Bendiocarb resistance in Anopheles gambiae s.l. populations from Atacora department in Benin, West Africa: a threat for malaria vector control

Abstract

BackgroundOwing to pyrethroid resistance in An. gambiae, the carbamate and organophosphate insecticides are currently regarded as alternatives or supplements to pyrethroids for use on mosquito net treatments. Resistance monitoring is therefore essential to investigate the susceptibility of An. gambiae s.l to these alternative products.MethodsTwo to three day old adult female Anopheles mosquitoes were reared from larvae collected in the five districts (Kouandé, Natitingou, Matéri, Péhunco, Tanguiéta) of the Atacora department. Mosquitoes were then exposed to WHO impregnated papers. The four treatments consisted of: carbamates (0.1% bendiocarb, 0.1% propoxur) and organophosphates (0.25% pirimiphosmethyl, 1% fenitrothion). PCR assays were run to determine the members of the An. gambiae complex, the molecular forms (M) and (S), as well as phenotypes for insensitive acetylcholinesterase (AChE1) due to ace-1R mutation.ResultsBioassays showed bendiocarb resistance in all populations of An. gambiae s.s. tested. Propoxur resistance was observed in Matéri, Péhunco and Tanguiéta, while it was suspected in Kouandé and Natitingou. As for the organophosphates, susceptibility to pirimiphos-methyl was assessed in all populations. Fenitrothion resistance was detected in Kouandé, Péhunco and Tanguiéta, while it was suspected in Matéri and Natitingou. The S-form was predominant in tested samples (94.44%). M and S molecular forms were sympatric but no M/S hybrids were detected. The ace-1R mutation was found in both S and M molecular forms with frequency from 3.6 to 12%. Although the homozygous resistant genotype was the most prevalent genotype among survivors, the genotypes could not entirely explain the bioassay results.ConclusionEvidence of bendiocarb resistance in An. gambiae populations is a clear indication that calls for the implementation of insecticide resistance management strategies. The ace-1R mutation could not entirely explain the resistance to bendiocarb observed and is highly suggestive of involvement of other resistance mechanisms such as metabolic detoxification.

Evidence of multiple mechanisms providing carbamate and organophosphate resistance in field An. gambiae population from Atacora in Benin

“…The twenty-five females of An. gambiae were introduced into each tube and monitored at different time intervals (10,15,20,30,45, 60 minutes), the number "knocked-down" were recorded. After one hour exposure, mosquitoes were transferred into holding tubes and provided with cotton wool soaked with a 10% honey solution.…”

“…More recently in Benin, several studies pointed out An. gambiae resistance to bendiocarb [20,21] and showed that the mean Ace-1 mutation frequency had increased significantly from 2010 to 2012 after two years of IRS campaign using bendiocarb in Atacora region in the northern part of the country [22,23]. However, these studies cleary showed the evidence of bendiocarb resistance in An.…”

The Anopheles gambiae cE5 salivary protein: a sensitive biomarker to evaluate the efficacy of insecticide-treated nets in malaria vector control

“…Different vector control strategies are currently employed, for example indoor residual spraying (IRS) or insecticide-treated plastic sheeting, but the use of insecticide-treated nets (ITNs) is so far the most efficient and used strategy to reduce malaria transmission and morbidity by decreasing human-vector contact. However, parasite resistance to antimalarial treatment [2] and mosquito vector resistance to insecticides [3,4] seriously impair the success of malaria control measures.…”

Dysfunctional Adaptive Immunity During Parasitic Infections

“…These findings suggest that exposure to parasites and their encoded antigens can induce a degree of clinical immunity and provide the rationale and incentive for pursuing the development of anti-parasitic vaccines. Furthermore, while the advent of novel anti-parasitic drugs have successfully led to a decrease in the incidence rates of parasitic infections, they have also aided in positively selecting for both resistant parasites and their vectors [4, 5]. Thus, alternative immune-based approaches and effective vaccines against Plasmodium and other protozoan and helminth parasites are desperately needed.…”