curtains), especially while the door was open or had ‘see-through’ panels.Conclusions: Overall, the screened doors and windows were in excellent condition after four years of use. Improvements to the lock design are needed before scale-up. Installation of screening in buildings should be accompanied with health messaging recommending that at night, doors and windows be closed and curtains lifted or drawn to one side - to improve ventilation and keep the house cool.

Background The World Health Organization recommends house screening as a tool for malaria control, yet evidence of the long-term durability, functionality and acceptability of this intervention is lacking. In this study, the sustainability and use of novel types of screened doors and windows was examined 4 years after installation in a Gambian village. Methods A survey of 31 houses, each with two screened doors and two screened windows, was conducted in the rainy season. There were four types of screened door and two types of screened window. Trained staff carried out the survey and interviews of room owners were conducted in the local language before translation into English. Results Structurally, the manufactured doors and windows were highly durable and in excellent condition. Most doors shut smoothly 50/61 (82%), although only 25/61 (41%) shut fully automatically with the latch slotting into the hole on the frame and holding fast. Door locks were less robust, with only (24/61) 39% present and working. Blinds proved especially flimsy, with only 4/109 (4%) of door blinds and 10/56 (18%) of window blinds present and in working order. Householders hung curtains inside most doors 50/61 (82%) and in 26/61 (43%) of the windows. Front doors were commonly found propped open 21/31 (68%) and 23/27 (85%) of those with a front door curtain, put their curtains down at night. Doors and windows were well liked, 19/31 (61%) of respondents were happy with them because they kept mosquitoes out 14/31 (45%) and provided security 12/31 (39%). The main reason given for the use of curtains was to provide privacy 26/28 (93% of those with curtains), especially while the door was open or had ‘see-through’ panels. Conclusions Overall, the screened doors and windows were in full-working order and undamaged after 4 years of use. The doors and windows were well liked, especially for their ability to reduce the entry of mosquitoes and for the security they afforded. Improvements to the lock design are needed before scale-up. Most householders hung curtains behind their doors for privacy. Installation of screening in buildings should be accompanied with recommendations that at night, when doors and windows are closed, curtains be lifted or drawn to one side—to improve ventilation and keep the house cool.

From 2004 to 2019, insecticide-treated bednets (ITNs) have been the most effective tool for reducing malaria morbidity and mortality in sub-Saharan Africa. Recently, however, the decline in malaria cases and deaths has stalled. Some suggest that this inertia is due to increasing resistance in malaria vectors to the pyrethroid insecticides used for treating ITNs. However, there is presently little evidence to reach this conclusion and we therefore recommend that a broader perspective to evaluate ITN effectiveness in terms of access to nets, use of nets, bioefficacy, and durability should be taken. We argue that a single focus on insecticide resistance misses the bigger picture. To improve the effects of ITNs, net coverage should increase by increasing funding for programmes, adopting improved strategies for increasing ITN uptake, and enhancing the longevity of the active ingredients and the physical integrity of nets, while simultaneously accelerating the development and evaluation of novel vector control tools.

In The Gambia, metal-roof houses were hotter during the day than thatched-roof houses. After 24 h, the mortality of Anopheles gambiae, the principal African malaria vector, was 38% higher in metal-roof houses than thatched ones. During the day, mosquitoes in metal-roof houses moved from the hot roof to cooler places near the floor, where the temperature was still high, reaching 35 °C. In laboratory studies, at 35 °C few mosquitoes survived 10 days, the minimum period required for malaria parasite development. Analysis of epidemiological data showed there was less malaria and lower vector survival rates in Gambian villages with a higher proportion of metal roofs. Our findings are consistent with the hypothesis that the indoor climate of metal-roof houses, with higher temperatures and lower humidity, reduces survivorship of indoor-resting mosquitoes and may have contributed to the observed reduction in malaria burden in parts of sub-Saharan Africa.

In sub-Saharan Africa, cooler houses would increase the coverage of insecticide-treated bednets, the primary malaria control tool. We examined whether improved ventilation, using windows screened with netting, cools houses at night and reduces malaria mosquito house entry in The Gambia. Identical houses were constructed, with badly fitting doors the only mosquito entry points. Two men slept in each house and mosquitoes captured using light traps. First, temperature and mosquito density were compared in four houses with 0, 1, 2 and 3 screened windows. Second, carbon dioxide (CO2), a major mosquito attractant, was measured in houses with (i) no windows, (ii) screened windows and (iii) screened windows and screened doors. Computational fluid dynamic modelling captured the spatial movement of CO2. Increasing ventilation made houses cooler, more comfortable and reduced malaria mosquito house entry; with three windows reducing mosquito densities by 95% (95%CI = 90–98%). Screened windows and doors reduced the indoor temperature by 0.6°C (95%CI = 0.5–0.7°C), indoor CO2concentrations by 31% between 21.00 and 00.00 h and malaria mosquito entry by 76% (95%CI = 69–82%). Modelling shows screening reduces CO2plumes from houses. Under our experimental conditions, cross-ventilation not only reduced indoor temperature, but reduced the density of house-entering malaria mosquitoes, by weakening CO2plumes emanating from houses.

Most malaria infections in sub-Saharan Africa are acquired indoors, thus finding effective ways of preventing mosquito house entry should reduce transmission. Since most malaria mosquitoes fly less than 1 m from the ground, we tested whether raising buildings off the ground would prevent the entry of Anopheles gambiae , the principal African malaria vector, in rural Gambia. Nightly collections of mosquitoes were made using light traps from four inhabited experimental huts, each of which could be moved up or down. Mosquito house entry declined with increasing height, with a hut at 3 m reducing An. gambiae house entry by 84% when compared with huts on the ground. A propensity for malaria vectors to fly close to the ground and reduced levels of carbon dioxide, a major mosquito attractant, in elevated huts, may explain our findings. Raised buildings may help reduce malaria transmission in Africa.

Summary Background In malaria-endemic areas, residents of modern houses have less malaria than those living in traditional houses. We aimed to assess whether children in The Gambia received an incremental benefit from improved housing, where current best practice of insecticide-treated nets, indoor residual spraying, seasonal malaria chemoprevention in children younger than 5 years, and prompt treatment against clinical malaria was in place. Methods In this randomised controlled study, 800 households with traditional thatched-roofed houses were randomly selected from 91 villages in the Upper River Region of The Gambia. Within each village, equal numbers of houses were randomly allocated to the control and intervention groups using a sampling frame. Houses in the intervention group were modified with metal roofs and screened doors and windows, whereas houses in the control group received no modifications. In each group, clinical malaria in children aged 6 months to 13 years was monitored by active case detection over 2 years (2016–17). We did monthly collections from indoor light traps to estimate vector densities. Primary endpoints were the incidence of clinical malaria in study children with more than 50% of observations each year and household vector density. The trial is registered at ISRCTN02622179. Findings In June, 2016, 785 houses had one child each recruited into the study (398 in unmodified houses and 402 in modified houses). 26 children in unmodified houses and 28 children in modified houses did not have at least 50% of visits in a year and so were excluded from analysis. 38 children in unmodified houses were recruited after study commencement, as were 21 children in modified houses, meaning 410 children in unmodified houses and 395 in modified houses were included in the parasitological analyses. At the end of the study, 659 (94%) of 702 children were reported to have slept under an insecticide-treated net; 662 (88%) of 755 children lived in houses that received indoor residual spraying; and 151 (90%) of 168 children younger than 5 years had seasonal malaria chemoprevention. Incidence of clinical malaria was 0·12 episodes per child-year in children in the unmodified houses and 0·20 episodes per child-year in the modified houses (unadjusted incidence rate ratio [RR] 1·68 [95% CI 1·11–2·55], p=0·014). Household vector density was 3·30 Anopheles gambiae per house per night in the unmodified houses compared with 3·60 in modified houses (unadjusted RR 1·28 [0·87–1·89], p=0·21). Interpretation Improved housing did not provide protection against clinical malaria in this area of low seasonal transmission with high coverage of insecticide-treated nets, indoor residual spraying, and seasonal malaria chemoprevention. Funding Global Health Trials funded by Medical Research Council, UK Department for International Development, and Wellcome Trust.

Background: Malaria in pregnancy remains a public health problem in sub-Saharan Africa. Identifying risk factors for malaria in pregnancy could assist in developing interventions to reduce the risk of malaria in Burkina Faso and other countries in the region.Methodology: Two cross-sectional surveys were carried out to measure Plasmodium falciparum infection using microscopy in pregnant women in Saponé Health District, central Burkina Faso. Data were collected on individual, household and environmental variables and their association with P. falciparum infection assessed using multivariate analysis. Results: A total of 356 pregnant women were enrolled in the surveys, 174 during the dry season and 182 during the wet season. The mean number of doses of sulphadoxine pyrimethamine for Intermittent Preventive Treatment in pregnancy (IPTp-SP) was 0.4 doses during the first trimester, 1.1 doses at the second and 2.3 doses at the third. Overall prevalence of P. falciparum infection by microscopy was 15.7%; 17.8% in the dry season and 13.7% in the wet season. 88.2% of pregnant women reported sleeping under an insecticide-treated net on the previous night. P. falciparum infection risk in pregnancy was reduced in those women who reported using an ITN (Odds ratio, OR=0.31, 95% CI 0.12-0.79, p=0.02) and an increasing number of IPTp-SP doses during pregnancy, with each additional dose reducing the odds by 40% (OR=0.59, 95% CI 0.43–0.81, pP. falciparum infection among pregnant women remains high in Burkina Faso although use of IPTp-SP and ITNs were found to reduce the odds of infection. Despite this, compliance with IPTp remains far from that recommended by the National Malaria Control Programme and World Health Organization. Behaviour change communication should be improved to encourage compliance with protective malaria control tools during pregnancy.

In many countries, housing is used for wealth accumulation and provides financial security in old age. We tested the hypothesis that household wealth, measured by housing quality and ownership of durable assets, would increase with age of the household head.We conducted a survey of household heads in 68 villages surrounding Mtwara town, Tanzania and recorded relevant demographic, housing and social characteristics for each household. The primary analysis assessed the relationship between age of the household head, quality of the house structure and socio-economic score (SES) using multivariate analysis. Principal Components Analysis (PCA) was used as a data reduction tool to estimate the social-economic status of subjects based on relevant variables that are considered as proxy for SES.Of 13 250 household heads were surveyed of whom 49% were male. Those at least 50 years old were more likely to live in homes with an earth floor (86%) compared to younger household heads (80%; P 0.0001), wattle and daub walls (94% vs. 90%; P 0.0001) and corrugated iron roofs (56% vs. 52%; P 0.0001). Wealth accumulation in the villages included in the study tends to be an inverted V-relationship with age. Housing quality and SES rose to a peak by 50 years and then rapidly decreased. Households with a large number of members were more likely to have better housing than smaller households.Housing plays a critical role in wealth accumulation and socio-economic status of a household in rural villages in Tanzania. Households with a head under 50 years were more likely to live in improved housing and enjoyed a higher SES, than households with older heads. Larger families may provide protection against old age poverty in rural areas. Assuring financial security in old age, specifically robust and appropriate housing would have wide-ranging benefits.Dans de nombreux pays, le logement est utilisé pour l'accumulation de richesse et offre une sécurité financière à un âge avancé. Nous avons testé l'hypothèse selon laquelle la richesse des ménages, mesurée par la qualité du logement et la possession d'actifs durables, augmenterait avec l'âge du chef de ménage. MÉTHODES: Nous avons mené une enquête auprès des chefs de ménage dans 68 villages entourant la ville de Mtwara, en Tanzanie et enregistré les caractéristiques démographiques, de logement et sociales pertinentes pour chaque ménage. L'analyse primaire a évalué la relation entre l'âge du chef de ménage, la qualité de la structure du logement et le score socioéconomique (SES) à l'aide d'une analyse multivariée. L'analyse en composantes principales (ACP) a été utilisée comme outil de réduction des données pour estimer le statut socioéconomique des sujets sur la base de variables pertinentes qui sont considérées comme une approximation du SSE. RÉSULTATS: 13.250 chefs de ménage ont été interrogés, dont 49% de sexe masculin. Les personnes âgées d'au moins 50 ans étaient plus susceptibles de vivre dans des maisons avec un sol en terre (86%) que les chefs de ménage plus jeunes (80%; P0,0001), des murs en clayonnage enduit de torchis (94% contre 90%; P0,0001) et des toitures en tôle ondulée (56% contre 52%; P0,0001). L'accumulation de richesse dans les villages inclus dans l'étude a tendance à être une relation en V inversée avec l'âge. La qualité du logement et le SSE ont atteint un sommet de 50 ans, puis ont rapidement diminué. Les ménages comptant un grand nombre de membres étaient plus susceptibles d'avoir un meilleur logement que les ménages plus petits.Le logement joue un rôle essentiel dans l'accumulation de richesse et le statut socioéconomique d'un ménage dans les villages ruraux de Tanzanie. Les ménages dont le chef avait moins de 50 ans étaient plus susceptibles de vivre dans un logement amélioré et jouissaient d'un SSE plus élevé que les ménages dont le chef était plus âgé. Les familles plus nombreuses pourraient offrir une protection contre la pauvreté aux personnes âgées dans les zones rurales. Assurer la sécurité financière dans la vieillesse, en particulier un logement solide et approprié, aurait des avantages considérables.

Vector-borne diseases are a major cause of morbidity and mortality worldwide. Aedes-borne diseases, in particular, including dengue, chikungunya, yellow fever, and Zika, are increasing at an alarming rate due to urbanisation, population movement, weak vector control programmes, and climate change. The World Health Organization calls for strengthening of vector control programmes in line with the Global Vector Control Response (GVCR) strategy, and many vector control programmes are transitioning to this new approach. The Singapore dengue control programme, situated within the country’s larger vision of a clean, green, and sustainable environment for the health and well-being of its citizens, provides an excellent example of the GVCR approach in action. Since establishing vector control operations in the 1960s, the Singapore dengue control programme succeeded in reducing the dengue force of infection 10-fold by the 1990s and has maintained it at low levels ever since. Key to this success is consideration of dengue as an environmental disease, with a strong focus on source reduction and other environmental management methods as the dominant vector control strategy. The programme collaborates closely with other government ministries, as well as town councils, communities, the private sector, and academic and research institutions. Community engagement programmes encourage source reduction, and house-to-house inspections accompanied by a strong legislative framework with monetary penalties help to support compliance. Strong vector and epidemiological surveillance means that routine control activities can be heightened to specifically target dengue clusters. Despite its success, the programme continues to innovate to tackle challenges such as climate change, low herd immunity, and manpower constraints. Initiatives include development of novel vector controls such as Wolbachia-infected males and spatiotemporal models for dengue risk assessment. Lessons learnt from the Singapore programme can be applied to other settings, even those less well-resourced than Singapore, for more effective vector control., Author summary Infections due to dengue and other viruses transmitted by Aedes mosquitoes are on the rise worldwide as a result of urbanisation, trade, population movement, and climate change. Contemporary vector control programmes have struggled to control Aedes-borne diseases, but the Singapore dengue control programme provides a success story. Key to the success is consideration of dengue as an environmental disease, with a corresponding focus on removal of water containers from in and around homes, solid waste management, and limited use of insecticides. The programme relies on close collaboration with other government and nongovernment actors including communities. Community engagement campaigns to ensure high awareness are supported by house-to-house inspections for mosquito habitats and a legislative framework including penalties for noncompliance. The Singapore dengue control programme provides important lessons that can be applied to other Aedes control programmes and vector control programmes more widely.

The COVID-19 epidemic has had an unprecedented impact on the tourism sector. Trained disease detection dogs could be used for non-invasive screening at border entry points to reduce the likelihood of re-introduction of SARS-CoV-2 and limit the need for the self-isolation of all passengers.

Background Over the last two decades, there has been remarkable progress in malaria control in sub-Saharan Africa, due mainly to the massive deployment of long-lasting insecticidal nets and indoor residual spraying. Despite these gains, it is clear that in many situations, additional interventions are needed to further reduce malaria transmission. The World Health Organization (WHO) has promoted the Integrated Vector Management (IVM) approach through its Global Vector Control Response 2017–2030. However, prior roll-out of larval source management (LSM) as part of IVM, knowledge on ecology of larval aquatic habitats is required. Methods Aquatic habitats colonized by immature Anopheles and culicines vectors were characterized at three sites of low, medium and high malaria transmission in Uganda from October 2011 to June 2015. Larval surveys were conducted along transects in each site and aquatic habitats described according to type and size. Immature Anopheles, culicines and pupae from the described habitats were sampled using standard dipping methods to determine larval and pupae densities. Larvae were identified as anopheline or culicine, and counted. Pupae were not identified further. Binary logistic regression analysis was used to identify factors associated with the presence of immature Anopheles and culicines in each site. Results A total of 1205 larval aquatic habitats were surveyed and yielded a total of 17,028 anopheline larvae, 26,958 culicine larvae and 1189 pupae. Peaks in larval abundance occurred in all sites in March–May and August-October coinciding with the rainy seasons. Anopheles larvae were found in 52.4% (n = 251) of aquatic habitats in Tororo, a site of high transmission, 41.9% (n = 536) of habitats in Kanungu, a site with moderate malaria transmission, and 15.8% (n = 418) in Jinja, a site with low malaria transmission. The odds of finding larvae was highest in rice fields compared to pools in both Tororo (odds ratio, OR = 4.21, 95% CI 1.22–14.56, p = 0.02) and Kanungu (OR = 2.14, 95% CI 1.12–4.07, p = 0.02), while in Jinja the odd were highest in containers (OR = 4.55, 95% CI = 1.09–19.14, p = 0.03). In Kanungu, larvae were less likely to be found in containers compared to pools (OR = 0.26, 95% CI 0.09–0.66, p = 0.008) and river fringe (OR = 0.19, 95% CI 0.07–0.52, p = 0.001). Medium sized habitats were associated with high odds of finding larvae compared to small habitats (OR = 3.59, 95% CI 1.18–14.19, p = 0.039). Conclusions These findings show that immature Anopheles and culicines were common in areas of high and moderate transmission but were rare in areas of low transmission. Although immature Anopheles and culicines were found in all types of water bodies, they were most common in rice fields and less common in open drains and in river fringes. Methods are needed to reduce the aquatic stages of anopheline mosquitoes in human-made habitats, particularly rice fields.

Background: Over the last two decades, there has been remarkable progress in malaria control in sub-Saharan Africa, due mainly to the massive deployment of long-lasting insecticidal nets and indoor residual spraying. Despite these gains, it is clear that in many situations, additional interventions are needed to further reduce malaria transmission. Larval source management (LSM) is a potential supplementary measure that could be used to control malaria. However, prior to its roll-out, knowledge on ecology of larval aquatic habitats is required.Methods: Aquatic habitats colonized by Anopheles vectors were characterised at three sites of low, medium and high malaria transmission in Uganda from October 2011 to June 2016. Larval surveys were conducted along transects in each site and aquatic habitats described according to type and size. Anopheles mosquito larvae and pupae from the described habitats were sampled using standard dipping methods to determine larval densities. Larvae were identified as anopheline or culicine and counted. Pupae were not identified further. Binary logistic regression analysis was used to identify factors associated with the presence of Anopheles larvae in each site.Results: A total of 1,205 larval aquatic habitats were surveyed and yielded a total of 17,028 anopheline larvae, 26,958 culicine larvae and 1,189 pupae. Peaks in larval abundance occurred in all sites in March-May and August-October coinciding with the rainy seasons. Anopheles larvae were found in 52.4 % (n = 251) of aquatic habitats in Tororo, a site of high transmission, 41.9 % (n = 536) of habitats in Kanungu, a site with moderate malaria transmission, and 15.8 % (n=418) in Jinja, a site with low malaria transmission. The odds of finding Anopheles larvae was highest in rice fields compared to pools in both Tororo (odds ratio, OR = 4.21, 95% CI 1.22-14.56, p = 0.02) and Kanungu (OR= 2.14, 95% CI 1.12-4.07, p =0.02). In Kanungu, Anopheles larvae were less likely to be found in open drains compared to pools (OR = 0.15, 95% CI 0.03-0.72, p = 0.02) and river fringe (OR = 0.19, 95% CI 0.07-0.52, p = 0.001). Conclusions: These findings show that Anopheles larvae were common in areas of high and moderate transmission but were rare in areas of low transmission. Although Anopheles larvae were found in all types of water bodies, they were most common in rice fields and less common in open drains and on river fringes. Methods are needed to reduce the aquatic stages of anopheline mosquitoes in human-made habitats, particularly rice fields.

Background Housing is essential to human well-being but neglected in global health. Today, housing in Africa is rapidly improving alongside economic development, creating an urgent need to understand how these changes can benefit health. We hypothesised that improved housing is associated with better health in children living in sub-Saharan Africa (SSA). We conducted a cross-sectional analysis of housing conditions relative to a range of child health outcomes in SSA. Methods and findings Cross-sectional data were analysed for 824,694 children surveyed in 54 Demographic and Health Surveys, 21 Malaria Indicator Surveys, and two AIDS Indicator Surveys conducted in 33 countries between 2001 and 2017 that measured malaria infection by microscopy or rapid diagnostic test (RDT), diarrhoea, acute respiratory infections (ARIs), stunting, wasting, underweight, or anaemia in children aged 0–5 years. The mean age of children was 2.5 years, and 49.7% were female. Housing was categorised into a binary variable based on a United Nations definition comparing improved housing (with improved drinking water, improved sanitation, sufficient living area, and finished building materials) versus unimproved housing (all other houses). Associations between house type and child health outcomes were determined using conditional logistic regression within surveys, adjusting for prespecified covariables including age, sex, household wealth, insecticide-treated bed net use, and vaccination status. Individual survey odds ratios (ORs) were pooled using random-effects meta-analysis. Across surveys, improved housing was associated with 8%–18% lower odds of all outcomes except ARI (malaria infection by microscopy: adjusted OR [aOR] 0.88, 95% confidence intervals [CIs] 0.80–0.97, p = 0.01; malaria infection by RDT: aOR 0.82, 95% CI 0.77–0.88, p < 0.001; diarrhoea: aOR 0.92, 95% CI 0.88–0.97, p = 0.001; ARI: aOR 0.96, 95% CI 0.87–1.07, p = 0.49; stunting: aOR 0.83, 95% CI 0.77–0.88, p < 0.001; wasting: aOR 0.90, 95% CI 0.83–0.99, p = 0.03; underweight: aOR 0.85, 95% CI 0.80–0.90, p < 0.001; any anaemia: aOR 0.87, 95% CI 0.82–0.92, p < 0.001; severe anaemia: aOR 0.89, 95% CI 0.84–0.95, p < 0.001). In comparison, insecticide-treated net use was associated with 16%–17% lower odds of malaria infection (microscopy: aOR 0.83, 95% CI 0.78–0.88, p < 0.001; RDT: aOR 0.84, 95% CI 0.79–0.88, p < 0.001). Drinking water source and sanitation facility alone were not associated with diarrhoea. The main study limitations are the use of self-reported diarrhoea and ARI, as well as potential residual confounding by socioeconomic position, despite adjustments for household wealth and education. Conclusions In this study, we observed that poor housing, which includes inadequate drinking water and sanitation facility, is associated with health outcomes known to increase child mortality in SSA. Improvements to housing may be protective against a number of important childhood infectious diseases as well as poor growth outcomes, with major potential to improve children’s health and survival across SSA., In a cross-sectional analysis, Lucy S. Tusting and colleagues investigate housing conditions and child health outcomes in sub-Saharan Africa., Author summary Why was this study done? Children’s health has improved substantially in sub-Saharan Africa since 2000, but mortality among children under 5 years old is still 14 times higher than among children living in developed regions. Adequate housing is essential to human well-being but is neglected in public health. Today African housing is rapidly changing alongside economic development, presenting a major opportunity for health. However, to realise this potential, we urgently need to understand better how housing conditions affect children’s health. What did the researchers do and find? We assessed whether improved housing is associated with a lower risk of five major causes of death in African children: malaria, diarrhoea, acute respiratory infection, growth failure, and anaemia. We performed a cross-sectional analysis using data from 33 African countries collected in 77 national surveys conducted between 2001 and 2017. We analysed data from 824,694 children aged 0–5 years living in 468,471 households. Children living in housing with improved drinking water and sanitation, sufficient living area, and durable construction had a reduced likelihood of four major causes of death: malaria (12%–18% reduction), diarrhoea (8% reduction), growth failure (stunting: 17% reduction, wasting: 10% reduction, underweight: 15% reduction), and anaemia (11%–13% reduction) after accounting for differences in levels of urbanisation, poverty, vaccinations, and other public health interventions. However, there was no detectable relationship between housing conditions and acute respiratory infection. As a comparison with mainstream health interventions, children sleeping under insecticide-treated bed nets were 16%–17% less likely to be infected with malaria compared with children not sleeping under bed nets, but the quality of drinking water and sanitation alone were not associated with any reduction in diarrhoea. What do these findings mean? Improvements to housing may help to reduce the burden of disease among children in sub-Saharan Africa alongside wider poverty reduction. Housing improvements may have a similar effect on malaria to insecticide-treated bed nets. Community-level experimental studies are needed to replicate our findings in different African settings. The main limitation of this study was the use of observational data, which means that it is not possible to fully account for factors that may confound the relationship between housing and health, such as household wealth.

Background African houses are frequently too hot and uncomfortable to use a bed net at night. Indoor thermal comfort is often evaluated by measuring temperature and humidity, ignoring ventilation. This study explored ways to measure ventilation in single-roomed rural Gambian houses during the malaria transmission season and evaluated building designs that could increase airflow at night and help keep the occupants comfortable. Methods Two identical mud-walled houses were constructed with a metal roof, three doors and closed eaves. Experiment 1 compared five methods for measuring ventilation in a building: (1) using a blower door, (2) increasing carbon dioxide (CO2) levels indoors using an artificial source of CO2 and then measuring the rate of gas decay, (3) using a similar approach with a natural source of CO2, (4) measuring the rise of CO2 when people enter a building and (5) using hot-wire anemometers. Experiment 2 used CO2 data loggers to compare ventilation in a reference metal-roofed house with closed eaves and badly-fitting doors with a similar house with (1) thatched roof and open eaves, (2) eaves tubes, (3) screened doors and (4) screened doors and windows. Results In experiment 1, CO2 data loggers placed indoors in two identical houses showed similar changes in airflow (p > 0.05) for all three methods recording either decreasing or increasing CO2. Blower doors were unable to measure airflow in houses with open eaves or screened windows and the anemometers broke down under field conditions. In experiment 2, open eaves in thatched houses, screened doors alone, and screened doors and windows increased indoor ventilation compared to the reference metal-roofed house with closed eaves and badly fitting doors (p Conclusion CO2 data loggers proved to be a simple and efficient method for measuring ventilation in rural houses at night. Ventilation of metal-roofed houses can be improved by adding two screened doors and windows on opposite walls. Improved ventilation will result in increased thermal comfort making it more likely that people will sleep under a bed net.

The impact of the rapid expansion of rubber plantations in South-East Asia on mosquito populations is uncertain. We compared the abundance and diversity of adult mosquitoes using human-baited traps in four typical rural habitats in northern Lao PDR: secondary forests, immature rubber plantations, mature rubber plantations, and villages. Generalized estimating equations were used to explore differences in mosquito abundance between habitats, and Simpson’s diversity index was used to measure species diversity. Over nine months, 24,927 female mosquitoes were collected, including 51 species newly recorded in Lao PDR. A list of the 114 mosquito species identified is included. More mosquitoes, including vector species, were collected in the secondary forest than immature rubber plantations (rainy season, odds ratio [OR] 0.33, 95% confidence interval [CI] 0.31–0.36; dry season, 0.46, 95% CI 0.41–0.51), mature rubber plantations (rainy season, OR 0.25, 95% CI 0.23–0.27; dry season, OR 0.25, 95% CI 0.22–0.28), and villages (rainy season, OR 0.13, 95% CI 0.12–0.14; dry season, 0.20, 95% CI 0.18–0.23). All habitats showed high species diversity (Simpson’s indexes between 0.82–0.86) with vectors of dengue, Japanese encephalitis (JE), lymphatic filariasis, and malaria. In the secondary forests and rubber plantations, Aedes albopictus (Skuse), a dengue vector, was the dominant mosquito species, while in the villages, Culex vishnui (Theobald), a JE vector, was most common. This study has increased the overall knowledge of mosquito fauna in Lao PDR. The high abundance of Ae. albopictus in natural and man-made forests warrants concern, with vector control measures currently only implemented in cities and villages.

Vector-borne diseases (VBDs) such as malaria, dengue, and leishmaniasis exert a huge burden of morbidity and mortality worldwide, particularly affecting the poorest of the poor. The principal method by which these diseases are controlled is through vector control, which has a long and distinguished history. Vector control, to a greater extent than drugs or vaccines, has been responsible for shrinking the map of many VBDs. Here, we describe the history of vector control programmes worldwide from the late 1800s to date. Pre 1940, vector control relied on a thorough understanding of vector ecology and epidemiology, and implementation of environmental management tailored to the ecology and behaviour of local vector species. This complex understanding was replaced by a simplified dependency on a handful of insecticide-based tools, particularly for malaria control, without an adequate understanding of entomology and epidemiology and without proper monitoring and evaluation. With the rising threat from insecticide-resistant vectors, global environmental change, and the need to incorporate more vector control interventions to eliminate these diseases, we advocate for continued investment in evidence-based vector control. There is a need to return to vector control approaches based on a thorough knowledge of the determinants of pathogen transmission, which utilise a range of insecticide and non–insecticide-based approaches in a locally tailored manner for more effective and sustainable vector control., Author summary Vector-borne diseases (VBDs) such as dengue, Chagas disease, human African trypanosomiasis (HAT), leishmaniasis, and malaria exert a huge burden of morbidity and mortality worldwide. The principal method by which these diseases are controlled is through vector control. The authors chart the history of vector control through time from elucidation of the transmission route of VBDs to the present day. Pre-1940 vector control relied heavily on environmental management and larval control based on a thorough understanding of pathogen transmission but was replaced by insecticide-based vector control, often deployed as a monotherapy. The authors call for increased political will and investment in vector control and a return to locally tailored vector control that draws on the entire toolbox of interventions available.

On 21 April 1983 the Royal Society of Tropical Medicine and Hygiene held a joint meeting with the Institute of Civil Engineers at Manson House on ‘Engineering against Insect-borne Diseases in the Domestic Environment’. The summary of a talk by Chris Schofield and Graham White on ‘House design and domestic vectors of disease’ was published in a special issue of the Transactions of the Royal Society of Tropical Medicine and Hygiene.1 The manuscript highlights the home and peri-domestic environment as an important site of transmission for many vector-borne diseases, due to the presence of people, and in some cases animals, on which to feed, and provision of shelter from predators and extreme climate. For example, malaria mosquito vectors such as Anopheles gambiae readily enter houses at night to feed on humans. Aedes aegypti, the mosquito vector of diseases including dengue, yellow fever, Zika and chikungunya, is common in urban areas where water that collects in discarded plastic containers, car tires and water storage containers provides ideal aquatic habitats for this mosquito to lay its eggs. Cracked and uneven floors and walls can provide habitats for flea larvae, house dust mites, sandflies and triatomine bugs; the latter are vectors of leishmaniasis and Chagas disease, respectively. Flooded pit latrines, cracked septic tanks and stormwater drains provide habitats for Culex mosquitoes, which can transmit filariasis and contribute to nuisance biting.

Background Long-lasting insecticidal nets (LLINs) and indoor residual spraying of insecticide (IRS) are widely recommended for the prevention of malaria in endemic regions. Data from human landing catches provide information on the impact of vector control on vector populations. Here, malaria transmission indoors and outdoors, before and after mass deployment of LLINs and IRS in Uganda was compared. Methods The study took place in Tororo district, a historically high transmission area where universal LLIN distribution was conducted in November 2013 and May 2017 and 6 rounds of IRS implemented from December 2014 to July 2018. Human landing catches were performed in 8 houses monthly from October 2011 to September 2012 (pre-intervention period) and every 4 weeks from November 2017 to October 2018 (post-intervention period). Mosquitoes were collected outdoors from 18:00 to 22:00 h and indoors from 18:00 to 06:00 h. Female Anopheles were tested for the presence of Plasmodium falciparum sporozoites and species identification performed using gross dissection and polymerase chain reaction (PCR). Results The interventions were associated with a decline in human biting rate from 19.6 to 2.3 female Anopheles mosquitoes per house per night (p Anopheles gambiae sensu stricto (s.s.), which comprised an estimated 76.7% of mosquitoes. Following the interventions, the predominant species was Anopheles arabiensis, which comprised 99.5% of mosquitoes, with almost complete elimination of An. gambiae s.s. (0.5%). Conclusions Mass distribution of LLINs and 6 rounds of IRS dramatically decreased vector density and sporozoite rate resulting in a marked reduction in malaria transmission intensity in a historically high transmission site in Uganda. These changes were accompanied by a shift in vector species from An. gambiae s.s. to An. arabiensis and a relative increase in outdoor biting.

Background Long-lasting insecticidal nets (LLINs) treated with pyrethroids are the foundation of malaria control in sub-Saharan Africa. Rising pyrethroid resistance in vectors, however, has driven the development of alternative net formulations. Here the durability of polyethylene nets with a novel combination of a pyrethroid, permethrin, and the insect juvenile hormone mimic, pyriproxyfen (PPF), compared to a standard permethrin LLIN, was assessed in rural Burkina Faso. Methods A compound-randomized controlled trial was completed in two villages. In one village 326 of the PPF-permethrin nets (Olyset Duo) and 327 standard LLINs (Olyset) were distributed to assess bioefficacy. In a second village, 170 PPF-permethrin nets and 376 LLINs were distributed to assess survivorship. Nets were followed at 6-monthly intervals for 3 years. Bioefficacy was assessed by exposing permethrin-susceptible and resistant Anopheles gambiae sensu lato mosquito strains to standard World Health Organization (WHO) cone and tunnel tests with impacts on fertility measured in the resistant strain. Insecticide content was measured using high-performance liquid chromatography. LLIN survivorship was recorded with a questionnaire and assessed by comparing the physical integrity using the proportionate hole index (pHI). Results The PPF-permethrin net met WHO bioefficacy criteria (≥ 80% mortality or ≥ 95% knockdown) for the first 18 months, compared to 6 months for the standard LLIN. Mean mosquito mortality for PPF-permethrin nets, across all time points, was 8.6% (CI 2.6–14.6%) higher than the standard LLIN. Fertility rates were reduced after PPF-permethrin net exposure at 1-month post distribution, but not later. Permethrin content of both types of nets remained within the target range of 20 g/kg ± 25% for 242/248 nets tested. The pyriproxyfen content of PPF-permethrin nets declined by 54%, from 10.4 g/kg (CI 10.2–10.6) to 4.7 g/kg (CI 3.5–6.0, p Conclusion The PPF-permethrin net, Olyset Duo, met or exceeded the performance of the WHO-recommended standard LLIN (Olyset) in the current study but both net types failed the 3-year WHO bioefficacy criteria.

Lorenz von Seidlein and colleagues discuss improving house designs in rural Africa to benefit health.

Summary Background Child growth faltering persists in sub-Saharan Africa despite the scale-up of nutrition, water, and sanitation interventions over the past 2 decades. High temperatures have been hypothesised to contribute to child growth faltering via an adaptive response to heat, reduced appetite, and the energetic cost of thermoregulation. We did a cross-sectional study to assess whether child growth faltering is related to environmental temperature in sub-Saharan Africa. Methods Data were extracted from 52 Demographic and Heath Surveys, dating from 2003 to 2016, that recorded anthropometric data in children aged 0–5 years, and were linked with remotely sensed monthly mean daytime land surface temperature for 2000–16. The odds of stunting (low height-for-age), wasting (low weight-for-height), and underweight (low weight-for-age) relative to monthly mean daytime land surface temperature were determined using multivariable logistic regression. Findings The study population comprised 656 107 children resident in 373 012 households. Monthly mean daytime land surface temperature above 35°C was associated with increases in the odds of wasting (odds ratio 1·27, 95% CI 1·16–1·38; p

Approximately 150 triatomine species are suspected to be infected with the Chagas parasite, Trypanosoma cruzi, but they differ in the risk they pose to human populations. The largest risk comes from species that have a domestic life cycle and these species have been targeted by indoor residual spraying campaigns, which have been successful in many locations. It is now important to consider residual transmission that may be linked to persistent populations of dominant vectors, or to secondary or minor vectors. The aim of this project was to define the geographical distributions of the community of triatomine species across the Chagas endemic region. Presence-only data with over 12, 000 observations of triatomine vectors were extracted from a public database and target-group background data were generated to account for sampling bias in the presence data. Geostatistical regression was then applied to estimate species distributions and fine-scale distribution maps were generated for thirty triatomine vector species including those found within one or two countries and species that are more widely distributed from northern Argentina to Guatemala, Bolivia to southern Mexico, and Mexico to the southern United States of America. The results for Rhodnius pictipes, Panstrongylus geniculatus, Triatoma dimidiata, Triatoma gerstaeckeri, and Triatoma infestans are presented in detail, including model predictions and uncertainty in these predictions, and the model validation results for each of the 30 species are presented in full. The predictive maps for all species are made publicly available so that they can be used to assess the communities of vectors present within different regions of the endemic zone. The maps are presented alongside key indicators for the capacity of each species to transmit T. cruzi to humans. These indicators include infection prevalence, evidence for human blood meals, and colonisation or invasion of homes. A summary of the published evidence for these indicators shows that the majority of the 30 species mapped by this study have the potential to transmit T. cruzi to humans., Author summary The Pan American Health Organisation’s Strategy and Plan of Action for Chagas Disease Prevention, Control and Care highlights the importance of eliminating those triatomine vector species that colonise homes, and has had great success in many locations. Since indoor residual spraying campaigns have targeted these species, their importance relative to other vectors has diminished and their geographical distributions may also have changed. It is now vital to consider the full community of vector species, including previously dominant vectors as well as secondary or minor vector species, in order to target residual transmission to humans. Our aim was to define the geographical distributions of the most commonly reported triatomine species in the Chagas endemic region from northern Argentina and Chile to the southern United States of America. We extracted reports of triatomine vector species observed at specific locations from a public database and we used a geostatistical model to generate fine-scale predictive maps for thirty triatomine vector species. Data quality and data availability issues necessitate careful interpretation of the results, so (un)certainty intervals are presented alongside each map. We also present these maps alongside a summary of the published evidence for key indicators related to the capacity of each species to transmit the Chagas parasite to humans. This evidence shows that most of the 30 species that we have mapped pose a potential threat to human populations.

The putative vector of trachoma, Musca sorbens, prefers to lay its eggs on human faeces on the ground. This study sought to determine whether M. sorbens females were attracted to volatile odours from human faeces in preference to odours from the faeces of other animals, and to determine whether specific volatile semiochemicals mediate selection of the faeces. Traps baited with the faeces of humans and local domestic animals were used to catch flies at two trachoma-endemic locations in The Gambia and one in Ethiopia. At all locations, traps baited with faeces caught more female M. sorbens than control traps baited with soil, and human faeces was the most successful bait compared with soil (mean rate ratios 44.40, 61.40, 10.50 [P, Author summary Musca sorbens, also known as the Bazaar Fly, visits people’s faces to feed on ocular and nasal discharge. While feeding, M. sorbens can transmit Chlamydia trachomatis, the bacterium that causes the infectious eye disease trachoma. Around 1.9 million people worldwide are visually impaired or blind from this disease. Although it is believed that M. sorbens transmits trachoma, very few studies have looked at ways to control this fly. A large-scale trial has shown that control of fly populations with insecticide reduces active trachoma disease prevalence. Odour-baited traps for the suppression of disease vector populations are an attractive option as there is no widespread spraying of insecticide; however, highly attractive baits are critical to their success. Here, we demonstrate that the preference of these flies for breeding in human faeces is probably mediated by odour cues, and we isolate chemicals in the odour of human faeces that cause a response in the antennae of M. sorbens. These compounds may play a role in the specific attractiveness of human faeces to these flies, perhaps by being present in greater amounts or at favourable ratios. These may be developed into a chemical lure for odour-baited trapping to suppress M. sorbens populations.

Bio-Detection Dogs (BDDs) are used in some high-income countries as a diagnostic intervention, yet little is known about their potential in low/middle-income countries with limited diagnostic resources. This exploratory study investigated the opportunities and implications of deploying BDDs as a mobile diagnostic intervention to identify people with asymptomatic malaria, particularly at ports of entry, as an important step to malaria elimination in a population. A qualitative study design consisting of participant observation, five focus group discussions and informal conversations was employed in The Gambia in April–May 2017. A disciplined German Shepherd companion dog (not trained as a BDD) was introduced to research participants and their perceptions recorded. Field-notes and discussions were transcribed, translated and analysed thematically. Most research participants viewed positively the possibility of using BDDs to detect malaria, with the major advantage of being non-invasive. Some concerns, however, were raised regarding safety and efficacy, as well as cultural issues around the place of dogs within human society. The Gambia is a rabies-endemic country, and unfamiliar dogs are not usually approached, with implications for how research participants perceived BDDs. Understanding such concerns and working with local people to address such issues must be part of any successful strategy to deploy BDDs in new settings. Bio-Detection Dogs represent a potentially non-invasive diagnostic tool for the detection of asymptomatic or chronic malaria infections, particularly in areas with very low parasite rates. However, it is important to understand local concerns and work closely with communities to address those concerns. Wider deployment of BDDs will also require careful planning and sustained financial support.