Vector control using insecticides remains one of the most effective means of preventing this disease. However its effectiveness is threatened by the emergence of resistance to insecticides in the main vectors, including Anopheles funestus.
The candidate presents her work
“Assessment of the association between a genomic variation of 4.3 kilobase pairs (kb) and resistance to insecticides in Anopheles funestus, a major malaria vector “ is the research topic covered by Stevia Ntadoun, a master’s student at the University of Yaoundé I, and research student at CRID. Her work aimed at characterising the population of An. funestus from Gounougou (west Region, Cameroon), possessing between two
cytochrome P450 genes, an insertion of a 4.3 kb fragment, while focusing on the determination of its role in resistance to insecticides in this malaria vector.
The results obtained and presented by Stevia Ntadoun revealed that the prevalence of this 4.3kb insertion has increased in the Littoral, Center, Adamaoua, and North regions, and has reached high frequencies (90-100%) in almost all localities, except Gounougou. This rapid selection happened in just about three years. Genotyping mosquitoes recently collected from Gounougou revealed that, this 4.3kb insertion had already spread throughout this population and that this mosquito population is resistant to almost all classes of insecticides except organophosphates and neonicotinoids.
Quantitative PCR (qPCR) results revealed that the three genes surrounding the 4.3kb fragment CYP6P5, CYP6P9b, and CYP6P9a were the most overexpressed. These genes were previously shown to be able to metabolize pyrethroid molecules hence this could explain their sudden selection. Susceptibility tests carried out with cross-bred mosquitoes revealed a strong association between the presence of the insertion and the ability of mosquitoes carrying it to survive exposure to insecticides used in impregnated bed-nets (deltamethrin at 0.05% concentration and permethrin 0.75%). The rapid selection and fixation of the 4.3 kb insertion highlighted in this study reveal the challenges and urgency of developing new molecular and biochemical tools for the early detection of the mechanisms of resistance in the field for appropriate resistance management.
Perspectives
Family photo with CRID
Following the evidence obtained through this study, the author finds it is appropriate that other bio-assays be conducted to investigate the association between the insertion of 4.3 kb and resistance to other pyrethroid insecticides (alpha-cypermethrin) as well as with other classes of insecticides such as carbamates, organochlorines, organophosphates, and neonicotinoids. In addition to what has been done, research on the genetic diversity of the insertion must be done to understand the origin of this mutation; to determine if it is a de NOVO mutation or due to migration. According to Stevia Ntadoun, transcriptional studies should also be conducted to assess the association between the presence of this insertion and the expression of detoxification genes.
Recommendations
The young researcher highlights the need for people to always sleep under impregnated mosquito nets. Public authorities should use control tools based on neonicotinoids, organophosphates, and the synergist PBO in vector control programs. To the scientific community, she recommends regular monitoring and characterization of An. funestus populations in the field in order to detect resistance markers before they are known in the entire population.
