Published in PLOS One on 2026-07-30, this study is presented as an attributed evidence briefing. The excerpts below are the original researchers’ words, reproduced under their Creative Commons Attribution licence. Health Signal has selected the abstract and, where needed, opening background paragraphs; the complete methods, results, limitations and references remain in the linked paper.
Original authors: Joaquim Domingos Lequechane, Luís Filipe Lopes, Luzia Gonçalves, Nicole Azevedo, Ana Paula Abílio, Ana Bernardo Duajá, João Luís Manuel, Henrique Silveira
Source: PLOS One • DOI 10.1371/journal.pone.0353351
Read the complete primary study ↗ · Creative Commons Attribution licence
From the researchers
Abstract
Malaria remains a major public health challenge in sub-Saharan Africa. Increasing mosquito resistance to insecticides can significantly limit current vector control strategies. Spatial repellents represent a promising complementary tool by disrupting mosquito human-seeking behaviour. This trial aimed to evaluate the efficacy of IR3535 as a spatial repellent in Tambai, a high-transmission rural area in central Mozambique.
This was a randomised, Before-After-Control-Intervention trial. Four Tambai blocks were randomly selected, with 40 households randomly assigned to receive IR3535 spraying and 40 assigned to as a no-repellent control group. Plasmodium falciparum malaria prevalence was estimated in children under 5 years of age using polymerase chain reaction, before, at year one and at year two. Data were first analysed using frequentist methods and subsequently using spatiotemporal Bayesian models, incorporating INLA-based models to assess the impact of repellent intervention on mosquito density and diversity, sporozoite rates, and malaria prevalence in the repellent and control groups.
A total of 5716 mosquitoes were collected, 57.2% were Anopheles and 42.7% were Culex sp.. An. funestus s.l. females, were the most prevalent mosquito both indoor (92.7%) and outdoor (82.5%), followed by An. gambiae and An. tenebrosus. The total number of An. funestus s.l. females was lower in the repellent group compared with the control group [indoors: 765 vs 1,432; outdoors: 175 vs 293], as was the average number of mosquitoes collected per household [indoors: 18.6 vs 35.0; outdoors: 4.3 vs 7.1]. Spatiotemporal analysis revealed evidence of repellent-associated reduction in mosquito densities, with species-specific and indoor-outdoor differences, highlighting An. funestus s.l. dominance and spatial-temporal clustering patterns. P. falciparum prevalence among children under five declined from 72.6% (95% CI = 64.1–80.2) at baseline to 51.3% (95% CI = 43.5–59.1) at year one and 43.3% (95% CI = 35.7–51.1) at the end of the study, with similar reductions in both repellent and control groups. Sporozoite rates were slightly lower in the repellent group, particularly outdoors, however, these differences could not be directedly attributed to the repellent.
Our findings indicate that the use of IR3535 as a spatial repellent reduces indoor and outdoor malaria vector densities, which may contribute to reduced malaria transmission.
ClinicalTrials.gov NCT04419766
Introduction
Malaria is a preventable and curable disease, nevertheless, its control and elimination remain a global challenge, particularly in sub-Saharan Africa. An estimate of 282 million cases and 610 000 deaths occurred in 2024 worldwide, with WHO African region being the most affected, accounting almost 94% of cases and 95% of malaria deaths, Mozambique being the fifth and seventh country with highest malaria cases and deaths, respectively [1]. Insecticide-treated bed nets (ITN) and indoor residual spraying (IRS) have been the main strategies for controlling the disease and have significantly reduced malaria cases and deaths from 2000 to 2015 [2]. However, the emergence of vector resistance to insecticides, combined with decreasing budgets for malaria programmes, could compromise the elimination of the disease. Additionally, ITN and IRS primarily target indoor adult mosquitos leaving residual transmission a persistent concern. This gap can be addressed by combining current control tools with innovative approaches, such as the use of spatial repellent, to achieve malaria control and its elimination by 2030 [3].
Reading this evidence
Use the full paper to check the study design, participant selection, comparator and outcome definitions before drawing a practical conclusion. An association does not by itself show cause and effect. A reported performance measure needs its denominator and uncertainty. A finding from a particular facility, sample or time period should retain that scope when it is discussed elsewhere.
This briefing makes the source accessible within the wider public health desk. It does not assess an individual patient or certify a product. When considering relevance to another health system, examine the original authors’ account of context and limitations, then seek local implementation evidence. The related reporting below provides other studies to read alongside this one; it is a topic connection, rather than a claim that their results are directly comparable.
© 2026 Joaquim Domingos Lequechane, Luís Filipe Lopes, Luzia Gonçalves, Nicole Azevedo, Ana Paula Abílio, Ana Bernardo Duajá, João Luís Manuel, Henrique Silveira. Excerpts reproduced under CC BY. Selection, formatting and contextual notes by Health Signal. The researchers are the authors of the source study, not members of Health Signal’s staff.
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