Issue |
Parasite
Volume 32, 2025
|
|
---|---|---|
Article Number | 40 | |
Number of page(s) | 8 | |
DOI | https://doi.org/10.1051/parasite/2025036 | |
Published online | 01 July 2025 |
Research Article
Bioassay tests reveal for the first time pyrethroid resistance in Aedes mosquitoes from Franceville, southeast Gabon, Central Africa
Des tests biologiques révèlent pour la première fois une résistance aux pyréthrinoïdes chez les moustiques Aedes de Franceville, sud-est du Gabon, en Afrique centrale
1 Département de Biologie de l’Université des Sciences et Techniques de Masuku (USTM), BP 901, Franceville, Gabon
2
Unité de Recherche en Ecologie de la Santé du Centre Interdisciplinaire de Recherches Médicales de Franceville (CIRMF), BP 769, Franceville, Gabon
3
Department of Zoology and Entomology, Faculty of Natural and Agricultural Sciences, University of the Free State, Phuthaditjhaba 9866, Republic of South Africa
4
Laboratoire d’Écologie Vectorielle et Parasitaire, Université Cheikh Anta Diop de Dakar, BP 5005 Dakar, Sénégal
5
Research Institute in Tropical Ecology (IRET), BP 13354, Libreville, Gabon
6
Centre for Research in Infectious Diseases (CRID), PO Box 13591, Yaoundé, Cameroun
7
MIVEGEC, Univ. Montpellier, CNRS, IRD, 34394 Montpellier, France
* Corresponding authors: judicael.obame@live.fr; obamenkoghej@ufs.ac.za; christophe.paupy@ird.fr
Received:
18
September
2024
Accepted:
9
June
2025
The spread of resistance to insecticides, such as pyrethroids, in Aedes vectors increases the risk of spread of arboviral diseases. In Gabon, the insecticide resistance profiles of Ae. aegypti and Ae. albopictus species remain poorly known. During a study to monitor the dynamics of Aedes populations in Franceville, in south-east Gabon, the resistance profiles of these two species to pyrethroids, organophosphates and carbamates were assessed. Susceptibility tests on adults and synergist tests with piperonyl butoxide (PBO) were carried out as per the World Health Organization protocol. The results showed that Ae. aegypti and Ae. albopictus were susceptible to permethrin, pirimiphos-methyl and bendiocarb. However, both species were resistant to deltamethrin (mortality: 67% for Ae. aegypti; 33% for Ae. albopictus). Exposure to a 5-fold dose of deltamethrin increased mortality to 100% and 91% for Ae. aegypti and Ae. albopictus, respectively. Resistance to alpha-cypermethrin was also recorded (mortality: 82% for Ae. aegypti; 64.6% for Ae. albopictus). Pre-exposure to PBO resulted in the restoration of susceptibility to deltamethrin and alpha-cypermethrin for Ae. aegypti, and a significant increase in mortality for Ae. albopictus. These data provide the first evidence of pyrethroid resistance in Aedes in Gabon and could help to establish more effective control measures against arbovirus vectors.
Résumé
La propagation de la résistance aux insecticides, tels que les pyréthrinoïdes, chez les vecteurs Aedes augmente le risque de propagation des arboviroses. Au Gabon, les profils de résistance aux insecticides des espèces Ae. aegypti et Ae. albopictus restent mal connus. Lors d’une étude de suivi de la dynamique des populations d’Aedes à Franceville, dans le sud-est du Gabon, les profils de résistance de ces deux espèces aux pyréthrinoïdes, aux organophosphorés et aux carbamates ont été évalués. Des tests de sensibilité sur adultes et des tests synergétiques au butoxyde de pipéronyle (PBO) ont été réalisés conformément au protocole de l’Organisation Mondiale de la Santé. Les résultats ont montré qu’Ae. aegypti et Ae. albopictus étaient sensibles à la perméthrine, au pirimiphos-méthyl et au bendiocarbe. Cependant, les deux espèces étaient résistantes à la deltaméthrine (mortalité : 67 % pour Ae. aegypti, 33 % pour Ae. albopictus). L’exposition à une dose de deltaméthrine multipliée par 5 a augmenté la mortalité, respectivement à 100 % pour Ae. aegypti et 91 % et pour Ae. albopictus. Une résistance à l’alpha-cyperméthrine a également été observée (mortalité : 82 % pour Ae. aegypti, 64,6 % pour Ae. albopictus). Une préexposition au PBO a entraîné la restauration de la sensibilité à la deltaméthrine et à l’alpha-cyperméthrine pour Ae. aegypti, et une augmentation significative de la mortalité pour Ae. albopictus. Ces données fournissent la première preuve de résistance aux pyréthroïdes chez les Aedes au Gabon et pourraient aider à établir des mesures de contrôle plus efficaces contre les vecteurs d’arbovirus.
Key words: Aedes / Insecticide resistance / Pyrethroids / Organophosphates / Carbamates / PBO
Edited by: Jérôme Depaquit
© J. Obame-Nkoghe et al., published by EDP Sciences, 2025
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Introduction
Arboviruses (arthropod-borne viruses) are vector-borne pathogens transmitted by blood-sucking arthropods such as mosquitoes, ticks, and sandflies [39]. The diseases they can cause include dengue fever, chikungunya, Zika, and yellow fever, which pose a global health threat. These diseases, confined to tropical and sub-tropical regions for a long time, are now affecting temperate areas [8, 11, 34]. The spread of arboviruses is closely linked to the geographical expansion of their vectors, particularly Aedes mosquitoes, among which Aedes aegypti (Linnaeus, 1762) and Aedes albopictus (Skuse, 1894) are the main vector species.
Aedes aegypti is a species native to Africa, and known to be the main vector of dengue fever throughout the world [16]. Aedes albopictus, originating from Asia, has succeeded in colonizing other continents during the past four decades [30] through the development of human activities such as the international trade of used tires [30, 40]. In Central Africa, the invasion by Ae. albopictus has been found to be associated with numerous outbreaks or silent epidemic waves of chikungunya, dengue, and Zika [1, 31, 33].
Given the absence of any specific curative treatment or effective vaccine that can be used in the general population (except for the yellow fever virus), vector control is the key strategy for reducing the risks posed by the vector-borne transmission of these arboviruses. The World Health Organization (WHO) recommends the use of insecticides during outbreaks [44]. However, the emergence of resistance to the most commonly used insecticides is a real obstacle to the progress made to date [25], and on a global scale, mosquito resistance to insecticides represents a major challenge for vector control programmes. Various studies across Africa [7], Asia [41, 47], and Latin America [38] have shown worrying trends in insecticide resistance, requiring global as well as context-adapted approaches to develop sustainable management strategies.
In Gabon, due to the heavy burden of endemic malaria in the region, the use of insecticides mainly targets Anopheles mosquitoes to reduce the transmission of this disease. Several studies have been carried out across the country to characterize the resistance profile of Anopheles mosquitoes to the main families of insecticides (pyrethroids, carbamates, and organophosphates) [4, 5, 27, 32]. Conversely, among Aedes, despite the endemic circulation of dengue fever and chikungunya epidemics recorded in the country in 2007 and 2010 [15, 29, 31], very little insecticide resistance monitoring and control data on Ae. albopictus and Ae. aegypti populations are currently available [19].
To improve our knowledge of insecticide resistance in Ae. albopictus and Ae. aegypti in Gabon, we conducted an exploratory study alongside a broader survey on mosquito population dynamics in southeastern Gabon. This study aimed to address the existing gap by assessing the resistance profiles of these two vector species to pyrethroids and other insecticide classes, including organophosphates and carbamates in Franceville, southeastern Gabon.
Materials and methods
Ethics
All mosquito collections were conducted in accordance with national regulations and with permission from local authorities under the number N°AR33/23/MESRSIT/CENAREST/CG/CST/CSAR.
Study area
This study was conducted in Franceville (S01°37′15″, E13°34′58″), located in the Haut-Ogooué province in southeastern Gabon (Fig. 1). Situated over 600 km from Libreville, the capital city, Franceville is the third most populous city in Gabon, following Libreville and Port-Gentil. Franceville is characterized by an equatorial climate featuring two rainy seasons (a longer one from March to June and a shorter one from October to November) and two intervening dry seasons. Franceville is divided into four districts, each marked by a semi-urban environment. Over the past two decades, the city has experienced outbreaks of dengue and chikungunya, ranking it among the most affected areas in the country, and hosts a high density of Aedes mosquitoes. However, until today, no vector control programmes have been considered, especially given the need to document the status of resistance to insecticides to inform potential future control measures.
![]() |
Figure 1 Localisation of Franceville. |
Mosquito sampling
The sampling occurred between March and June 2023, during the rainy season. We used G0 adult stages that emerged from field-collected eggs or larvae to perform the bioassays. Collections of eggs and larvae were conducted using randomly placed ovitraps in domestic and peri-domestic sites across the four districts of Franceville (2–3 per site). Opportunistic inspections of domestic or discarded water containers were conducted in the same zones to gather Aedes immature stages (larvae and pupae). To obtain a general overview of resistance patterns in Franceville, we used composite populations from the four districts for each species. In each district, we deployed 10–15 plastic ovitraps [spaced 20 m apart to reduce potential competition effects] to collect eggs, while larvae and pupae were sampled from various water containers [30–35 per district], including flower pots, cinder blocks, and discarded tires. Each ovitrap consisted of a black plastic cup filled with up to 300 mL of tap water and a 15 cm × 5 cm wooden strip, which served as an oviposition substrate. The wooden strips were removed every 5 to 7 days and taken to the insectary for drying and subsequent egg hatching. The dried eggs (representing the G1 generation) were then placed in plastic trays containing 1 L of distilled water, where they were hatched and reared to the adult stage. Larvae collected from each site (also representing the G0 generation) were preserved in 500 mL plastic containers and transported to the insectary. There, they were transferred into 30 cm × 15 cm plastic rearing trays until the adult stage. In cases where field-collected water volume was insufficient, we supplemented with up to 1 L of distilled water. Larvae were fed daily with 1–2 g of Tetramin baby® fish food. All trays were maintained under room conditions: temperature 27 °C ± 2 °C, relative humidity 80% ± 10%, and a 12:12 h (light:dark) photoperiod. Upon emergence, adults were individually introduced into a dry hemolysis tube plugged with a cotton ball, and morphologically identified using a binocular microscope and “customized” taxonomic keys based on the updates of Edwards’ identification keys for Ethiopian mosquitoes [13] and Huang’s key for the subgenus Stegomyia of Aedes mosquitoes from the Afrotropical region [17]. After identification, adults Ae. albopictus and Ae. aegypti coming from each district were pooled by species in cages and fed exclusively on 10% sucrose. In order to ensure synchronised age of mosquitoes, new cages were used to pool emerging adults every 5 days. They were maintained at insectary conditions, as indicated earlier, until tests.
Susceptibility and synergist tests
Bioassays were performed on adult female mosquitoes obtained from eggs and larvae to assess the phenotypic resistance of Ae. albopictus and Ae. aegypti to insecticide molecules according to the World Health Organization (WHO) tube test protocol [44]. A strain of Ae. albopictus from the remote forested village of Kessipougou (S00°54′27.7″, E012°47′36.5″), presumed pesticide-naïve, was used as the susceptible reference strain in these tests. In Kessipougou, most residents report not using insecticides, and eggs were collected along forest interfaces at about 30 m of the nearest house using 10 ovitraps (5 at each side of the village) activated simultaneously for 5 days and positioned at least 30 m from each other. Before testing Franceville mosquitoes, we conducted preliminary assays to validate insecticide efficacy. No prior published resistance data were available for the Kessipougou strain, but our results confirmed the assumption of the strain’s full susceptibility, establishing its suitability as a control reference. The impregnated papers used in the bioassays were sourced from the Vector Control Research Unit (VCRU) at the University of Sains, Malaysia. The VCRU is the WHO collaborating center for the manufacturing of insecticide-impregnated papers. Five insecticide compounds from three major classes (pyrethroids, organophosphates, and carbamates) were used in the tests. The discriminating concentrations (DCs) used in this study for testing Aedes mosquitoes were those available from the VCRU and recommended by the WHO before the latest adopted DCs. Specifically, the pyrethroids included 0.75% permethrin (later revised to 0.4%), 0.05% deltamethrin (later revised to 0.03%), and 0.05% alpha-cypermethrin (later revised to 0.08% for Ae. albopictus, but maintained at 0.05% for Ae. aegypti). The organophosphates comprised 0.25% pirimiphos-methyl (later revised to 60 mg/m2, equivalent to 0.15%), while the carbamates included 0.1% bendiocarb (later revised to 0.2%). These DCs were those available at the time of the study. Insecticide-free papers were used for control tests with silicone oil as solvent for the tests with pyrethroids, or olive oil for the tests with organophosphates and carbamates. For each insecticide DC, four test replicates (insecticide-impregnated papers) and two controls (insecticide-free papers) were used. For each replicate, 25 G1 non-blood-fed females aged between 2 and 5 days were introduced into exposure tubes containing insecticide-impregnated filter papers for 1 h and knockdown (Kd) was recorded for each pyrethroid. Post-exposed mosquitoes were transferred into holding tubes and kept at the insectary conditions with free access to 10% sucrose, and mortality was recorded 24 h post-exposure. Only when resistance to a given insecticide was confirmed four replicates at 5-fold of the initial dose were performed to assess the intensity of the observed resistance. However, this was not possible for alpha-cypermethrin given that 5-fold doses (0.25%) were not available for testing.
To assess the potential role of metabolic resistance mechanisms, synergistic tests with 4% piperonyl butoxide (PBO) were performed on G1 adult females aged between 2 and 5 days. PBO works by inhibiting certain metabolic detoxifying enzymes such as cytochrome P450 monooxygenases (P450s), which are involved in the metabolic neutralization of insecticide compounds, especially pyrethroids [3]. To process the tests, females were pre-exposed for 1 hour to papers impregnated with PBO, then immediately exposed to the selected insecticides (or insecticide-free papers for controls), following the procedure described above for standard tests.
Data analysis
Interpretation of mortality rates was based on the WHO criteria. Mosquitoes were considered resistant when mortality was less than 90%, and susceptible when mortality was greater than or equal to 98%. However, when mortality was greater than or equal to 90% and less than 98%, resistance to the insecticide tested was suspected. Corrections were applied when necessary, taking into account the mortality in controls using Abbott’s formula [44]. R software, version 4.3.3, was used to produce the graphical representations and to perform appropriate statistical tests. The chi-squared test was used to compare the mortality percentage between Ae. albopictus and Ae. aegypti for each insecticide. When chi-squared test conditions were not met, Fisher’s exact test was used as a non-parametric alternative. All differences were considered statistically significant when the p-value was below 0.05.
Results
Phenotypic insecticide resistance profile
A total of 1,600 female mosquitoes (800 Ae. albopictus and 800 Ae. aegypti) were exposed to insecticides. Results showed that all Ae. albopictus and Ae. aegypti females were knocked down after 60 min of exposure to all pyrethroid insecticides. Aedes albopictus from the remote forested village of Kessipougou had 100% mortality for all insecticides tested. Exposure of mosquitoes to bendiocarb (carbamate) and pirimiphos-methyl (organophosphate) resulted in 100% mortality rates for both Ae. albopictus and Ae. aegypti. In contrast, exposure to pyrethroids resulted in variable mortality rates. Aedes albopictus was susceptible to permethrin (98% mortality), but resistant to deltamethrin (33%) and alpha-cypermethrin (64.6%). Aedes aegypti was susceptible to permethrin, but resistant to deltamethrin (71%) and alpha-cypermethrin (82%) (Fig. 2). Results on intensity testing demonstrated that deltamethrin resistance was low in Ae. aegypti, but moderate in Ae. albopictus populations, with mortality rates of 100% and 91% at 5X standard dose, respectively.
![]() |
Figure 2 Mortality of adult females 24 h after 1-hour exposure to insecticides and pre-exposure to PBO. The red dotted line indicates 90% mortality, and the green one 98% mortality. |
Statistical analysis showed that the mortality rates recorded after exposure to alpha-cypermethrin 0.05%, deltamethrin 0.05%, and deltamethrin 0.25% were significantly higher in Ae. aegypti compared to Ae. albopictus (Table 1).
Comparison of mortality rates in Ae. aegypti vs. Ae. albopictus.
Assessment of potential resistance mechanisms
The results of bioassays with the synergist PBO in Ae. albopictus showed a partial recovery of susceptibility to 0.05% deltamethrin (from 33% mortality without pre-exposure to PBO to 84% mortality after 60 min pre-exposure to PBO, χ2 = 50.6, df = 1, p < 0.001), and to 0.05% alpha-cypermethrin (from 64.6% mortality without pre-exposure to PBO to 91% mortality after 60 min pre-exposure to PBO, χ2 = 18.2, df = 1, p < 0.001). In Ae. aegypti, pre-exposure to PBO resulted in a complete recovery of susceptibility to 0.05% deltamethrin (from 67% mortality without pre-exposure to PBO to 100% mortality after pre-exposure to PBO, Fisher p < 0.001), and to 0.05% alpha-cypermethrin (from 82% mortality without pre-exposure to PBO to 100% mortality after pre-exposure to PBO, Fisher p < 0.001) (Fig. 2). This partial or complete recovery of susceptibility suggests the probable involvement of active metabolic detoxification enzymes, particularly cytochrome P450 monooxygenases, in pyrethroid resistance in both species.
Discussion
To date, limited research has been conducted in monitoring insecticide resistance in Aedes mosquitoes, particularly Ae. albopictus and Ae. aegypti, across Africa. According to recent studies spanning the past two decades and encompassing 18 African countries [14, 18, 24, 26, 28, 36, 43, 46], widespread confirmed or suspected resistance to DDT (dichlorodiphenyltrichloroethane) has been documented in both species. In contrast, resistance to pyrethroids remains less evident and appears to be an emerging concern, with a higher prevalence reported in Ae. aegypti (recorded in 16 out of the 18 countries) compared to Ae. albopictus (detected in only 3 countries). A similar pattern was observed for carbamate or organophosphate insecticides (9/18 for Ae. aegypti versus 2/18 for Ae. albopictus) [14, 43]. In Gabon specifically, resistance assessments in Aedes mosquitoes have been restricted to temephos for larval stages, and to DDT, deltamethrin, propoxur, and fenitrothion for adults, with confirmed resistance in adult Ae. aegypti to DDT [19].
The present study aimed to characterise the phenotypic profile of insecticide resistance of the species Ae. albopictus and Ae. aegypti in southeastern Gabon. The observed mortality rates from exposure tests with pirimiphos-methyl (organophosphate) and bendiocarb (carbamate) indicate that both species are susceptible to these insecticides. These findings are consistent with those reported in southern Benin (West Africa), where populations of Ae. aegypti were shown to be susceptible to both insecticides [21]. Similar susceptibility to bendiocarb has also been documented in Cameroon (Central Africa) for populations of both Ae. albopictus and Ae. aegypti [12, 20, 26]. In both studies (Benin and Cameroon), pirimiphos-methyl and bendiocarb were used at concentrations similar to those used in our investigation in Gabon. There could be similar operational strategies in these African countries, where the use of carbamates and organophosphates is more controlled and maintains effectiveness. However, these results contrast with findings from Asia, particularly in Singapore, where populations of Ae. albopictus have been reported as resistant to pirimiphos-methyl, with mortality rates ranging from 45% to 75% [23]. Indeed, Lee et al. suggested the long-term implementation of dengue control using pirimiphos-methyl for vector control in Singapore as a promoting factor of the resistance of Ae. albopictus populations. Therefore, operational differences in both African and Asian contexts may explain the contrasting results. In the context of vector control strategies, maintaining low or reduced selection pressure on insecticide-resistant mosquito populations through controlled, reduced, or minimal use of a specific insecticide may help preserve or restore their susceptibility [6]. Therefore, the results that we observed could be attributed, in part, to the fact that pirimiphos-methyl and bendiocarb are not employed in public health initiatives in Gabon. Additionally, their limited use in agriculture, as suggested by a similar study on Anopheles mosquitoes in Mouila, southern Gabon [22], may also explain these findings.
Exposure to pyrethroids showed that both Ae. albopictus and Ae. aegypti were susceptible to 0.75% permethrin, but resistant to 0.05% deltamethrin and 0.05% alpha-cypermethrin. These findings represent the first documented evidence of resistance to alpha-cypermethrin and susceptibility to permethrin in these species. However, the results for deltamethrin contrast with earlier data from Libreville, north-western Gabon, where Ae. aegypti was reported as susceptible to a slightly higher concentration (0.06%) nearly 15 years ago [19]. Collectively, these results provide the first confirmed evidence of pyrethroid resistance in Aedes mosquitoes in Gabon. The earlier susceptibility could have resulted from a lower selection pressure than the present study period, such as the less vulgarised use of pesticides in urban market gardening, known as a key driver in resistance [2]. Pyrethroid resistance in Aedes mosquitoes has been documented across multiple African regions [14, 43]. For example, Ae. albopictus and Ae. aegypti in Cameroon were found to be resistant to permethrin [46], as well as to deltamethrin and alpha-cypermethrin [26, 45]. While the prevalence of pyrethroid resistance is increasing, the underlying mechanisms remain incompletely understood. One potential driver is the extensive and often unregulated application of pyrethroids for malaria vector control, which exerts substantial selection pressure on mosquito populations [2], including non-target species. Additionally, the widespread use of pyrethroid-based pesticides in agricultural practices may further accelerate the development of resistance in Aedes populations [45]. In Franceville, malaria vector control is poorly implemented. However, urban vegetable farming is common, and the use of pesticides by farmers is poorly regulated, making it a potential indirect source of resistance selection pressure.
We showed that mortality rates for deltamethrin and alpha-cypermethrin were significantly higher in the native species Ae. aegypti compared to the invasive Ae. albopictus. One possible explanation may be that Ae. albopictus possesses greater innate resistance potential (genetic traits) or adaptive capacity (genetic and/or environmental factors) to these insecticides compared to Ae. aegypti. This further highlights the need to monitor in particular the spatiotemporal dynamics of insecticide resistance for this newly introduced species in the country, where it is an active vector of arboviruses [31], to better anticipate appropriate control strategies.
Pre-exposure to PBO fully restored susceptibility to deltamethrin and alpha-cypermethrin in Ae. aegypti, and significantly increased mortality in Ae. albopictus. This could suggest that the cytochrome P450 monooxygenase enzymes play the main role in the observed phenotypic resistance [10, 26].
We observed that all the mosquitoes tested were susceptible to the knockdown (Kd) effect. It is known that mutations such as F1534C, V1016G, V1016I, S989P, or L1014F in the voltage-gated sodium channel (vgsc) gene are associated with Kd resistance in Aedes mosquitoes [9, 38]. Thus, in the absence of molecular investigations, our phenotypic results may suggest the absence of these target-site resistance mutations in Ae. aegypti and Ae. albopictus, although this cannot be confirmed without genotypic analysis. Our observations are nonetheless broadly consistent with findings observed in Ae. aegypti populations from Senegal [37]. Therefore, from a public health strategy perspective, one of the solutions likely to restore insecticide susceptibility in these vectors in case they are resistant could be a more strategic and appropriate regulation of insecticide/pesticide use, integrating synergists in formulations to bypass the metabolic mechanisms that might be involved in resistance. Moreover, the efficacy of bendiocarb and pirimiphos-methyl observed in Ae. albopictus and Ae. aegypti makes these insecticides reliable alternatives to pyrethroids in Gabon. However, given their associated toxic effects on non-target organisms [42], they will require controlled use in case of emergencies.
Conclusion
This exploratory study provides the first evidence of pyrethroid resistance in Ae. albopictus and Ae. aegypti populations in Franceville and, more broadly, in Gabon. These unprecedented findings reveal, for the first time, traits of resistance to pyrethroid insecticides in Aedes mosquito populations within the country. From a public health perspective, this study underscores the urgent need to intensify research on insecticide susceptibility in Aedes vectors throughout Gabon, including at a national level, to better inform control strategies. Addressing critical gaps, particularly in the characterisation of genetic mutations in the vgsc gene associated with pyrethroid resistance, as well as the metabolic mechanisms linked to resistant strains, is essential for the development of effective intervention strategies. In addition, integrated surveillance and control combining emerging genetic tools such as the sterile insect technique, biological control, environmental management, social mobilisation, and cross-sectoral collaboration [35] are promising alternatives.
Acknowledgments
We thank the Centre National de Recherche Scientifique et Technologique (CENAREST, Gabon), the Interdisciplinary Centre for Medical Research of Franceville (CIRMF) and the Masuku University of Science and Technology (USTM) for the support provided. Special thanks to Dr Illich Manfred Mombo from CIRMF for the useful tips on IT tools and Dr Dieudonné Nkoghe for insightful advice during manuscript writing. We thank the GRAVIR IRD – International Research Network for their collaboration in this research.
Funding
This study received financial support from the European Union (Grant no. ARISE-PP-FA-072 to JON), through the African Research Initiative for Scientific Excellence (ARISE), pilot programme. ARISE is implemented by the African Academy of Sciences with support from the European Commission and the African Union Commission. This study also benefited from internal financial support from the University of the Free State, South Africa (to PVO). The contents of this document are the sole responsibility of the authors and can under no circumstances be regarded as reflecting the position of the European Union, the African Academy of Sciences, the African Union Commission, or the institutions to which the authors are affiliated. The funders played no role in design of the study, collection and analysis of data, decision to publish or preparation of the manuscript.
Conflicts of interest
The authors declare that they have no conflict of interest.
Author contribution statement
Conceptualisation: JO-N, FMK; Data curation: FMK, JO-N, BN, YON; Formal analysis: JO-N, FMK, EHAD; Acquisition of funding: JO-N, PVO; Bibliographic research: FMK; Methodology: JO-N, FMK, BN, YON; Project administration: JO-N; Resources: JO-N, PVO, EHAD, EHAN, PK; Software: JO-N, FMK, AO, BN; Supervision: JO-N; Validation: JO-N, BK, CP, PK, EHAN; Visualisation: JO-N; Original draft: FMK; Writing-reviewing and editing: JO-N, FMK, BN, YON, AO, NMLP, BM, FM, BK, OT, EHAN, EHD, CP, PK, PVO.
References
- Abe H, Ushijima Y, Loembe MM, Bikangui R, Nguema-Ondo G, Mpingabo PI, Zadeh VR, Pemba CM, Kurosaki Y, Igasaki Y. 2020. Re-emergence of dengue virus serotype 3 infections in Gabon in 2016–2017, and evidence for the risk of repeated dengue virus infections. International Journal of Infectious Diseases, 91, 129–136. [Google Scholar]
- Akogbéto MC, Djouaka RF, Kindé-Gazard DA. 2006. Screening of pesticide residues in soil and water samples from agricultural settings. Malaria Journal, 5, 22. [Google Scholar]
- Bernard CB, Philogene BJ. 1993. Insecticide synergists: role, importance, and perspectives. Journal of Toxicology and Environmental Health, 38, 199–223. [Google Scholar]
- Boussougou-Sambe ST, Ngossanga B, Doumba-Ndalembouly AG, Boussougou LN, Woldearegai TG, Mougeni F, Mba TN, Edoa JR, Dejon-Agobé JC, Awono-Ambene P, Kremsner PG, Kenguele HM, Borrmann S, Mordmüller B, Adegnika AA. 2023. Anopheles gambiae s.s. resistance to pyrethroids and DDT in semi-urban and rural areas of the Moyen-Ogooué Province, Gabon. Malaria Journal, 22, 382. [Google Scholar]
- Boussougou-Sambe ST, Woldearegai TG, Doumba-Ndalembouly AG, Ngossanga B, Mba RB, Edoa JR, Zinsou JF, Honkpehedji YJ, Ngoa UA, Dejon-Agobé JC, Borrmann S, Kremsner PG, Mordmüller B, Adegnika AA. 2022. Assessment of malaria transmission intensity and insecticide resistance mechanisms in three rural areas of the Moyen Ogooué Province of Gabon. Parasites & Vectors, 15, 217. [Google Scholar]
- Bouyer J, de Gentile L, Chandre F. 2017. Chapitre 5. La lutte antivectorielle, in Entomologie médicale et vétérinaire, Duvallet G, Fontenille D, Robert V, Editors, OpenEdition, IRD Éditions, p. 89–120. [Google Scholar]
- Busari LO, Raheem HO, Iwalewa ZO, Fasasi KA, Adeleke MA. 2023. Investigating insecticide susceptibility status of adult mosquitoes against some class of insecticides in Osogbo metropolis, Osun State, Nigeria. PLoS One, 18, e0285605. [Google Scholar]
- Caputo B, Russo G, Manica M, Vairo F, Poletti P, Guzzetta G, Merler S, Scagnolari C, Solimini A. 2020. A comparative analysis of the 2007 and 2017 Italian chikungunya outbreaks and implication for public health response. PLoS Neglected Tropical Diseases, 14, e0008159. [Google Scholar]
- Chen M, Du Y, Nomura Y, Zhorov BS, Dong K. 2020. Chronology of sodium channel mutations associated with pyrethroid resistance in Aedes aegypti. Archives of Insect Biochemistry and Physiology, 104, e21686. [CrossRef] [PubMed] [Google Scholar]
- Das P, Das S, Saha A, Raha D, Saha D. 2024. Effects of deltamethrin exposure on the cytochrome P450 monooxygenases of Aedes albopictus (Skuse) larvae from a dengue-endemic region of northern part of West Bengal, India. Medical and Veterinary Entomology, 38, 269–279. [Google Scholar]
- Delisle E, Rousseau C, Broche B, Leparc-Goffart I, L’Ambert G, Cochet A, Prat C, Foulongne V, Ferré JB, Catelinois O, Flusin O, Tchernonog E, Moussion IE, Wiegandt A, Septfons A, Mendy A, Moyano MB, Laporte L, Maurel J, Jourdain F, Reynes J, Paty MC, Golliot F. 2015. Chikungunya outbreak in Montpellier, France, September to October 2014. Eurosurveillance, 20, 21108. [Google Scholar]
- Djiappi-Tchamen B, Nana-Ndjangwo MS, Tchuinkam T, Makoudjou I, Nchoutpouen E, Kopya E, Talipouo A, Bamou R, Mayi MPA, Awono-Ambene P. 2021. Aedes mosquito distribution along a transect from rural to urban settings in Yaoundé, Cameroon. Insects, 12, 819. [Google Scholar]
- Edwards FW. 1941. Mosquitoes of the Ethiopian Region. III.-Culicine Adults and Pupae. London/Dorking UK: Adlard and Sons Limited. [Google Scholar]
- Egid BR, Coulibaly M, Dadzie SK, Kamgang B, McCall PJ, Sedda L, Toe KH, Wilson AL. 2022. Review of the ecology and behaviour of Aedes aegypti and Aedes albopictus in Western Africa and implications for vector control. Current Research in Parasitology & Vector-Borne Diseases, 2, 100074. [CrossRef] [PubMed] [Google Scholar]
- Gabor JJ, Schwarz NG, Esen M, Kremsner PG, Grobusch MP. 2016. Dengue and chikungunya seroprevalence in Gabonese infants prior to major outbreaks in 2007 and 2010: a sero-epidemiological study. Travel Medicine and Infectious Disease, 14, 26–31. [Google Scholar]
- Gubler DJ. 1998. Dengue and dengue hemorrhagic fever. Clinical Microbiology Reviews, 11, 480–496. [CrossRef] [PubMed] [Google Scholar]
- Huang Y-M. 2004. The subgenus Stegomyia of Aedes in the Afrotropical Region with keys to the species (Diptera: Culicidae). Zootaxa, 700, 1–120. [Google Scholar]
- Kamgang B, Acântara J, Tedjou A, Keumeni C, Yougang A, Ancia A, Bigirimana F, Clarke SE, Gil VS, Wondji C. 2024. Entomological surveys and insecticide susceptibility profile of Aedes aegypti during the dengue outbreak in Sao Tome and Principe in 2022. PLoS Neglected Tropical Diseases, 18, e0011903. [Google Scholar]
- Kamgang B, Marcombe S, Chandre F, Nchoutpouen E, Nwane P, Etang J, Corbel V, Paupy C. 2011. Insecticide susceptibility of Aedes aegypti and Aedes albopictus in Central Africa. Parasites & Vectors, 4, 79. [Google Scholar]
- Kampango A, Hocke EF, Hansson H, Furu P, Haji KA, David J-P, Konradsen F, Saleh F, Weldon CW, Schiøler KL, Alifrangis M. 2022. High DDT resistance without apparent association to kdr and Glutathione-S-transferase (GST) gene mutations in Aedes aegypti population at hotel compounds in Zanzibar. PLoS Neglected Tropical Diseases, 16, e0010355. [Google Scholar]
- Konkon AK, Padonou GG, Osse R, Salako AS, Zoungbédji DM, Sina H, Sovi A, Tokponnon F, Aïkpon R, Noukpo H. 2023. Insecticide resistance status of Aedes aegypti and Aedes albopictus mosquitoes in southern Benin, West Africa. Tropical Medicine and Health, 51, 22. [Google Scholar]
- Koumba A, Koumba CR, Mintsa Nguema R, Ondo P, Bibang G, Comlan P. 2018. Susceptibilité d’Anopheles gambiae s.s. et An. coluzzii aux organophosphorés et aux carbamates en zones d’exploitation industrielle de palmiers à huile à Mouila, Gabon. Bulletin de la Société de Pathologie Exotique, 111, 176–182. [CrossRef] [PubMed] [Google Scholar]
- Lee R, Choong C, Goh B, Ng L, Lam-Phua S. 2014. Bioassay and biochemical studies of the status of pirimiphos-methyl and cypermethrin resistance in Aedes (Stegomyia) aegypti and Aedes (Stegomyia) albopictus (Diptera: Culicidae) in Singapore. Tropical Biomedicine, 31, 670–679. [Google Scholar]
- Maiga A-A, Sombié A, Zanré N, Yaméogo F, Iro S, Testa J, Sanon A, Koita O, Kanuka H, McCall PJ, Weetman D, Badolo A. 2024. First report of V1016I, F1534C and V410L kdr mutations associated with pyrethroid resistance in Aedes aegypti populations from Niamey, Niger. PLoS One, 19, e0304550. [Google Scholar]
- Mnzava AP, Knox TB, Temu EA, Trett A, Fornadel C, Hemingway J, Renshaw M. 2015. Implementation of the global plan for insecticide resistance management in malaria vectors: progress, challenges and the way forward. Malaria Journal, 14, 173. [Google Scholar]
- Montgomery M, Harwood JF, Yougang AP, Wilson-Bahun TA, Tedjou AN, Keumeni CR, Kilpatrick AM, Wondji CS, Kamgang B. 2022. Spatial distribution of insecticide resistant populations of Aedes aegypti and Ae. albopictus and first detection of V410L mutation in Ae. aegypti from Cameroon. Infectious Diseases of Poverty, 11, 90. [Google Scholar]
- Mourou J-R, Coffinet T, Jarjaval F, Pradines B, Amalvict R, Rogier C, Kombila M, Pagès F. 2010. Malaria transmission and insecticide resistance of Anopheles gambiae in Libreville and Port-Gentil, Gabon. Malaria Journal, 9, 321. [Google Scholar]
- Ould Lemrabott MA, Briolant S, Gomez N, Basco L, Ould Mohamed Salem Boukhary A. 2023. First report of kdr mutations in the voltage-gated sodium channel gene in the arbovirus vector, Aedes aegypti, from Nouakchott, Mauritania. Parasites & Vectors, 16, 464. [Google Scholar]
- Pagès F, Peyrefitte CN, Mve MT, Jarjaval F, Brisse S, Iteman I, Gravier P, Nkoghe D, Grandadam M. 2009. Aedes albopictus mosquito: the main vector of the 2007 chikungunya outbreak in Gabon. PLoS One, 4, e4691. [Google Scholar]
- Paupy C, Delatte H, Bagny L, Corbel V, Fontenille D. 2009. Aedes albopictus, an arbovirus vector: from the darkness to the light. Microbes and Infection, 11, 1177–1185. [Google Scholar]
- Paupy C, Kassa Kassa F, Caron M, Nkoghé D, Leroy EM. 2012. A chikungunya outbreak associated with the vector Aedes albopictus in remote villages of Gabon. Vector Borne and Zoonotic Diseases (Larchmont, NY), 12, 167–169. [Google Scholar]
- Pinto J, Lynd A, Elissa N, Donnelly MJ, Costa C, Gentile G, Caccone A, do Rosário VE. 2006. Co-occurrence of East and West African kdr mutations suggests high levels of resistance to pyrethroid insecticides in Anopheles gambiae from Libreville, Gabon. Medical and Veterinary Entomology, 20, 27–32. [Google Scholar]
- Poungou N, Sevidzem SL, Koumba AA, Koumba CRZ, Mbehang P, Onanga R, Zahouli JZB, Maganga GD, Djogbénou LS, Borrmann S. 2023. Mosquito-borne arboviruses occurrence and distribution in the last three decades in Central Africa: a systematic literature review. Microorganisms, 12, 4. [Google Scholar]
- Rezza G, Nicoletti L, Angelini R, Romi R, Finarelli AC, Panning M, Cordioli P, Fortuna C, Boros S, Magurano F. 2007. Infection with chikungunya virus in Italy: an outbreak in a temperate region. Lancet, 370, 1840–1846. [Google Scholar]
- Roiz D, Wilson AL, Scott TW, Fonseca DM, Jourdain F, Müller P, Velayudhan R, Corbel V. 2022. Correction: Integrated Aedes management for the control of Aedes-borne diseases. PLoS Neglected Tropical Diseases, 16, e0010310. [Google Scholar]
- Seid M, Aklilu E, Animut A. 2024. Susceptibility status of Aedes aegypti (Diptera: Culicidae) to public health insecticides in Southern Afar Region, Ethiopia. PLoS One, 19, e0309335. [Google Scholar]
- Sene NM, Mavridis K, Ndiaye EH, Diagne CT, Gaye A, Ngom EHM, Ba Y, Diallo D, Vontas J, Dia I, Diallo M. 2021. Insecticide resistance status and mechanisms in Aedes aegypti populations from Senegal. PLoS Neglected Tropical Diseases, 15, e0009393. [Google Scholar]
- Smith LB, Kasai S, Scott JG. 2016. Pyrethroid resistance in Aedes aegypti and Aedes albopictus: Important mosquito vectors of human diseases. Pesticide Biochemistry and Physiology, 133, 1–12. [Google Scholar]
- Socha W, Kwasnik M, Larska M, Rola J, Rozek W. 2022. Vector-borne viral diseases as a current threat for human and animal health – one health perspective. Journal of Clinical Medicine, 11, 3026. [Google Scholar]
- Sprenger PRD, Reiter D. 1987. The used tire trade: a mechanism for the worldwide dispersal of container breeding mosquitoes. Journal of the American Mosquito Control Association, 3, 494. [PubMed] [Google Scholar]
- Susanna D, Pratiwi D. 2021. Current status of insecticide resistance in malaria vectors in the Asian countries: a systematic review. F1000Research, 10, 200. [Google Scholar]
- Van Dyk JS, Pletschke B. 2011. Review on the use of enzymes for the detection of organochlorine, organophosphate and carbamate pesticides in the environment. Chemosphere, 82, 291–307. [CrossRef] [PubMed] [Google Scholar]
- Weetman D, Kamgang B, Badolo A, Moyes CL, Shearer FM, Coulibaly M, Pinto J, Lambrechts L, McCall PJ. 2018. Aedes mosquitoes and Aedes-borne arboviruses in Africa: Current and future threats. International Journal of Environmental Research and Public Health, 15, 220. [Google Scholar]
- WHO. 2022. Manual for monitoring insecticide resistance in mosquito vectors and selecting appropriate interventions. World Health Organization: Geneva, Switzerland. [Google Scholar]
- Yougang AP, Kamgang B, Tedjou AN, Wilson-Bahun TA, Njiokou F, Wondji CS. 2020. Nationwide profiling of insecticide resistance in Aedes albopictus (Diptera: Culicidae) in Cameroon. PLoS One, 15, e0234572. [Google Scholar]
- Yougang AP, Keumeni CR, Wilson-Bahun TA, Tedjou AN, Njiokou F, Wondji C, Kamgang B. 2022. Spatial distribution and insecticide resistance profile of Aedes aegypti and Aedes albopictus in Douala, the most important city of Cameroon. PLoS One, 17, e0278779. [Google Scholar]
- Zulfa R, Lo W-C, Cheng P-C, Martini M, Chuang T-W. 2022. Updating the insecticide resistance status of Aedes aegypti and Aedes albopictus in Asia: A systematic review and meta-analysis. Tropical Medicine and Infectious Disease, 7, 306. [Google Scholar]
Cite this article as: Obame-Nkoghe J, Moudoumi Kondji F, Diouf EH, Thiaw O, Niangui BG, Ondo-Oyono A, Okomo-Nguema Y, Longo-Pendy NM, Mounioko F, Makanga B, Kamgang B, Paupy C, Kengne P, Voua Otomo P & Niang EHA. 2025. Bioassay tests reveal for the first time pyrethroid resistance in Aedes mosquitoes from Franceville, southeast Gabon, Central Africa. Parasite 32, 40. https://doi.org/10.1051/parasite/2025036.
All Tables
All Figures
![]() |
Figure 1 Localisation of Franceville. |
In the text |
![]() |
Figure 2 Mortality of adult females 24 h after 1-hour exposure to insecticides and pre-exposure to PBO. The red dotted line indicates 90% mortality, and the green one 98% mortality. |
In the text |
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.