Abstract
Malaria is endemic in sub-Saharan Africa with considerable burden for human health. Major insecticide resistance mechanisms such as kdr R and ace-1 R alleles constitute a hindrance to malaria vector control programs. Anopheles gambiae bearing both kdr and ace-1 resistant alleles are increasingly recorded in wild populations. In order to maintain the efficacy of vector control strategies, the characterization of concomitant kdr and ace-1 resistance, and their pleiotropic effects on malaria vector phenotype on insecticide efficacy are important. Larval and adult bioassays were performed with different insecticide classes used in public health following WHO standard guidelines on four laboratory Anopheles gambiae strains, sharing the same genetic background but harboring distinct resistance status: KISUMU with no resistance allele; ACERKIS with ace-1 R allele; KISKDR with kdr R allele and ACERKDRKIS with both resistance alleles’ ace-1 R and kdr R . Larval bioassays indicate that the homozygote resistant strain harboring both alleles (ACERKDRKIS) displayed slightly but significantly higher resistance level to various insecticides like carbamates (bendiocarb, p < 0.001; propoxur, p = 0.02) and organophosphates (chlorpyriphos-methyl, p = 0.002; fenitrothion, p < 0.001) when compared to ACERKIS strain. However, no differences were recorded between ACERKDRKIS and KISKDR resistance level against permethrin (Pyrethroid, p = 0.7) and DDT (Organochlorine, p = 0.24). For adult bioassays, the percentages of mosquitoes knocked down were significantly lower for ACERKDRKIS than for KISKDR with permethrin (p = 0.003) but not with deltamethrin. The percentage of mortality from adult bioassays was similar between ACERKDRKIS and ACERKIS with carbamates and organophosphates, or between ACERKDRKIS and KISKDR with pyrethroid and DDT. Concerning acetylcholinesterase enzyme, ACERKDRKIS strain showed similarAChE1 activity than that of ACERKIS. The presence of both kdr R and ace-1 R alleles seems to increase the resistance levels to both carbamate and organophosphate insecticides and at operational level, may represent an important threat to malaria vector control programs in West Africa.
Highlights
Malaria is endemic in sub-Saharan Africa with considerable burden for human health
Mosquito strains Four strains of An. gambiae s.s. were used in this study (Table 1): i) The KISUMU reference strain, susceptible to all insecticides used in this study [62]. ii) The ACERKIS strain, which is homozygous for the G119S mutation and resistant to both OPs and CXs insecticides [51]. iii)
We did not record a significant difference between ACERKDRKIS and KISKDR resistance levels against permethrin (p = 0.7) and DDT (p = 0.24)
Summary
Malaria is endemic in sub-Saharan Africa with considerable burden for human health. Major insecticide resistance mechanisms such as kdrR and ace-1Ralleles constitute a hindrance to malaria vector control programs. Anopheles gambiae bearing both kdr and ace-1 resistant alleles are increasingly recorded in wild populations. In order to maintain the efficacy of vector control strategies, the characterization of concomitant kdr and ace-1 resistance, and their pleiotropic effects on malaria vector phenotype on insecticide efficacy are important. Human malaria parasites are exclusively transmitted by Anopheles mosquitoes (Diptera: Culicidae). In most of African countries, the control of mosquito vectors is the only affordable measure for the fight against malaria [9,10]
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