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Author: search.filters.author.Covenant University DissertationSubject: search.filters.subject.Anopheles gambiae

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    EXPRESSION PROFILES OF CYTOCHROME P450 GENES ASSOCIATED WITH PERMETHRIN RESISTANCE IN Anopheles gambiae s.l. IN ADO-ODO OTA, OGUN STATE
    (Covenant University Ota, 2025-10) AINA, Motunrayo Oluwabunmi; Covenant University Dissertation
    Malaria remains a significant tropical public health threat, where resistance to insecticides constitutes a severe hindrance to the efficacy of its primary vector control methods. Routinely applied pyrethroid insecticides are increasingly facing resistance associated with the overexpression of cytochrome P450 genes in the Anopheles gambiae sensu lato, underscoring the urgent search into these associated genes. This study assessed the expression profile of cytochrome P450 genes associated with permethrin resistance in Anopheles gambiae sensu lato collected from three localities in Ado-Odo, Ota. Ethical approval was obtained from the Covenant Health Research Ethics Committee (CHREC). Based on the WHO standard, female adult An. gambiae larvae (n=300) were collected using the dipping method and reared into adults in the Insectary Laboratory. These laboratory-reared mosquitoes were phenotypically identified using microscopy and genotypically characterised using polymerase chain reaction (PCR) based on species-specific primers. Thereafter, a WHO susceptibility bioassay was conducted in vivo for mosquitocidal activity against these adult mosquitoes in four replicates at a 0.75% permethrin concentration each on day 3 post-adult emergence. The relative expression of the cytochrome P450 genes (CYP6M2 and CYP6P3) was carried out using the quantitative real-time PCR (qRT-PCR). Higher occurrence rate of An. gambiae sensu lato. was recorded in Nestle (80%)), Chelsea (78%)) compared Gasline (30%) localities of Ado-Odo. In vivo insecticide susceptibility testing revealed consistently low mortality rates across all the replicates, ranging from 20% to 32% indicating increased resistance to permethrin. Results of relative expression of cytochrome P450 genes showed higher fold changes in CYP6M2 ranging from 0.63 to 122.4 than in CYP6P3 0.63 to 34.39 across the tested mosquito replicates. Thus, this study has further emphasized the prevalence of An. gambiae sensu lato members in Ado-Odo, Ota. Additionally, the results of higher permethrin resistant and upregulation of CYP6M2 and CYP6P3 genes inform the imminent need for integrated resistance surveillance with newer vector management for improved malaria control.
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    DETECTION OF kdr AND rdl MUTATIONS IN PERMETHRIN-EXPOSED Anopheles gambiae
    (Covenant University Ota, 2025-09) AKANNI, Mosunmola Hannah; Covenant University Dissertation
    The emergence of insecticide resistance in malaria vectors compromises the effectiveness of vector control interventions, including long-lasting insecticidal nets and indoor residual spraying. This study assessed insecticide resistance, species composition, and the mechanism of resistance in Anopheles gambiae mosquitoes. Larvae and pupae were gotten from Nestle, Ota, Ogun state, Nigeria and were reared to adulthood at the Covenant University Insectary, 3-5 days non-blood fed female mosquitoes were exposed to 0.75% permethrin according WHO tube assay protocol, polymerase chain reaction was used to detect Anopheles gambiae species and allele specific polymerase chain reaction was used to detect kdr and rdl mutation. WHO susceptibility assays revealed resistance to permethrin. Molecular identification confirmed that An. gambiae was the predominant species, indicating a high risk of malaria transmission. Genotyping of the kdr west (L1014F) and rdl loci showed high frequencies of resistant alleles, with the heterozygous RS genotype being the most common in both loci. Hardy–Weinberg analyses revealed a non-random distribution of genotypes, reflecting selection pressure from insecticide exposure. Co-occurrence analysis suggested that kdr and rdl mutations largely occur independently, indicating that multi-resistance is emerging but not yet widespread. This study provides insight into the genetic basis and prevalence of insecticide resistance in malaria vectors, suggesting the need for continuous surveillance and evidence-based vector control approaches to preserve the efficacy of malaria interventions in Nigeria.
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    IMPACT OF SELECTED ESSENTIAL OILS AND PIPERONYL BUTOXIDE ON PYRETHROID RESISTANCE IN Anopheles gambiae IN OTA
    (Covenant University Ota, 2025-09) JEGEDE, Precious Osekafore; Covenant University Dissertation
    Malaria remains a major public health challenge in Nigeria, with rising pyrethroid resistance in Anopheles gambiae undermining vector control strategies. Resistance is largely driven by detoxification enzymes and target-site mutations. Although piperonyl butoxide (PBO) is widely used as an insecticide synergist, its environmental and health risks highlight the need for safer alternatives. This study evaluated the potential of basil and geranium essential oils to inhibit detoxification enzymes, enhance permethrin efficacy, and compared their effects to PBO in An. gambiae. Adult females were collected, morphologically identified, and allocated into treatment groups for WHO susceptibility bioassays, enzyme activity assays, and allele-specific PCR (AS-PCR) for kdr mutation detection. Mosquitoes were exposed to permethrin alone (0.75%), basil or geranium essential oils at 1 (10 μL/mL), 5 (50 μL/mL), and 10% (100 μL/mL) v/v, or sub-lethal synergist assays combining permethrin (0.75%) with basil (1%), geranium (1%), or PBO (4%). Permethrin alone produced 25% mortality, confirming resistance according to WHO criteria. As separate insecticides, basil oil induced 0, 90, and 100% mortality at 10, 50, and 100 μL/mL, respectively, while geranium oil induced 10, 100, and 100% mortality at the same concentrations. In synergist assays, basil + permethrin achieved 25% mortality, geranium + permethrin 55%, and PBO + permethrin 60%. Enzyme assays showed no significant variation in GST activity, whereas cytochrome P450 activity was significantly elevated in permethrin-only treatments (p < 0.05) but remained near-control levels with basil, geranium, and PBO. AS-PCR detected a high frequency of the kdr-west L1014F allele (R = 0.76), with most mosquitoes homozygous resistant (RR). These findings confirm strong pyrethroid resistance in An. gambiae from Ota and highlight geranium oil and basil oil, as promising environmentally friendly insecticides and synergists for malaria vector control.
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    COMPARATIVE EXPRESSION PROFILING OF SELECTED GLUTATHIONE S-TRANSFERASE GENES IN BLOOD-FED AND DELTAMETHRIN-EXPOSED Anopheles gambiae
    (Covenant University Ota, 2025-09) FOLAMADE, Joshua Kayode; Covenant University Dissertation
    Malaria remains a leading public health challenge in sub-Saharan Africa, with Nigeria contributing the highest global burden. Anopheles gambiae is the major vector of this disease in Nigeria. Vector control strategies rely heavily on pyrethroid-based tools such as long-lasting insecticidal nets and indoor residual spraying. Metabolic resistance mediated by glutathione S-transferases (GSTs), particularly GSTe2, GSTe3, and GSTMS3, has been implicated in pyrethroid detoxification. Meanwhile, blood feeding induces profound physiological and molecular changes in mosquitoes, including alterations in detoxification pathways, suggesting a potential interaction with insecticide resistance. This study investigated how blood feeding and deltamethrin exposure influence the expression of GSTe2, GSTe3, and GSTMS3 in An. gambiae from Ota, Ogun State, Nigeria. Mosquitoes were reared from field-collected larvae and assigned to four experimental groups: blood-fed + deltamethrin exposed, blood-fed only, sugar-fed + deltamethrin exposed, and sugar-fed only (control). Susceptibility to deltamethrin was assessed using WHO bioassays and gene expression was quantified by qPCR. Results showed that blood-fed mosquitoes were significantly more susceptible to deltamethrin than sugar-fed counterparts, with higher mortality and faster knockdown times. At the molecular level, GSTe2 expression was generally down-regulated following deltamethrin exposure, while GSTe3 and GSTMS3 exhibited variable responses depending on feeding status. It was observed that blood feeding was the most consistent factor influencing GST expression, with insecticide exposure exerting context-dependent effects. These findings highlight that blood feeding modulates detoxification gene expression and susceptibility outcomes in An. gambiae, which implies dynamic physiological influences on resistance phenotypes. By integrating ecological behavior with molecular resistance mechanisms, this study underscores the importance of accounting for feeding status in resistance monitoring and vector control strategies. Locally relevant data such as these are critical for guiding malaria control interventions in Nigeria’s high-burden regions.