Abstract
BackgroundInsecticide resistance is a growing concern for malaria control and vector control effectiveness relies on assessing it distribution and understanding its evolution.MethodsWe assessed resistance levels and the frequencies of two major target-site mutations, L1014F-VGSC and G119S-ace-1, conferring resistance to pyrethroids (PYRs) and carbamates/organophosphates (CXs/OPs) insecticides. These data were compared to those acquired between 2006 and 2010 to follow resistance evolutionary trends over ten years.ResultsWe report the results of a 3-year survey (2013–2015) of insecticide resistance in 13 localities across the whole country of Benin. Permethrin (PYR) resistance was found in all populations tested, L1014F-VGSC being almost fixed everywhere, while bendiocarb resistance was limited to a few localities, G119S-ace-1 remaining rare, with very limited variations during surveyed period. Interestingly, we found no effect of the type of insecticide pressure on the dynamics of these mutations.ConclusionsThese results confirm both the high prevalence of PYR resistance and the potential of CXs/OPs as short- to medium-term alternatives in Benin. They also underline the need for regular resistance monitoring and informed management in their usage, as the G119S-ace-1 mutation is already present in Benin and surrounding countries. Their unwise usage would rapidly lead to its spread, which would jeopardize PYR-resistant Anopheles control.
Highlights
Insecticide resistance is a growing concern for malaria control and vector control effectiveness relies on assessing it distribution and understanding its evolution
These localities were selected according to insecticide use for crops protection or for malaria vector control and priority was given to localities involved in previous studies, to assess resistance dynamics (Table 1): (i) seven localities (Cotonou, Grand-Popo, Bohicon, Abomey, Glazoué, Bembèrèkè and Kandi), where vegetables and cotton are produced, with strong economic interests for the farmers and government, are mainly exposed to agricultural treatments; (ii) four localities (Tori-Bossito, Avrankou, Djougou and Natitingou) are less exposed to these agricultural insecticides, but have been selected for specific experimental malaria vector control intervention (MVCI), with more intense vector control interventions, i.e. more frequent turnover of bednets and IRS implementation; and (iii) two localities have little insecticide exposure, with limited insecticides usage for domestic production or public-health (Covè and Comè)
We found a significant effect of the interaction between the nature of the main insecticide pressures and the collection year on mortality (GLMM, likelihood ratio tests (LRT) corrected for overdispersion, P < 0.001; note that a large overdispersion, 3.01, was observed)
Summary
Insecticide resistance is a growing concern for malaria control and vector control effectiveness relies on assessing it distribution and understanding its evolution. Controlling mosquito vectors of human diseases is a major health issue, in sub-Saharan Africa where Anopheles gambiae (s.l.) is the main vector of malaria transmission. Pyrethroid insecticides (PYRs) have been the cornerstone of malaria prevention in Africa for almost two decades, after Abuja Declaration in 2000, when Benin and the rest West African countries set-up a proper plan against malaria control [2]. The ability of vectors to survive insecticide treatments (i.e. become resistant) is a growing concern, as it may threaten vector control effectiveness for preventing malaria transmission [3,4,5,6]. Insecticide resistance is widespread in natural populations in West Africa and more in Benin, Burkina Faso and Ivory Coast [7,8,9].
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