Exploring the effect of house screening: are we making gains?
Authors: Emmanuel Chanda
Journal: The Lancet Planetary Health (2019)

The steady decline in global malaria burden between 2000 and 2015 averted millions of deaths via diagnosis, treatment, and vector control, but disturbingly stagnated between 2016 and 2017, as shown in the WHO World Malaria Report 2018,1WHOWorld malaria report 2018. World Health Organization, Geneva2018https://www.who.int/malaria/publications/world-malaria-report-2018/en/Date accessed: March 2, 2019Google Scholar which signals a wake-up call for response. By 2017, approximately 70% of the 219 million malaria cases were ascribed to ten African countries and India. The report also revealed an estimated additional 3·5 million cases in 2017 compared with 2016 in sub-Saharan Africa, with only 50% coverage of effective vector control in this region.1WHOWorld malaria report 2018. World Health Organization, Geneva2018https://www.who.int/malaria/publications/world-malaria-report-2018/en/Date accessed: March 2, 2019Google Scholar Notably, the suboptimal coverage and the inherent need to strengthen vector control cannot be over-emphasised. Efforts have been galvanised in the context of integrated vector management through the WHO Global Technical Strategy for Malaria 2016–30 and the Global Vector Control Response 2017–30 with an ultimate goal of implementing effective, locally adaptive, and sustainable vector control.2Chanda E Measuring the effect of insecticide resistance: are we making progress?.Lancet Infect Dis. 2018; 18: 586-588Summary Full Text Full Text PDF PubMed Scopus (4) Google Scholar Regrettably, contemporary vector control efforts are characterised by various challenges such as insecticide resistance, epidemics and emergencies, and residual transmission.3WHOGuidelines for malaria vector control. World Health Organization, Geneva2019https://apps.who.int/iris/bitstream/handle/10665/310862/9789241550499-eng.pdf?ua=1Date accessed: March 2, 2019Google Scholar Mitigation measures include resistance management strategies (ie, larval source management) and use of innovative personal protective tools with low-certainty evidence for public health value (ie, topical repellents, insecticide treated clothing, and eave tubes).3WHOGuidelines for malaria vector control. World Health Organization, Geneva2019https://apps.who.int/iris/bitstream/handle/10665/310862/9789241550499-eng.pdf?ua=1Date accessed: March 2, 2019Google Scholar Although larviciding and house screening were key vector control interventions during the preinsecticide era4Boyd MF The influence of obstacles unconsciously erected against anophelines (housing and screening) upon the incidence of malaria.Am J Trop Med. 1926; 6: 157-160Crossref Google Scholar and during the malaria eradication era,5Watson RB Maher HC An evaluation of mosquito-proofing for malaria control based on one year's observations.Am J Hyg. 1941; 34: 86-94Google Scholar they have been relegated to supplementary tools because of perceived low community-wide impact. Several empirical and operational studies have assessed effectiveness of these strategies but results have received little recognition.6Gimnig JE Slutsker L House screening for malaria control.Lancet. 2009; 374: 954-955Summary Full Text Full Text PDF PubMed Scopus (14) Google Scholar In The Lancet Planetary Health, Gerry Killeen and colleagues7Killeen GF Govella NJ Mlacha YP Chaki PP Suppression of malaria vector densities and human infection prevalence associated with scale-up of mosquito-proofed housing in Dar es Salaam, Tanzania: re-analysis of an observational series of epidemiological data.Lancet Planet Health. 2019; 3: 132-143Summary Full Text Full Text PDF PubMed Scopus (22) Google Scholar report results of a re-analysis of an observational series of epidemiological survey data in Dar es Salaam, Tanzania, on suppression of malaria vector densities and parasite prevalence by scale-up of mosquito-proofed housing.7Killeen GF Govella NJ Mlacha YP Chaki PP Suppression of malaria vector densities and human infection prevalence associated with scale-up of mosquito-proofed housing in Dar es Salaam, Tanzania: re-analysis of an observational series of epidemiological data.Lancet Planet Health. 2019; 3: 132-143Summary Full Text Full Text PDF PubMed Scopus (22) Google Scholar The findings indicated the positive correlation of an empirically fitted downward time trend in malaria prevalence and malaria vector biting densities with an upward trend in city-wide window screening coverage and progressive rollout of larviciding. Other than larviciding, no other vector-control intervention in malaria control practice was scaled up over the period of the study. Reductions in vector densities in this study were similar to those in other studies8Getawen SK Ashine T Massebo F Woldeyes D Lindtjørn B Exploring the impact of house screening intervention on entomological indices and incidence of malaria in Arba Minch town, southwest Ethiopia: a randomized control trial.Acta Trop. 2018; 181: 84-94Crossref PubMed Scopus (24) Google Scholar and attest to the potential of house screening to contribute significantly towards improvement in vector control. An earlier study in Dar es Salaam, Tanzania, provided anecdotal evidence that improved housing might be associated with decreased malaria prevalence.6Gimnig JE Slutsker L House screening for malaria control.Lancet. 2009; 374: 954-955Summary Full Text Full Text PDF PubMed Scopus (14) Google Scholar The study by Killeen and colleagues7Killeen GF Govella NJ Mlacha YP Chaki PP Suppression of malaria vector densities and human infection prevalence associated with scale-up of mosquito-proofed housing in Dar es Salaam, Tanzania: re-analysis of an observational series of epidemiological data.Lancet Planet Health. 2019; 3: 132-143Summary Full Text Full Text PDF PubMed Scopus (22) Google Scholar provides further evidence on the effectiveness of house screening. The Article presents a business case for vector control with private sector involvement through corporate social responsibility mandates. Although optimally designing and implementing house improvements remains a daunting task, house screening is potentially feasible for community deployment. Despite the availability of some guidance on supplementary interventions,3WHOGuidelines for malaria vector control. World Health Organization, Geneva2019https://apps.who.int/iris/bitstream/handle/10665/310862/9789241550499-eng.pdf?ua=1Date accessed: March 2, 2019Google Scholar key questions still need addressing. For example, what definitive role does conventional house screening play as a resistance management approach relative to innovative combinations of eave tubes and insecticides? What would be the implications of waning physical integrity of the screening materials? Given the quite high cost, what would be the sustainable modality for community-wide scale-up? What is the effect of house screening on residual transmission? Good-quality housing is a crucial factor in reducing malaria transmission across the spectrum of malaria endemicity.3WHOGuidelines for malaria vector control. World Health Organization, Geneva2019https://apps.who.int/iris/bitstream/handle/10665/310862/9789241550499-eng.pdf?ua=1Date accessed: March 2, 2019Google Scholar Killeen and colleagues'7Killeen GF Govella NJ Mlacha YP Chaki PP Suppression of malaria vector densities and human infection prevalence associated with scale-up of mosquito-proofed housing in Dar es Salaam, Tanzania: re-analysis of an observational series of epidemiological data.Lancet Planet Health. 2019; 3: 132-143Summary Full Text Full Text PDF PubMed Scopus (22) Google Scholar findings fall within the context of research efforts to provide hard evidence for the public health value of house screening. Other analyses of house screening interventions for malaria control have had promising results8Getawen SK Ashine T Massebo F Woldeyes D Lindtjørn B Exploring the impact of house screening intervention on entomological indices and incidence of malaria in Arba Minch town, southwest Ethiopia: a randomized control trial.Acta Trop. 2018; 181: 84-94Crossref PubMed Scopus (24) Google Scholar, 9Kirby MJ Ameh D Bottomley C et al.Effect of two different house screening interventions on exposure to malaria vectors and on anaemia in children in The Gambia: a randomised controlled trial.Lancet. 2009; 374: 998-1009Summary Full Text Full Text PDF PubMed Scopus (174) Google Scholar that have informed guidance on housing and health.3WHOGuidelines for malaria vector control. World Health Organization, Geneva2019https://apps.who.int/iris/bitstream/handle/10665/310862/9789241550499-eng.pdf?ua=1Date accessed: March 2, 2019Google Scholar Eave tube technology that involves house proofing with window screens combined with insecticide treated inserts10Killeen GF Masalu JP Chinula D et al.Control of malaria vector mosquitoes by insecticide-treated combinations of window screens and eave baffles.Emerg Infect Dis. 2017; 23: 782-789Crossref PubMed Scopus (34) Google Scholar has been investigated as a mitigation approach for insecticide resistance. Recognising the need to curb environmental determinants of health, larviciding and house screening are being assessed in a multicountry project in southern Africa. Acknowledging the public health risk of not having an effective insecticide-based intervention, house screening remains useful by acting as a physical barrier. Killen and colleagues7Killeen GF Govella NJ Mlacha YP Chaki PP Suppression of malaria vector densities and human infection prevalence associated with scale-up of mosquito-proofed housing in Dar es Salaam, Tanzania: re-analysis of an observational series of epidemiological data.Lancet Planet Health. 2019; 3: 132-143Summary Full Text Full Text PDF PubMed Scopus (22) Google Scholar highlight the importance of intersectoral collaboration with involvement of the private sector and operational research to develop cost-effective models for promoting and subsidising effective scale-up. House screening is a fundamental supplementary tool where core interventions have reached full scale and could potentially address the challenge of diversity and sustainability of interventions through private–public sector partnerships. I declare no competing interests. Suppression of malaria vector densities and human infection prevalence associated with scale-up of mosquito-proofed housing in Dar es Salaam, Tanzania: re-analysis of an observational series of parasitological and entomological surveysCommunity-wide mosquito proofing of houses might deliver greater impacts on vector populations and malaria transmission than previously thought. The spontaneous nature of the scale-up observed here is also encouraging with regards to practicality, acceptability, and affordability in low-income settings. Full-Text PDF Open Access