Evidence of Insecticide Resistance to Pyrethroids and Bendiocarb in from Tsararano, Marovoay District, Madagascar.

INTRODUCTION

In Madagascar, malaria control relies on the countrywide use of long lasting insecticide treated bed nets (LLINs) and on indoor residual spraying (IRS) in the central highland area as well as a small area on the eastern coast. We tested insecticide resistance mechanisms of from Tsararano, a malaria endemic village in the coastal health district of Marovoay.

METHODS

Insecticide susceptibility bioassays were done in July 2017 on first-generation (F1) to assess (i) the susceptibility to permethrin (0.05%), deltamethrin (0.05%), DDT (4%), malathion (5%), fenitrothion (1%), and bendiocarb (0.1%); (ii) the effect of preexposure to the piperonyl butoxide (PBO) synergist; and (iii) the enzymatic activities of cytochrome P450, esterases, and glutathione S-transferases (GST).

RESULTS

Our results demonstrated that . was phenotypically resistant to pyrethroids and bendiocarb, with a mortality rate (MR) of 33.6% (95%CI: 24.5-43.7%) and 86% (95%CI: 77.6-92.1%), respectively. In contrast, . were 100% susceptible to DDT and organophosphates (malathion and fenitrothion). Preexposure of . to PBO synergist significantly restored the susceptibility to bendiocarb (MR=100%) and increased the MR in the pyrethroid group, from 96% (95%CI: 90.0-98.9%) to 100% for deltamethrin and permethrin, respectively ( = 43, = 3, ). Enzymatic activities of cytochrome P450 and -esterases were significantly elevated among . compared with the IPM strain (Mann-Whitney = 30; = , respectively). No significant differences of -esterases activities compared to the IPM reference strain were observed (Mann-Whitney ).

CONCLUSION

In Tsararano, despite the absence of an IRS programme, there is evidence of high levels of insecticide resistance to pyrethroids and bendiocarb in .