Targeted application of an organophosphate-based paint applied on windows and doors against Anopheles coluzzii resistant to pyrethroids under real life conditions in Vallée du Kou, Burkina Faso (West Africa)

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Résumé

Background: A novel strategy applying an organophosphate‑based insecticide paint on doors and windows in com‑
bination with long‑lasting insecticide‑treated nets (LLINs) was tested for the control of pyrethroid‑resistant malaria
vectors in a village setting in Vallée du Kou, a rice‑growing area west of Burkina Faso.
Methods: Insecticide Paint Inesfly 5A IGR™, comprised of two organophosphates and an insect growth regulator,
was applied to doors and windows and tested in combination with pyrethroid‑treated LLINs. The killing effect was
monitored for 5 months by early morning collections of anophelines and other culicids. The residual efficacy was
evaluated monthly by WHO bioassays using Anopheles gambiae ‘Kisumu’ and local populations of Anopheles coluzzii
resistant to pyrethroids. The spatial mortality efficacy (SME) at distances of 1 m was also assessed against pyrethroid‑
susceptible and ‑resistant malaria vectors. The frequency of L1014F kdr and Ace‑1R G119S mutations was, respec‑
tively, reported throughout the study. The Insecticide Paint Inesfly 5A IGR had been tested in past studies yielding a
long‑term mortality rate of 80% over 12 months against An. coluzzii, the local pyrethroid‑resistant malaria vector. The
purpose of the present study is to test if treating smaller, targeted surfaces (e.g. doors and windows) was also efficient
in killing malaria vectors.
Results: Treating windows and doors alone yielded a killing efficacy of 100% for 1 month against An. coluzzii resistant
to pyrethroids, but efficacy reduced quickly afterwards. Likewise, WHO cone bioassays yielded mortalities of 80–100%
for 2 months but declined to 90 and 40% 2 and 3 months after treatment, respectively. Mosquitoes exposed to insec‑
ticide paint‑treated surfaces at distances of 1 m, yielded mortality rates of about 90–80% against local pyrethroids‑
resistant An. coluzzii during the first 2 months, but decreased to 30% afterwards. Anopheles coluzzii was reported to be
exclusively the local malaria vector and resistant to pyrethroids with high L1014 kdr frequencyConclusion: The combination of insecticide paint on doors and windows with LLINs yielded high mortality rates in
the short term against wild pyrethroid‑resistant malaria vector populations. A high SME was observed against labora‑
tory strains of pyrethroid‑resistant malaria vectors placed for 30 min at 1 m from the treated/control walls. The applica‑
tion of the insecticide paint on doors and windows led to high but short‑lasting mortality rates. The strategy may be
an option in a context where low cost, rapid responses need to be implemented in areas where malaria vectors are
resistant to pyrethroids.

Mots-clés

Mosquito control, Insecticide resistance, Organophosphates, Insecticide paint, Burkina Faso, Africa, Western