Insecticide resistance profiles in malaria vector populations from Sud-Kivu in the Democratic Republic of the Congo

Abstract

Background Insecticide resistance has become a widespread problem causing a decline in the effectiveness of vector control tools in sub-Saharan Africa. In this situation, ongoing monitoring of vector susceptibility to insecticides is encouraged by the WHO to guide national malaria control programmes. Our study was conducted from April to November 2018 in Tchonka (Sud-Kivu, Democratic Republic of the Congo) and reported primary data on the resistance status of Anopheles funestus and Anopheles gambiae. Methods Insecticide susceptibility bioassays were performed on wild populations of A. funestus and A. gambiae using WHO insecticide-impregnated papers at discriminating concentration. In addition, PCR was performed to identify mosquito species and to detect kdr and ace-1R mutations involved in insecticide resistance. Results Bioassay results show resistance to all tested insecticides except pirimiphos-methyl, propoxur, fenitrothion and malathion with a mortality rate ranging from 95.48 to 99.86%. The addition of piperonyl butoxide (PBO) increased the susceptibility of vectors to deltamethrin and alpha-cypermethrin by exhibiting a mortality ranging from 91.50 to 95.86%. The kdr mutation was detected at high frequencies (approximately 0.98) within A. gambiae while ace-1R was not detected. Conclusions This study provides useful data on the insecticide resistance profiles of malaria vector populations to better manage vector control. Our results highlight that, despite the high level of resistance, organophosphorus compounds and pyrethroids + PBO remain effective against the vectors.

Investigating molecular mechanisms of insecticide resistance in the Eastern Democratic Republic of the Congo

“…The L1014S- kdr allele frequency of 0.78 in this dataset from 2017-2019 supports these previous surveys, with evidence for ongoing selection of this allele. One additional study has been performed in Tchonka from April–November, 2018 [ 11 ] indicating almost complete fixation of L1014F- kdr (0.98), which was also consistent with this study’s observations of slightly lower frequencies of this mutation (0.75), which may have risen over time under selection. The predictive association between L1014F- kdr and L1014S- kdr and resistance phenotype (i.e.…”

“…The predictive association between L1014F- kdr and L1014S- kdr and resistance phenotype (i.e. survival or death following an insecticide bioassay or exposure to a vector control intervention) is not absolute [ 30 ], but both mutations have been proposed to play a larger contributing role in resistance to type I (permethrin) versus type II (alpha-cypermethrin and deltamethrin) pyrethroids [ 31 ], which broadly aligns with observations of lower permethrin susceptibility, compared to deltamethrin or alpha-cypermethrin, in some local vector populations [ 10 , 11 , 14 , 32 ]; it is also important to note that differences in discriminating concentrations of pyrethroids used for resistance monitoring and other coinciding resistance mechanisms may also explain some of these discrepancies [ 33 ]. This study also demonstrated a proportion of An.…”

“…gambiae s.l. across the country and can be found in high frequencies in some locales [ 11 , 14 ]. Prior to this study, molecular resistance monitoring had been undertaken in Kibali in 2011–2012, reporting a moderate prevalence of L1014S- kdr (0.61) and lower levels of L1014F- kdr (0.1) and L1014F/S- kdr (0.26) [ 12 ] (Additional file 1 : Table S1).…”

“…funestus s.l. has been reported from multiple sentinel sites [ 8 ], including reduced susceptibility to DDT, deltamethrin and permethrin in Kwilu [ 9 ], Nord-Ubangi [ 10 ] and Sud-Kivu provinces [ 11 ], and to deltamethrin and DDT in Haut-Uélé province [ 12 ]. In Kinshasa, high intensity pyrethroid and organochlorine resistance has been observed, with An.…”

Investigating Molecular Mechanisms of Insecticide Resistance in the Eastern Democratic Republic of the Congo

“…funestus s.l. has been reported from multiple sentinel sites [8], including reduced susceptibility to DDT, deltamethrin and permethrin in Kwilu province [9], Nord-Ubangi [10] and Sud-Kivu provinces [11], and to deltamethrin and DDT in Haut-Uélé province [12]. In Kinshasa, high intensity pyrethroid and organochlorine resistance has been observed, with An.…”