Entomological longitudinal surveys in two contrasted eco-climatic settings in Cameroon reveal a high malaria transmission from Anopheles funestus associated with GSTe2 metabolic resistance

Natchema S. Fonkou, Brice; Tchouakui, Magellan; Menze, Benjamin D.; Mugenzi, Leon M. J.; Fofie, Derrick; Nguiffo-Nguete, Daniel; Nkengazong, Lucia; Tombi, Jeannette; Wondji, Charles S.

doi:10.1186/s12879-023-08698-8

Cited by 3 publications

(1 citation statement)

References 59 publications

(81 reference statements)

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“…The first round of amplification in a 20 µL reaction volume comprised 10 µM of genus-specific primers rPLU-5 and rPLU-6, 4 µL of 2 × MyTaq Mix (Bioline, Meridian Bioscience, Germany), 0.2 U MyTaq polymerase, 10.58 µL of PCR water and ~ 20 ng of gDNA. The second round of amplification entailed same constituents except template being 4 µL of the first PCR product and species-specific primer pairs each in separate PCRs (rFAL1 + rFAL2, rVIV1 + rVIV2, rMAL1 + rMAL2, and rOVAL1 + rOVAL2) 23 . In both first and second round amplification, the cycling conditions were 5 min at 95 °C; 25 cycles (first round, 30 cycles for second round) of 30 s at 94 °C, 2 min at 58 °C and 2 min at 72 °C and final extension for 5 min at 72 °C.…”

Section: Mosquito Screening For Malaria Parasite Infectionmentioning

confidence: 99%

Vectorial drivers of malaria transmission in Jabi Tehnan district, Amhara Regional State, Ethiopia

Belay,

Asale,

Sole

et al. 2024

Sci Rep

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Among the factors affecting the effectiveness of malaria control is poor knowledge of the entomologic drivers of the disease. We investigated anopheline populations as part of a baseline study to implement house screening of windows and doors as a supplementary malaria control tool towards elimination in Jabi Tehnan district, Amhara Regional State of Ethiopia. The samples were surveyed monthly using CDC light traps between June 2020 and May 2021. Mosquito trap density (< 3 mosquitoes/trap) was low, however, with a high overall Plasmodium sporozoite rate (9%; indoor = 4.3%, outdoor = 13.1%) comprising P. falciparum (88.9%) and P. vivax (11.1%). Anopheles gambiae s.l., mostly An. arabiensis, comprised > 80% of total anopheline captures and contributed ~ 42% of Plasmodium-infected mosquitoes. On the other hand, morphologically scored Anopheles funestus s.l., constituting about 6% of anopheline collections, accounted for 50% of sporozoite-infected mosquitoes. Most of the infected An. funestus s.l. specimens (86.7%) were grouped with previously unknown or undescribed Anopheles species previously implicated as a cryptic malaria vector in the western Kenyan highlands, confirming its wider geographic distribution in eastern Africa. Other species with Plasmodium infection included An. longipalpis C, An. theileri, An. demillioni, and An. nili. Cumulatively, 77.8% of the infected mosquitoes occurred outdoors. These results suggest efficient malaria parasite transmission despite the low vector densities, which has implications for effective endpoint indicators to monitor malaria control progress. Additionally, the largely outdoor infection and discovery of previously unknown and cryptic vectors suggest an increased risk of residual malaria transmission and, thus, a constraint on effective malaria prevention and control.

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Section: Mosquito Screening For Malaria Parasite Infectionmentioning

confidence: 99%

Vectorial drivers of malaria transmission in Jabi Tehnan district, Amhara Regional State, Ethiopia

Belay,

Asale,

Sole

et al. 2024

Sci Rep

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Two highly selected mutations in the tandemly duplicatedCYP6P4aandCYP6P4bdrive pyrethroid resistance inAnopheles funestus

Tatchou-Nebangwa,

Mugenzi,

Muhammad

et al. 2024

Preprint

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Gaining a comprehensive understanding of the genetic mechanisms underlying insecticide resistance in malaria vectors is crucial for optimising the effectiveness of insecticide-based vector control methods and developing diagnostic tools for resistance management. Considering the heterogeneity of metabolic resistance in major malaria vectors, the implementation of tailored resistance management strategies is essential for successful vector control. In this study, we provide evidence demonstrating that two highly selected mutations in the tandemly duplicated cytochrome P450 genes namely CYP6P4a and CYP6P4b, are driving pyrethroid insecticide resistance in the major malaria vector Anopheles funestus, in West Africa. Through a continent-wide polymorphism survey, we observed heightened indications of directional selection in both genes between 2014 and 2021. By conducting in vitro insecticide metabolism assays with recombinant enzymes expressed from both genes, we established that mutant alleles under selection exhibit higher metabolic efficiency compared to their wild-type counterparts. Furthermore, using the GAL4-UAS transgenic system, we demonstrated that transgenic Drosophila melanogaster flies overexpressing mutant alleles displayed an increased resistance to pyrethroids. These findings were in agreement with in silico characterisation, which highlighted changes in enzyme active site architecture that enhance the affinity of mutant alleles for type I and II pyrethroids. Furthermore, we developed two DNA-based assays capable of detecting the CYP6P4a-M220I and CYP6P4b-D284E mutations, showing their current confinement to West Africa. Genotype/phenotype correlation analyses revealed that these markers are strongly associated with resistance to types I and II pyrethroids and combine to drastically reduce the efficacy of pyrethroid bednets. Overall, our study makes available two field-applicable insecticide resistance molecular markers that will help in the monitoring and better management of insecticide resistance in West Africa.

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Indoor residual spraying of experimental huts in Cameroon highlights the potential of Fludora® Fusion to control wild pyrethroid-resistant malaria vectors

Thiomela,

Tchouakui,

Menze

et al. 2024

BMC Infect Dis

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Elevated resistance to pyrethroids in major malaria vectors has led to the introduction of novel insecticides including neonicotinoids. There is a fear that efficacy of these new insecticides could be impacted by cross-resistance mechanisms from metabolic resistance to pyrethroids. In this study, after evaluating the resistance to deltamethrin, clothianidin and mixture of clothianidin + deltamethrin in the lab using CDC bottle assays, the efficacy of the new IRS formulation Fludora® Fusion was tested in comparison to clothianidin and deltamethrin applied alone using experimental hut trials against wild free-flying pyrethroid-resistant Anopheles funestus from Elende and field An. gambiae collected from Nkolondom reared in the lab and released in the huts. Additionally, cone tests on the treated walls were performed each month for a period of twelve months to evaluate the residual efficacy of the sprayed products. Furthermore, the L1014F-kdr target-site mutation and the L119F-GSTe2 mediated metabolic resistance to pyrethroids were genotyped on a subset of mosquitoes from the EHT to assess the potential cross-resistance. All Anopheles species tested were fully susceptible to clothianidin and clothianidin + deltamethrin mixture in CDC bottle assay while resistance was noted to deltamethrin. Accordingly, Fludora® Fusion (62.83% vs 42.42%) and clothianidin (64.42% vs 42.42%) induced significantly higher mortality rates in EHT than deltamethrin (42.42%) against free flying An. funestus from Elende in month 1 (M1) and no significant difference in mortality was observed between the first (M1) and sixth (M6) months of the evaluation (P > 0.05). However, lower mortality rates were recorded against An. gambiae s.s from Nkolondom (mortality rates 50%, 45.56% and 26.68%). In-situ cone test on the wall showed a high residual efficacy of Fludora® Fusion and clothianidin on the susceptible strain KISUMU (> 12 months) and moderately on the highly pyrethroid-resistant An. gambiae strain from Nkolondom (6 months). Interestingly, no association was observed between the L119F-GSTe2 mutation and the ability of mosquitoes to survive exposure to Fludora® Fusion, whereas a trend was observed with the L1014F-kdr mutation. This study highlights that Fludora® Fusion, through its clothianidin component, has good potential of controlling pyrethroid-resistant mosquitoes with prolonged residual efficacy. This could be therefore an appropriate tool for vector control in several malaria endemic regions.

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Entomological longitudinal surveys in two contrasted eco-climatic settings in Cameroon reveal a high malaria transmission from Anopheles funestus associated with GSTe2 metabolic resistance

Cited by 3 publications

References 59 publications

Vectorial drivers of malaria transmission in Jabi Tehnan district, Amhara Regional State, Ethiopia

Vectorial drivers of malaria transmission in Jabi Tehnan district, Amhara Regional State, Ethiopia

Two highly selected mutations in the tandemly duplicatedCYP6P4aandCYP6P4bdrive pyrethroid resistance inAnopheles funestus

Indoor residual spraying of experimental huts in Cameroon highlights the potential of Fludora® Fusion to control wild pyrethroid-resistant malaria vectors

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