Assessing the efficacy of two dual-active ingredients long-lasting insecticidal nets for the control of malaria transmitted by pyrethroid-resistant vectors in Benin: study protocol for a three-arm, single-blinded, parallel, cluster-randomized controlled trial

Manfred Accrombessi, Jackie Cook, Corine Ngufor, Arthur Sovi, Edouard Dangbenon, Boulais Yovogan, Hilaire Akpovi, Aurore Hounto, Charles Thickstun, Gil G Padonou, Filemon Tokponnon, Louisa A Messenger, Immo Kleinschmidt, Mark Rowland, Martin C Akogbeto, Natacha Protopopoff, Manfred Accrombessi, Jackie Cook, Corine Ngufor, Arthur Sovi, Edouard Dangbenon, Boulais Yovogan, Hilaire Akpovi, Aurore Hounto, Charles Thickstun, Gil G Padonou, Filemon Tokponnon, Louisa A Messenger, Immo Kleinschmidt, Mark Rowland, Martin C Akogbeto, Natacha Protopopoff

Abstract

Background: Long-lasting insecticidal nets (LLINs) are currently the primary method of malaria control in sub-Saharan Africa and have contributed to a significant reduction in malaria burden over the past 15 years. However, this progress is threatened by the wide-scale selection of insecticide-resistant malaria vectors. It is, therefore, important to accelerate the generation of evidence for new classes of LLINs.

Methods: This protocol presents a three-arm superiority, single-blinded, cluster randomized controlled trial to evaluate the impact of 2 novel dual-active ingredient LLINs on epidemiological and entomological outcomes in Benin, a malaria-endemic area with highly pyrethroid-resistant vector populations. The study arms consist of (i) Royal Guard® LLIN, a net combining a pyrethroid (alpha-cypermethrin) plus an insect growth regulator (pyriproxyfen), which in the adult female is known to disrupt reproduction and egg fertility; (ii) Interceptor G2® LLIN, a net incorporating two adulticides (alpha-cypermethrin and chlorfenapyr) with different modes of action; and (iii) the control arm, Interceptor® LLIN, a pyrethroid (alpha-cypermethrin) only LLIN. In all arms, one net for every 2 people will be distributed to each household. Sixty clusters were identified and randomised 1:1:1 to each study arm. The primary outcome is malaria case incidence measured over 24 months through active case detection in a cohort of 25 children aged 6 months to 10 years, randomly selected from each cluster. Secondary outcomes include 1) malaria infection prevalence (all ages) and prevalence of moderate to severe anaemia in children under 5 years old, measured at 6 and 18 months post-intervention; 2) entomological indices measured every 3 months using human landing catches over 24 months. Insecticide resistance intensity will also be monitored over the study period.

Discussion: This study is the second cluster randomised controlled trial to evaluate the efficacy of these next-generation LLINs to control malaria transmitted by insecticide-resistant mosquitoes. The results of this study will form part of the WHO evidence-based review to support potential public health recommendations of these nets and shape malaria control strategies of sub-Saharan Africa for the next decade.

Trial registration: ClinicalTrials.gov, NCT03931473 , registered on 30 April 2019.

Keywords: Benin; Chlorfenapyr, pyriproxyfen, Royal Guard®; Cluster randomized controlled trial; Dual-active ingredient long-lasting insecticidal nets; Entomological inoculation rate; Interceptor® G2; Malaria case incidence; Malaria prevalence.

Conflict of interest statement

The authors declare that they have no competing interests.

Figures

Fig. 1
Fig. 1
Study area. Map showing Cove, Zagnanado and Ouinhi Districts, located in Zou department, central Benin, West Africa (Panel a); the 60 study clusters identified with core and buffer area and intervention allocation (Panel b); a minimum of 1000 m area was created between households in adjacent clusters (Panel c). Source of map: Own from the study investigators (CT, JC, MA, ED).
Fig. 2
Fig. 2
Summary of study design

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