Abstract
Spatial emanators disrupt mosquito behaviour by inducing movement away from chemical stimuli and interfering with host detection and feeding. These tools were recently endorsed by the World Health Organization (WHO) for malaria control, based largely on clinical evidence from East Africa. Mosquito Shield™ is a passive, transfluthrin-based emanator designed to provide month-long protection in enclosed or semi-enclosed spaces. This study evaluated its entomological efficacy under experimental hut conditions in Benin, West Africa to generate evidence in support of WHO prequalification. An experimental hut trial was conducted against wild free-flying pyrethroid-resistant Anopheles gambiae s.l. at the Covè field station in southern Benin over two 32-day product life cycles of Mosquito Shield™. Sixteen West African–style experimental huts were assigned to Mosquito Shield™ or a placebo control. Efficacy was measured using human landing catches (HLC) and mosquito aspirations following standard hut testing methods. Primary endpoints included reductions in the numbers of mosquitoes caught through HLC (protective efficacy) and in the numbers of blood-fed mosquitoes caught through aspiration (personal protection). Secondary endpoints included deterrence, exophily, mortality, and blood-feeding inhibition. WHO susceptibility bioassays confirmed high levels of resistance to pyrethroids, including transfluthrin, in the local Anopheles gambiae s.l. population during the trial. A total of 5,682 An. gambiae s.l. and 6,158 Mansonia africana were collected through HLCs, and 1,436 An. gambiae s.l. by mosquito aspirations. Mosquito Shield™ significantly reduced mosquito landing, providing 43.0% protective efficacy (95% CI: 24.0–57.0; p < 0.001) against An. gambiae s.l. and 38.0% protective efficacy (95% CI: 12.0–57.0; p = 0.008) against Mansonia africana. Mosquito aspiration data showed 48.5% deterrence, 29.9% blood-feeding inhibition, comparable exiting rates between treatment and control huts (47.2% vs. 46.7%; p = 0.962) and 64% personal protection (95% CI: 21.9–81.8; p < 0.001) against An. gambiae s.l. No mosquito mortality was recorded in the control huts. In contrast, Mosquito Shield™ induced mortality of Anopheles gambiae s.l. reaching 49.0% in HLC collections and 22.7% in aspiration collections. Mosquito Shield™ also induced > 96% mortality in Mansonia africana, demonstrating both lethal and behavioural effects against both vector species. Overall, Mosquito Shield™ significantly reduced mosquito entry, landing, blood-feeding, and survival of pyrethroid-resistant An. gambiae s.l. under semi-field experimental hut conditions in West Africa, with additional effects against Mansonia africana. These results support its WHO prequalification and highlight its potential as a complementary vector control tool to strengthen malaria prevention and provide additional benefits for integrated control of other vector-borne diseases.
Similar content being viewed by others
Baseline malaria burden and pyrethroid resistance in Muheza, Tanzania informing a cluster randomized trial of the 3D window screens
Evaluating human landing catches as a measure of mosquito biting and the importance of considering additional modes of action
A noninferiority cluster randomised evaluation of a broflanilide indoor residual spraying insecticide, VECTRON T500, for malaria vector control in Tanzania
Data availability
The datasets generated and analysed during the current study contain information from human volunteers and are subject to ethical and regulatory restrictions. De-identified data sufficient to reproduce the analyses are available from the corresponding author upon reasonable request.
Abbreviations
- ITN:
Insecticide treated nets
- IRS:
Indoor residual spraying
- WHO:
World Health Organization
- AI:
Active ingredient
- HLC:
Human landing catches
- HBR:
Human biting rate
- IIR:
Incidence Rate Ratio
- aIIR:
adjusted Incidence Rate Ratio
- RCT:
Randomised controlled trials
- CREC:
Centre de Recherche Entomologique de Cotonou
- LSTM:
Liverpool School of Tropical Medicine
- PAMVERC:
Pan African Malaria Vector Research Consortium
- AIRID:
African Institute for Research in Infectious Diseases
References
Bhatt, S. et al. The effect of malaria control on Plasmodium falciparum in Africa between 2000 and 2015. Nature 526, 207–211 (2015).
World Health Organisation. World Malaria Report 2023. (2023).
Accrombessi, M. et al. Efficacy of pyriproxyfen-pyrethroid long-lasting insecticidal nets (LLINs) and chlorfenapyr-pyrethroid LLINs compared with pyrethroid-only LLINs for malaria control in Benin: a cluster-randomised, superiority trial. Lancet 401, 435–446 (2023).
Mosha, J. F. et al. Effectiveness and cost-effectiveness against malaria of three types of dual-active-ingredient long-lasting insecticidal nets (LLINs) compared with pyrethroid-only LLINs in Tanzania: a four-arm, cluster-randomised trial. Lancet 399, 1227–1241 (2022).
Accrombessi, M. et al. Effectiveness of pyriproxyfen-pyrethroid and chlorfenapyr-pyrethroid long-lasting insecticidal nets (LLINs) compared with pyrethroid-only LLINs for malaria control in the third year post-distribution: a secondary analysis of a cluster-randomised controlled trial in Benin (The Lancet Infectious Diseases, 2024).
Ngufor, C. et al. The attrition, physical and insecticidal durability of two dual active ingredient nets (Interceptor® G2 and Royal Guard®) in Benin, West Africa: results from a durability study embedded in a cluster randomised controlled trial. Parasit. Vectors. 17, 420 (2024).
Chen, I. et al. Volatile pyrethroid spatial repellents for preventing mosquito bites: a systematic review and meta-analysis. eBioMedicine 119. (2025).
Ochomo, E. O. et al. Effect of a spatial repellent on malaria incidence in an area of western Kenya characterised by high malaria transmission, insecticide resistance, and universal coverage of insecticide treated nets (part of the AEGIS Consortium): a cluster-randomised, controlled trial. Lancet 405, 147–156 (2025).
Hill, N. et al. A household randomized, controlled trial of the efficacy of 0.03% transfluthrin coils alone and in combination with long-lasting insecticidal nets on the incidence of Plasmodium falciparum and Plasmodium vivax malaria in Western Yunnan Province, China. Malar. J. 13, 208 (2014).
Syafruddin, D. et al. Efficacy of a spatial repellent for control of malaria in Indonesia: a cluster-randomized controlled trial. Am. J. Trop. Med. Hyg. 103, 344 (2020).
WHO. WHO recommends spatial emanators for malaria vector control and prequalifies first two products. World Health Organisation (2025). https://www.who.int/news/item/13-08-2025-who-recommends-spatial-emanators-for-malaria-vector-control-and-prequalifies-first-two-products
World Health Organisation. Guidelines for malaria (World Health Organisation, 2025). https://iris.who.int/bitstream/handle/10665/382254/B09514-eng.pdf?sequence=1
Fongnikin, A. et al. Mosquito Shield™, a transfluthrin passive emanator, protects against pyrethroid-resistant Anopheles gambiae sensu lato in central Benin. Malar. J. 23, 225 (2024).
Syme, T. et al. PermaNet Dual, a new deltamethrin-chlorfenapyr mixture net, shows improved efficacy against pyrethroid-resistant Anopheles gambiae sensu lato in southern Benin. Sci. Rep. 13, 12232 (2023).
Ngufor, C. et al. Insecticide resistance profile of Anopheles gambiae from a phase II field station in Cove, southern Benin: implications for the evaluation of novel vector control products. Malar. J. 14, 464 (2015).
WHO Prequalification of Vector Control Products. WHO Guideline for the Prequalification Assessment of Insecticide-Treated Nets (World Health Organisation, 2023).
WHO: Standard operating procedure for testing insecticide susceptibility of adult mosquitoes in WHO bottle bioassays, WHO Bottle-bioassay/01/14 January 2022. World Health Organisation, Geneva. (2022). https://apps.who.int/iris/handle/10665/352312?search-result=true&query=WHO+bottle+bioassay&scope=&rpp=10&sort_by=scoreℴ=desc
WHO: Manual for monitoring insecticide resistance in mosquito vectors and selecting appropriate interventions. World Health Organisation, Geneva. (2022). https://www.who.int/publications/i/item/9789240051089
Swai, J. K. et al. Efficacy of the spatial repellent product Mosquito Shield™ against wild pyrethroid-resistant Anopheles arabiensis in south-eastern Tanzania. Malar. J. 22, 249 (2023).
N’Guessan, R., Corbel, V., Akogbeto, M. & Rowland, M. Reduced efficacy of insecticide-treated nets and indoor residual spraying for malaria control in pyrethroid resistance area, Benin. Emerg. Infect. Dis. 13, 199–206 (2007).
Sarrassat, S. et al. High exposure to malaria vector bites despite high use of bednets in a setting of seasonal malaria in southwestern Mali: the urgent need for outdoor vector control strategies. Parasites Vectors. 18, 274 (2025).
Ngufor, C. et al. Comparative efficacy of two pyrethroid-piperonyl butoxide nets (Olyset Plus and PermaNet 3.0) against pyrethroid resistant malaria vectors: a non-inferiority assessment. Malar. J. 21, 20 (2022).
Syme, T. et al. Pyrethroid-piperonyl butoxide (PBO) nets reduce the efficacy of indoor residual spraying with pirimiphos-methyl against pyrethroid-resistant malaria vectors. Sci. Rep. 12, 6857 (2022).
Nounagnon, J. et al. Efficacy of Vector Guard®, a mosaic alpha-cypermethrin and piperonyl butoxide-treated net, for the control of pyrethroid-resistant malaria vectors: a non-inferiority experimental hut evaluation in Benin. Parasites Vectors. 18, 397 (2025).
Ughasi, J. et al. Mansonia africana and Mansonia uniformis are Vectors in the transmission of Wuchereria bancrofti lymphatic filariasis in Ghana. Parasites Vectors. 5, 89 (2012).
Ogoma, S. B. et al. A low technology emanator treated with the volatile pyrethroid transfluthrin confers long term protection against outdoor biting vectors of lymphatic filariasis, arboviruses and malaria. PLoS Negl. Trop. Dis. 11, e0005455 (2017).
Swai, J. K. et al. Efficacy of the spatial repellent SC Johnson Mosquito Shield™ against anophelines in free-flight chambers, semi-field systems, experimental huts, and in-home tests. Frontiers Malaria Volume 3–2025. (2025).
Tambwe, M. M. et al. Human landing catches provide a useful measure of protective efficacy for the evaluation of volatile pyrethroid spatial repellents. Parasites Vectors. 16, 90 (2023).
Jamrozik, E., de la Fuente-Núñez, V., Reis, A., Ringwald, P. & Selgelid, M. J. Ethical aspects of malaria control and research. Malar. J. 14, 518 (2015).
WHO. WHO Implementation guidance: semi-field studies for spatial emanator products. World Health Organisation (2025). https://extranet.who.int/prequal/sites/default/files/document_files/IG_SE_Semi-field_studies_v0_Aug_2025_0.pdf
WHO: List of WHO prequalified vector control products. Geneva, Switzerland: World Health Organization. (2025). https://www.who.int/pq-vector-control/prequalified-lists/PrequalifiedProducts27January2020.pdf?ua=1
Acknowledgements
We thank Dr. Thomas Mascari and Mrs. Madeleine Conaway of SC Johnson & Son, Inc. for providing the test items and their valuable support. We are grateful to the rice farmers of Cové for their participation and collaboration, and to the staff of the CREC/AIRID/PAMVERC-Benin Research Programme (including Imelda Glele, Apithy Danielle, Nadia Houeto, Damien Todjinou, and others) for their dedicated assistance throughout the study.
Funding
This work was funded through a research grant awarded to Corine Ngufor by SC Johnson & Son Inc. The funder had no role in the study design, data collection or analysis, manuscript preparation, or the decision to publish.
Author information
Authors and Affiliations
Contributions
CN acquired funding, designed the study and supervised its implementation. BN, JA and MY performed the hut trial with support from TS. TS, BN and CN analysed the data and prepared the manuscript tables and figures. CN and BN wrote the manuscript text with support from TS, BP and AY. All authors read and approved the final manuscript.
Corresponding author
Ethics declarations
Competing interests
The authors declare no competing interests.
Additional information
Publisher’s note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Rights and permissions
Open Access This article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which permits any non-commercial use, sharing, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if you modified the licensed material. You do not have permission under this licence to share adapted material derived from this article or parts of it. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by-nc-nd/4.0/.
Reprints and permissions
About this article
Cite this article
N’dombidjé, B., Syme, T., Ahoga, J. et al. Experimental hut evaluation of mosquito shield, a transfluthrin spatial emanator, for control of wild pyrethroid resistant malaria vectors in Benin.
Sci Rep (2026). https://doi.org/10.1038/s41598-026-48240-9
Received:
Accepted:
Published:
DOI: https://doi.org/10.1038/s41598-026-48240-9
Keywords
- Spatial emanators
- Mosquito Shield
- West African experimental huts
- Benin
- Transfluthrin
- Anopheles gambiae sensu lato
- integrated vector control
Source: Ecology - nature.com
