Laboratory and experimental hut trial evaluation of VECTRON ™ T500 for indoor residual spraying (IRS) against insecticide resistant malaria vectors in Burkina Faso

Koama Bayili; Hyacinthe D Ki; Bazoma Bayili; Bazoumana Sow; Abdoulaye Ouattara; Graham Small; Aristide S Hien; Roch K Dabire; Abdoulaye Diabate

doi:10.12688/gatesopenres.13578.2

Laboratory and experimental hut trial evaluation of VECTRON ^™ T500 for indoor residual spraying (IRS) against insecticide resistant malaria vectors in Burkina Faso

Gates Open Res. 2022 Jul 25:6:57. doi: 10.12688/gatesopenres.13578.2. eCollection 2022.

Authors

Koama Bayili¹, Hyacinthe D Ki¹, Bazoma Bayili^{1

2}, Bazoumana Sow^{1

2}, Abdoulaye Ouattara¹, Graham Small³, Aristide S Hien⁴, Roch K Dabire¹, Abdoulaye Diabate^{1

2}

Affiliations

¹ Entomologist, Institut de Recherche en Sciences de la Santé, Bobo-dioulasso, 545, Burkina Faso.
² Entomologist, Université Nazi Boni, Bobo-Dioulasso, Burkina Faso.
³ Senior Technical Manager, Innovative Vector Control Consortium, Liverpool, Liverpool L3 5QA, UK.
⁴ Institut de Recherche en Sciences de la Santé, Bobo-Dioulasso, Burkina Faso.

Abstract

Background: Malaria cases in some areas could be attributed to vector resistant to the insecticide. World Health Organization recommended insecticides for vector control are limited in number. It is essential to find rotational partners for existing Indoor Residual Spraying (IRS) products. VECTRON ^™ T500 is a novel insecticide with broflanilide as active ingredient. It has a mode of action on mosquitoes completely different to usually used. The aim of this study was to determine the optimum effective dose and efficacy of VECTRON ^TM T500 against susceptible and resistant strains of Anopheles in Burkina Faso. Methods: VECTRON™T500 was sprayed at 50, 100 and 200 mg/m² doses onto mud and concrete blocks using Potter Spray Tower. The residual activity of broflanilide was assessed through cone bioassays 1 week and then monthly up to 14 months post spraying. Its efficacy was evaluated at 100 and 150 mg/m² against wild free-flying mosquitoes in experimental huts on both substrates. Actellic 300CS was applied at 1000 mg/m² as reference product. Cone assays were conducted monthly, using susceptible and resistant mosquito strains. Results: In the laboratory, VECTRON ^™ T500 showed residual efficacy (≥80% mortality) on An. gambiae Kisumu up to 12 and 14 months, respectively, on concrete and mud blocks. Similar results were found with 100 and 200 mg/m² using An. coluzzii pyrethroid resistant strain. In experimental huts, a total of 19,552 An. gambiae s.l. were collected. Deterrence, blood-feeding inhibition and exophily with VECTRON™ treated huts were very low. At 100 and 150 mg/m², mortality of wild An. gambiae s.l. ranged between 55% and 73%. Monthly cone bioassay mortality remained >80% up to 9 months. Conclusions: VECTRON™ T500 shows great potential as IRS formulation for malaria vector control. It can be added to the arsenal of IRS products for use in rotations to control malaria and manage mosquito insecticide resistance.

Keywords: Anopheles gambiae; Insecticide Residual Spray (IRS); Malaria; Pyrethroid resistance; Residual efficacy; VECTRON™ T500.

Grants and funding

This work was supported by the Bill & Melinda Gates Foundation [OPP1148615] through the Innovative Vector Control Consortium (IVCC). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.