Abstract
BackgroundMalaria vector control in the Democratic Republic of the Congo is plagued by several major challenges, including inadequate infrastructure, lack of access to health care systems and preventative measures, and more recently the widespread emergence of insecticide resistance among Anopheles mosquitoes. Across 26 provinces, insecticide resistance has been reported from multiple sentinel sites. However, to date, investigation of molecular resistance mechanisms among Anopheles vector populations in DRC has been more limited.MethodsAdult Anopheles gambiae sensu lato (s.l.) and Anopheles funestus s.l. were collected from two sites in Sud-Kivu province and one site in Haut-Uélé province and PCR-screened for the presence of 11 resistance mutations, to provide additional information on frequency of resistance mechanisms in the eastern DRC, and to critically evaluate the utility of these markers for prospective country-wide resistance monitoring.ResultsL1014F-kdr and L1014S-kdr were present in 75.9% and 56.7% of An. gambiae s.l. screened, respectively, with some individuals harbouring both resistant alleles. Across the three study sites, L43F-CYP4J5 allele frequency ranged from 0.42 to 0.52, with evidence for ongoing selection. G119S-ace1 was also identified in all sites but at lower levels. A triple mutant haplotype (comprising the point mutation CYP6P4-I236M, the insertion of a partial Zanzibar-like transposable element and duplication of CYP6AA1) was present at high frequencies. In An. funestus s.l. cis-regulatory polymorphisms in CYP6P9a and CYP6P9b were detected, with allele frequencies ranging from 0.82 to 0.98 and 0.65 to 0.83, respectively.ConclusionsThis study screened the most up-to-date panel of DNA-based resistance markers in An. gambiae s.l. and An. funestus s.l. from the eastern DRC, where resistance data is lacking. Several new candidate markers (CYP4J5, G119S-ace1, the triple mutant, CYP6P9a and CYP6P9b) were identified, which are diagnostic of resistance to major insecticide classes, and warrant future, larger-scale monitoring in the DRC to inform vector control decisions by the National Malaria Control Programme.
Highlights
Malaria vector control in the Democratic Republic of the Congo is plagued by several major challenges, including inadequate infrastructure, lack of access to health care systems and preventative measures, and more recently the widespread emergence of insecticide resistance among Anopheles mosquitoes
Mosquito species identification and P. falciparum screening A subset of eight individual An. gambiae s.l. each from Tchonka, Tushunguti and Kibali and An. funestus s.l. from Tchonka and Tushunguti were identified to specieslevel by PCR; all were determined to be An. gambiae s.s. (24/24) and An. funestus s.s. (16/16), respectively
Anopheles gambiae s.l. target site mutation screening Mosquito individuals morphologically identified as An. gambiae s.l. were screened for the presence of eight mutations (Tables 2 and 3)
Summary
Malaria vector control in the Democratic Republic of the Congo is plagued by several major challenges, including inadequate infrastructure, lack of access to health care systems and preventative measures, and more recently the widespread emergence of insecticide resistance among Anopheles mosquitoes. Malaria vector control in the DRC relies on universal coverage of insecticide-treated nets (ITNs), via mass campaigns, community-based top-ups to maintain high coverage, and continuous distributions through routine antenatal care (ANC) and child immunization services by the national expanded programme on immunization (EPI) [5]. Recent estimates of net access and use across the country remain low, with the proportion of households with at least one ITN for every two people declining from 47% to 2013/14 to 44% in 2017/18, and the proportion of children under five years old reported sleeping under an ITN the previous night decreasing from 56% to 2013/14 to 51% in 2017/18 [7]
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