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Randomized Controlled Trial
. 2022 Jun 3;21(1):166.
doi: 10.1186/s12936-022-04185-8.

Impact of a spatial repellent product on Anopheles and non-Anopheles mosquitoes in Sumba, Indonesia

Dendi H Permana #  1 , Siti Zubaidah #  1 , Lepa Syahrani #  1 , Puji B S Asih  1 , Din Syafruddin  2   3 , Ismail E Rozi  1 , Anggi P N Hidayati  1 , Sully Kosasih  1 , Farahana K Dewayanti  1 , Nia Rachmawati  1 , Rifqi Risandi  1 , Michael J Bangs  4   5 , Claus Bøgh  6 , Jenna R Davidson  7 , Allison L Hendershot  7 , Timothy A Burton  7 , John P Grieco  7 , Evercita C Eugenio  8 , Fang Liu  9 , Nicole L Achee  7 , Neil F Lobo  7
Affiliations
Randomized Controlled Trial

Impact of a spatial repellent product on Anopheles and non-Anopheles mosquitoes in Sumba, Indonesia

Dendi H Permana et al. Malar J. .

Abstract

Background: The East Nusa Tenggara province, Indonesia, contributed to 5% of malaria cases nationally in 2020, with other mosquito-borne diseases, such as dengue and filariasis also being endemic. Monitoring of spatial and temporal vector species compositions and bionomic traits is an efficient method for generating evidence towards intervention strategy optimization and meeting disease elimination goals.

Methods: The impact of a spatial repellent (SR) on human biting mosquitoes was evaluated as part of a parent cluster-randomized, double-blinded, placebo-controlled trial, in Sumba, East Nusa Tenggara. A 10-month (June 2015-March 2016) baseline study was followed by a 24-month intervention period (April 2016 to April 2018)-where half the clusters were randomly assigned either a passive transfluthrin emanator or a placebo control.

Results: Human-landing mosquito catches documented a reduction in landing rates related to the SR. Overall, there was a 16.4% reduction (21% indoors, and 11.3% outdoors) in human biting rates (HBR) for Anopheles. For Aedes, there was a 44.3% HBR reduction indoors and a 35.6% reduction outdoors. This reduction was 38.3% indoors and 39.1% outdoors for Armigeres, and 36.0% indoors and 32.3% outdoors for Culex species. Intervention impacts on the HBRs were not significant and are attributed to large inter-household and inter cluster variation. Anopheles flavirostris, Anopheles balabacensis and Anopheles maculatus individually impacted the overall malaria infections hazard rate with statistically significance. Though there was SR-based protection against malaria for all Anopheles species (except Anopheles sundaicus), only five (Anopheles aconitus, Anopheles kochi, Anopheles tessellatus, An. maculatus and An. sundaicus) demonstrated statistical significance. The SR numerically reduced Anopheles parity rates indoors and outdoors when compared to the placebo.

Conclusion: Evidence demonstrating that Anopheles vectors bite both indoors and outdoors indicates that currently implemented indoor-based vector control tools may not be sufficient to eliminate malaria. The documented impact of the SR intervention on Aedes, Armigeres and Culex species points to its importance in combatting other vector borne diseases. Studies to determine the impact of spatial repellents on other mosquito-borne diseases is recommended.

Keywords: Anopheles; Anthropophagic; Indonesia; Mosquitoes; Spatial repellent; Sumba.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. Therefore, the authors declare that they have no competing interests.

Figures

Fig. 1
Fig. 1
Map of the study site: sentinel house clusters are marked by circle in Sumba (larger inset), Indonesia (small inset). Spatial repellant (active) clusters 1, 15, 16, 17, 18 and 20 (in red), while placebo clusters 2, 3, 9, 21, 23 and 24 are in blue. Map from Natural Earth. https://www.naturalearthdata.com/
Fig. 2
Fig. 2
Biweekly mean (+ SD) HBR (bpn) of Anopheles mosquitoes by species, treatment and collection location
See this image and copyright information in PMC

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