Housing interventions for preventing malaria

Community perceptions, acceptability, and the durability of house screening interventions against exposure to malaria vectors in Nyimba district, Zambia

BACKGROUND

House screening remains conspicuously absent in national malaria programs despite its recognition by the World Health Organization as a supplementary malaria vector-control intervention. This may be attributed, in part, to the knowledge gap in screen durability or longevity in local climatic conditions and community acceptance under specific cultural practices and socio-economic contexts. The objectives of this study were to assess the durability of window and door wire mesh screens a year after full house screening and to assess the acceptability of the house screening intervention to the participants involved.

METHODS

This study was conducted in Nyimba district, Zambia and used both quantitative and qualitative methods of data collection and analysis. Both direct observation and questionnaires were employed to assess the durability of the screens and the main reasons for damage. Findings on damage were summarized as percentages. Focus group discussions were used to assess people's knowledge, perceptions, and acceptability of the closing eaves and house screening intervention. Deductive coding and inductive coding were used to analyse the qualitative data.

RESULTS

A total of 321 out of 400 (80.3%) household owners of screened houses were interviewed. Many window screens (90.3%) were intact. In sharp contrast, most door screens were torn (n = 150; 46.7%) or entirely removed (n = 55; 17.1%). Most doors (n = 114; 76%) had their wire mesh damaged or removed on the bottom half. Goats (25.4%), rust (17.6%) and children (17.1%) were cited most as the cause of damage to door screens. The focus group discussion elicited positive experiences from the participants following the closing of eaves and screening of their windows and doors, ranging from sleeping peacefully due to reduced mosquito biting and/or nuisance and having fewer insects in the house. Participants linked house screening to reduced malaria in their households and community.

CONCLUSION

This study demonstrated that in rural south-east Zambia, closing eaves and screening windows and doors was widely accepted. Participants perceived that house screening reduced human-vector contact, reduced the malaria burden and nuisance biting from other potentially disease carrying insects. However, screened doors are prone to damage, mainly by children, domestic animals, rust, and termites.

House modifications for preventing malaria

BACKGROUND

Malaria remains an important public health problem. Research in 1900 suggested house modifications may reduce malaria transmission. A previous version of this review concluded that house screening may be effective in reducing malaria. This update includes data from five new studies.

OBJECTIVES

To assess the effects of house modifications that aim to reduce exposure to mosquitoes on malaria disease and transmission.

SEARCH METHODS

We searched the Cochrane Infectious Diseases Group Specialized Register; Central Register of Controlled Trials (CENTRAL), published in the Cochrane Library; MEDLINE (PubMed); Embase (OVID); Centre for Agriculture and Bioscience International (CAB) Abstracts (Web of Science); and the Latin American and Caribbean Health Science Information database (LILACS) up to 25 May 2022. We also searched the World Health Organization International Clinical Trials Registry Platform, ClinicalTrials.gov, and the ISRCTN registry to identify ongoing trials up to 25 May 2022.

SELECTION CRITERIA

Randomized controlled trials, including cluster-randomized controlled trials (cRCTs), cross-over studies, and stepped-wedge designs were eligible, as were quasi-experimental trials, including controlled before-and-after studies, controlled interrupted time series, and non-randomized cross-over studies. We sought studies investigating primary construction and house modifications to existing homes reporting epidemiological outcomes (malaria case incidence, malaria infection incidence or parasite prevalence). We extracted any entomological outcomes that were also reported in these studies.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected eligible studies, extracted data, and assessed the risk of bias. We used risk ratios (RR) to compare the effect of the intervention with the control for dichotomous data. For continuous data, we presented the mean difference; and for count and rate data, we used rate ratios. We presented all results with 95% confidence intervals (CIs). We assessed the certainty of evidence using the GRADE approach.

MAIN RESULTS

One RCT and six cRCTs met our inclusion criteria, with an additional six ongoing RCTs. We did not identify any eligible non-randomized studies. All included trials were conducted in sub-Saharan Africa since 2009; two randomized by household and four at the block or village level. All trials assessed screening of windows, doors, eaves, ceilings, or any combination of these; this was either alone, or in combination with roof modification or eave tube installation (an insecticidal "lure and kill" device that reduces mosquito entry whilst maintaining some airflow). In one trial, the screening material was treated with 2% permethrin insecticide. In five trials, the researchers implemented the interventions. A community-based approach was adopted in the other trial. Overall, the implementation of house modifications probably reduced malaria parasite prevalence (RR 0.68, 95% CI 0.57 to 0.82; 5 trials, 5183 participants; moderate-certainty evidence), although an inconsistent effect was observed in a subpopulation of children in one study. House modifications reduced moderate to severe anaemia prevalence (RR 0.70, 95% CI 0.55 to 0.89; 3 trials, 3643 participants; high-certainty evidence). There was no consistent effect on clinical malaria incidence, with rate ratios ranging from 0.38 to 1.62 (3 trials, 3365 participants, 4126.6 person-years). House modifications may reduce indoor mosquito density (rate ratio 0.63, 95% CI 0.30 to 1.30; 4 trials, 9894 household-nights; low-certainty evidence), although two studies showed little effect on this parameter.

AUTHORS' CONCLUSIONS

House modifications - largely screening, sometimes combined with insecticide and lure and kill devices - were associated with a reduction in malaria parasite prevalence and a reduction in people with anaemia. Findings on malaria incidence were mixed. Modifications were also associated with lower indoor adult mosquito density, but this effect was not present in some studies.

A review of the impact of shelter design on the health of displaced populations

There are currently millions of displaced people encamped in low-quality shelters that jeopardise the health of these displaced populations. These shelters, which exhibit poor thermal regulation and air quality, are often inhabited by households for several years. Recently, the internal environment of shelters has been recognised as a determinant of the health of the occupants and the indoor air quality (IAQ) and internal temperatures have been identified as critical factors affecting occupants' health. Attempts by researchers and private companies to develop healthier shelter solutions have mainly prioritised factors such as rapid deployment, transportability and sustainability. Via a systematic bibliometric analysis of the existing literature, this review examines the impact of shelters' internal environment on occupant health. Self-reports and building simulation are the most common methodologies reported in the literature, but there is a disconnect between the reported shelter issues and their impact on health. This is likely due to the multifaceted and site-specific factors analysed. Indoor air quality, thermal comfort and overcrowding are the most commonly identified shelter issues, which are strongly related to the presence of infectious and airborne diseases. An analysis of the available literature indicates that there is still a lack of clear guidance linking shelter quality to health. Moreover, evidence of the impact of shelters on health is harder to find, and there is a gap regarding the metrics and the methodology used to evaluate shelter quality. Therefore, further research is necessary to provide evidence of the impact of shelter design on health through transdisciplinary approaches.

Vector control for malaria prevention during humanitarian emergencies: protocol for a systematic review and meta-analysis

INTRODUCTION

Humanitarian emergencies, of either natural or anthropogenic origins, are equivalent to major disasters, which can lead to population displacement, food insecurity and health system disruptions. Almost two-thirds of people affected by humanitarian emergencies inhabit malaria endemic regions, particularly the WHO African Region, which currently accounts for 93% and 94% of malaria cases and deaths, respectively. As of late 2020, the United Nations Refugee Agency estimates that there are globally 79.5 million forcibly displaced people, including 45.7 million internally displaced people, 26 million refugees, 4.2 million asylum-seekers and 3.6 million Venezuelans displaced abroad.

METHODS AND ANALYSES

A systematic review and meta-analysis will be conducted to evaluate the impact of different vector control interventions on malaria disease burden during humanitarian emergencies. Published and grey literatures will be systematically retrieved from 10 electronic databases and 3 clinical trials registries. A systematic approach to screening, reviewing and data extraction will be applied based on the Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines. Two review authors will independently assess full-text copies of potentially relevant articles based on inclusion criteria. Included studies will be assessed for risk of bias according to Cochrane and certainty of evidence using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach. Eligible studies with reported or measurable risk ratios or ORs with 95% CIs will be included in a meta-analysis. Subgroup analyses, including per study design, emergency phase and primary mode of intervention, may be performed if substantial heterogeneity is encountered.

ETHICS AND DISSEMINATION

Ethical approval is not required by the London School of Hygiene and Tropical Medicine to perform secondary analyses of existing anonymous data. Study findings will be disseminated via open-access publications in peer-reviewed journals, presentations to stakeholders and international policy makers, and will contribute to the latest WHO guidelines for malaria control during humanitarian emergencies.

PROSPERO REGISTRATION NUMBER

CRD42020214961.

House modifications for preventing malaria

BACKGROUND

Despite being preventable, malaria remains an important public health problem. The World Health Organization (WHO) reports that overall progress in malaria control has plateaued for the first time since the turn of the century. Researchers and policymakers are therefore exploring alternative and supplementary malaria vector control tools. Research in 1900 indicated that modification of houses may be effective in reducing malaria: this is now being revisited, with new research now examining blocking house mosquito entry points or modifying house construction materials to reduce exposure of inhabitants to infectious bites.

OBJECTIVES

To assess the effects of house modifications on malaria disease and transmission.

SEARCH METHODS

We searched the Cochrane Infectious Diseases Group Specialized Register; Central Register of Controlled Trials (CENTRAL), published in the Cochrane Library; MEDLINE (PubMed); Embase (OVID); Centre for Agriculture and Bioscience International (CAB) Abstracts (Web of Science); and the Latin American and Caribbean Health Science Information database (LILACS), up to 1 November 2019. We also searched the WHO International Clinical Trials Registry Platform (www.who.int/ictrp/search/en/), ClinicalTrials.gov (www.clinicaltrials.gov), and the ISRCTN registry (www.isrctn.com/) to identify ongoing trials up to the same date.

SELECTION CRITERIA

Randomized controlled trials, including cluster-randomized controlled trials (cRCTs), cross-over studies, and stepped-wedge designs were eligible, as were quasi-experimental trials, including controlled before-and-after studies, controlled interrupted time series, and non-randomized cross-over studies. We only considered studies reporting epidemiological outcomes (malaria case incidence, malaria infection incidence or parasite prevalence). We also summarised qualitative studies conducted alongside included studies.

DATA COLLECTION AND ANALYSIS

Two review authors selected eligible studies, extracted data, and assessed the risk of bias. We used risk ratios (RR) to compare the effect of the intervention with the control for dichotomous data. For continuous data, we presented the mean difference; and for count and rate data, we used rate ratios. We presented all results with 95% confidence intervals (CIs). We assessed the certainty of evidence using the GRADE approach.

MAIN RESULTS

Six cRCTs met our inclusion criteria, all conducted in sub-Saharan Africa; three randomized by household, two by village, and one at the community level. All trials assessed screening of windows, doors, eaves, ceilings or any combination of these; this was either alone, or in combination with eave closure, roof modification or eave tube installation (a "lure and kill" device that reduces mosquito entry whilst maintaining some airflow). In two trials, the interventions were insecticide-based. In five trials, the researchers implemented the interventions. The community implemented the interventions in the sixth trial. At the time of writing the review, two of the six trials had published results, both of which compared screened houses (without insecticide) to unscreened houses. One trial in Ethiopia assessed screening of windows and doors. Another trial in the Gambia assessed full screening (screening of eaves, doors and windows), as well as screening of ceilings only. Screening may reduce clinical malaria incidence caused by Plasmodium falciparum (rate ratio 0.38, 95% CI 0.18 to 0.82; 1 trial, 184 participants, 219.3 person-years; low-certainty evidence; Ethiopian study). For malaria parasite prevalence, the point estimate, derived from The Gambia study, was smaller (RR 0.84, 95% CI 0.60 to 1.17; 713 participants, 1 trial; low-certainty evidence), and showed an effect on anaemia (RR 0.61, 95% CI 0.42, 0.89; 705 participants; 1 trial, moderate-certainty evidence). Screening may reduce the entomological inoculation rate (EIR): both trials showed lower estimates in the intervention arm. In the Gambian trial, there was a mean difference in EIR between the control houses and treatment houses ranging from 0.45 to 1.50 (CIs ranged from -0.46 to 2.41; low-certainty evidence), depending on the study year and treatment arm. The Ethiopian trial reported a mean difference in EIR of 4.57, favouring screening (95% CI 3.81 to 5.33; low-certainty evidence). Pooled analysis of the trials showed that individuals living in fully screened houses were slightly less likely to sleep under a bed net (RR 0.84, 95% CI 0.65 to 1.09; 2 trials, 203 participants). In one trial, bed net usage was also lower in individuals living in houses with screened ceilings (RR 0.69, 95% CI 0.50 to 0.95; 1 trial, 135 participants).

AUTHORS' CONCLUSIONS

Based on the two trials published to date, there is some evidence that screening may reduce malaria transmission and malaria infection in people living in the house. The four trials awaiting publication are likely to enrich the current evidence base, and we will add these to this review when they become available.

House modifications for preventing malaria

BACKGROUND

Despite being preventable, malaria remains an important public health problem. The World Health Organization (WHO) reports that overall progress in malaria control has plateaued for the first time since the turn of the century. Researchers and policymakers are therefore exploring alternative and supplementary malaria vector control tools. Research in 1900 indicated that modification of houses may be effective in reducing malaria: this is now being revisited, with new research now examining blocking house mosquito entry points or modifying house construction materials to reduce exposure of inhabitants to infectious bites.

OBJECTIVES

To assess the effects of house modifications on malaria disease and transmission.

SEARCH METHODS

We searched the Cochrane Infectious Diseases Group Specialized Register; Central Register of Controlled Trials (CENTRAL), published in the Cochrane Library; MEDLINE (PubMed); Embase (OVID); Centre for Agriculture and Bioscience International (CAB) Abstracts (Web of Science); and the Latin American and Caribbean Health Science Information database (LILACS), up to 1 November 2019. We also searched the WHO International Clinical Trials Registry Platform (www.who.int/ictrp/search/en/), ClinicalTrials.gov (www.clinicaltrials.gov), and the ISRCTN registry (www.isrctn.com/) to identify ongoing trials up to the same date.

SELECTION CRITERIA

Randomized controlled trials, including cluster-randomized controlled trials (cRCTs), cross-over studies, and stepped-wedge designs were eligible, as were quasi-experimental trials, including controlled before-and-after studies, controlled interrupted time series, and non-randomized cross-over studies. We only considered studies reporting epidemiological outcomes (malaria case incidence, malaria infection incidence or parasite prevalence). We also summarised qualitative studies conducted alongside included studies.

DATA COLLECTION AND ANALYSIS

Two review authors selected eligible studies, extracted data, and assessed the risk of bias. We used risk ratios (RR) to compare the effect of the intervention with the control for dichotomous data. For continuous data, we presented the mean difference; and for count and rate data, we used rate ratios. We presented all results with 95% confidence intervals (CIs). We assessed the certainty of evidence using the GRADE approach.

MAIN RESULTS

Six cRCTs met our inclusion criteria, all conducted in sub-Saharan Africa; three randomized by household, two by village, and one at the community level. All trials assessed screening of windows, doors, eaves, ceilings or any combination of these; this was either alone, or in combination with eave closure, roof modification or eave tube installation (a "lure and kill" device that reduces mosquito entry whilst maintaining some airflow). In two trials, the interventions were insecticide-based. In five trials, the researchers implemented the interventions. The community implemented the interventions in the sixth trial. At the time of writing the review, two of the six trials had published results, both of which compared screened houses (without insecticide) to unscreened houses. One trial in Ethiopia assessed screening of windows and doors. Another trial in the Gambia assessed full screening (screening of eaves, doors and windows), as well as screening of ceilings only. Screening may reduce clinical malaria incidence caused by Plasmodium falciparum (rate ratio 0.38, 95% CI 0.18 to 0.82; 1 trial, 184 participants, 219.3 person-years; low-certainty evidence; Ethiopian study). For malaria parasite prevalence, the point estimate, derived from The Gambia study, was smaller (RR 0.84, 95% CI 0.60 to 1.17; 713 participants, 1 trial; moderate-certainty evidence), and showed an effect on anaemia (RR 0.61, 95% CI 0.42, 0.89; 705 participants; 1 trial, moderate-certainty evidence). Screening may reduce the entomological inoculation rate (EIR): both trials showed lower estimates in the intervention arm. In the Gambian trial, there was a mean difference in EIR between the control houses and treatment houses ranging from 0.45 to 1.50 (CIs ranged from -0.46 to 2.41; low-certainty evidence), depending on the study year and treatment arm. The Ethiopian trial reported a mean difference in EIR of 4.57, favouring screening (95% CI 3.81 to 5.33; low-certainty evidence). Pooled analysis of the trials showed that individuals living in fully screened houses were slightly less likely to sleep under a bed net (RR 0.84, 95% CI 0.65 to 1.09; 2 trials, 203 participants). In one trial, bed net usage was also lower in individuals living in houses with screened ceilings (RR 0.69, 95% CI 0.50 to 0.95; 1 trial, 135 participants).

AUTHORS' CONCLUSIONS

Based on the two trials published to date, there is some evidence that screening may reduce malaria transmission and malaria infection in people living in the house. The four trials awaiting publication are likely to enrich the current evidence base, and we will add these to this review when they become available.