Distribution and frequency of kdr mutations within Anopheles gambiae s.l. populations and first report of the ace.1 G119S mutation in Anopheles arabiensis from Burkina Faso (West Africa).

Roch K Dabiré,Moussa Namountougou,Chris Bass,Dieudonné D Soma,Patrice Combary,Joseph Bado,Hyacinthe K Toé,Abdoulaye Diabaté,Basil Brooke

doi:10.1371/journal.pone.0101484

Abstract

An entomological survey was carried out at 15 sites dispersed throughout the three eco-climatic regions of Burkina Faso (West Africa) in order to assess the current distribution and frequency of mutations that confer resistance to insecticides in An. gambiae s.l. populations in the country. Both knockdown (kdr) resistance mutation variants (L1014F and L1014S), that confer resistance to pyrethroid insecticides, were identified concomitant with the ace-1 G119S mutation confirming the presence of multiple resistance mechanisms in the An. gambiae complex in Burkina Faso. Compared to the last survey, the frequency of the L1014F kdr mutation appears to have remained largely stable and relatively high in all species. In contrast, the distribution and frequency of the L1014S mutation has increased significantly in An. gambiae s.l. across much of the country. Furthermore we report, for the first time, the identification of the ace.1 G116S mutation in An. arabiensis populations collected at 8 sites. This mutation, which confers resistance to organophosphate and carbamate insecticides, has been reported previously only in the An. gambiae S and M molecular forms. This finding is significant as organophosphates and carbamates are used in indoor residual sprays (IRS) to control malaria vectors as complementary strategies to the use of pyrethroid impregnated bednets. The occurrence of the three target-site resistance mutations in both An. gambiae molecular forms and now An. arabiensis has significant implications for the control of malaria vector populations in Burkina Faso and for resistance management strategies based on the rotation of insecticides with different modes of action.

Highlights

The pyrethroid class of insecticides have become a mainstay for vector control since the ban of DDT due to off-target toxicity and the development of resistance
An extensive monitoring program in Burkina Faso has revealed that the L1014F kdr mutation initially detected in low frequency in the An. gambiae M molecular form and An. arabiensis [11,15] has spread throughout the country and is observed in mosquito populations at relatively high frequency [16,17]
From an applied perspective, the emergence of resistance has significant implications for vector control programmes, especially those focused on the use of ITNs/Long-Lasting Insecticidal Nets (LLINs) or indoor residual sprayings (IRS)

Summary

Introduction

The pyrethroid class of insecticides have become a mainstay for vector control since the ban of DDT due to off-target toxicity and the development of resistance. Initial studies showed that L1014F kdr was most widely distributed in West African An. gambiae s.l. populations [6,8,9] This mutation was observed initially in the S molecular form of An. gambiae s.s. reaching high frequency but was not found either in sympatric mosquitoes of the M molecular form or An. arabiensis populations [5]. More recently this mutation was reported in a small number of individuals of the M and S forms of An. gambiae in Burkina Faso [22] Taken together these results provide fundamental insight into the evolutionary processes underlying resistance in Anopheles gambiae s.l. from an applied perspective, the emergence of resistance has significant implications for vector control programmes, especially those focused on the use of ITNs/Long-Lasting Insecticidal Nets (LLINs) or indoor residual sprayings (IRS). LLINs had shown good control of certain pyrethroid resistant populations [23] reduced efficacy of treated nets against An. gambiae populations with kdr resistance has since been reported [24]

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Results

Conclusion