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Zika virus (ZIKV) is an arbovirus that has dramatically spread in South America and the Caribbean regions since 2015. The majority of vector incrimination studies available for ZIKV showed that Aedes aegypti mosquitoes are important vectors for this virus. However, several reports suggest that Culex quinquefasciatus mosquitoes may be implicated in ZIKV transmission in certain urban settings. In the present study, we evaluated the vector competence for ZIKV of Cx. quinquefasciatus and Ae. aegypti mosquitoes from Guadeloupe using African, American and Asian strains. The results demonstrated that Cx. quinquefasciatus is refractory to ZIKV infection whatever the strain tested at 7, 14 or 21 days post-infection (dpi), while ZIKV transmission was recorded in Ae. aegypti for all the three strains. The African ZIKV strain was better transmitted by Ae. aegypti (∼ 50% mean transmission efficiency) and with a shorter incubation period (7 dpi) when compared to the Asian and American strains (<14% transmission efficiency; incubation period of 14-21 dpi). Taken together, these results suggest that only Ae. aegypti mosquitoes are involved in urban ZIKV transmission in Guadeloupe and highlight a higher infectiousness of the African ZIKV strain in this mosquito species when compared to the Asian and American ones.

Rift Valley fever (RVF) is a vector-borne viral zoonosis of increasing global importance. RVF virus (RVFV) is transmitted either through exposure to infected animals or through bites from different species of infected mosquitoes, mainly of Aedes and Culex genera. These mosquitoes are very sensitive to environmental conditions, which may determine their presence, biology, and abundance. In East Africa, RVF outbreaks are known to be closely associated with heavy rainfall events, unlike in the semi-arid regions of West Africa where the drivers of RVF emergence remain poorly understood. The assumed importance of temporary ponds and rainfall temporal distribution therefore needs to be investigated. A hydrological model is combined with a mosquito population model to predict the abundance of the two main mosquito species (Aedes vexans and Culex poicilipes) involved in RVFV transmission in Senegal. The study area is an agropastoral zone located in the Ferlo Valley, characterized by a dense network of temporary water ponds which constitute mosquito breeding sites. The hydrological model uses daily rainfall as input to simulate variations of pond surface areas. The mosquito population model is mechanistic, considers both aquatic and adult stages and is driven by pond dynamics. Once validated using hydrological and entomological field data, the model was used to simulate the abundance dynamics of the two mosquito species over a 43-year period (1961-2003). We analysed the predicted dynamics of mosquito populations with regards to the years of main outbreaks. The results showed that the main RVF outbreaks occurred during years with simultaneous high abundances of both species. Our study provides for the first time a mechanistic insight on RVFV transmission in West Africa. It highlights the complementary roles of Aedes vexans and Culex poicilipes mosquitoes in virus transmission, and recommends the identification of rainfall patterns favourable for RVFV amplification.

Urbanization processes are increasing globally. Anthropogenic alterations in the environment have profound effects on biodiversity. Decreased biodiversity due to biotic homogenization processes as a consequence of urbanization often result in increased levels of mosquito vector species and vector-borne pathogen transmission. Understanding how anthropogenic alterations in the environment will affect the abundance, richness, and composition of vector mosquito species is crucial for the implementation of effective and targeted mosquito control strategies. We hypothesized that anthropogenic alterations in the environment are responsible for increasing the abundance of mosquito species that are adapted to urban environments such as Aedes aegypti and Culex quinquefasciatus . Therefore, our objective was to survey mosquito relative abundance, richness, and community composition in Miami-Dade County, Florida, in areas with different levels of urbanization. We selected 24 areas, 16 remote areas comprised of natural and rural areas, and 8 urban areas comprised of residential and touristic areas in Miami-Dade County, Florida. Mosquitoes were collected weekly in each area for 24 h for 5 consecutive weeks from August to October 2020 using BG-Sentinel traps baited with dry ice. A total of 36,645 mosquitoes were collected, from which 34,048 were collected in the remote areas and 2,597 in the urban areas. Our results show a clear and well-defined pattern of abundance, richness, and community composition according to anthropogenic modifications in land use and land cover. The more urbanized a given area the fewer species were found and those were primary vectors of arboviruses, Ae. aegypti and Cx. quinquefasciatus .

The efficacy of 30 aromatic compounds and their mutual binary combinations was assessed for acute toxicity against the larvae Culex quinquefasciatus. Based on comparison of the lethal doses, thymol and p-cymene were selected as the most effective (LD50 = 18 and 21 mg L−1, respectively, and LD90 = 25 and 30 mg L−1, respectively). Although the LD50 for terpinolene and trans-anethole was also estimated at 21 mg L−1, their LD90 was significantly higher compared to the substances above (245 and 34 mg L−1, respectively). In total, 435 binary combinations were tested, of which 249 combinations showed a significant synergistic effect, while 74 combinations showed a significant antagonistic effect on mortality. Only nine substances were identified as being able to create a synergistic effect with more than 20 substances: limonene, trans-anethole, 4-allylanisole, carvacrol, isoeugenol, menthone, carvone, borneol, and camphor. The highest synergistic effect on larval mortality was achieved for the combinations: eugenol and isoeugenol, carvone and carvacrol, carvone and 4-allylanisole, carvone and α-terpineol, carvone and menthone, limonene and trans-anethole, limonene and menthone, α-pinene and menthone, β-citronellol and menthone, carvacrol and 4-allylanisole, carvacrol and terpineol, α-terpinene and trans-anethole, camphor and menthone, camphene and menthone, and 4-allylanisole and menthone. Significant differences between achieved mortality and the mutual mixing ratio were found for the five selected binary mixtures that had shown the most significant synergistic effect in the previous tests. The mixture of limonene and trans-anethole showed the highest mortality, with the mixing ratio 1:1; the mixture of eugenol and isoeugenol caused 90.2 % mortality, with the mixing ratio 1:3. One hundred percent mortality was achieved if carvacrol was contained in a mixture with carvone in a ratio >2. After a comparison of all our results, based on our experiments, we can choose two pairs that caused mortality higher than 90 % in concentrations lower than 20 mg L−1: limonene and trans-anethole (with the mixing ratio 1:1), and carvone and carvacrol (with the mixing ratio 1:2–3). The information gained can thus be used in the development of new botanical insecticides based on essential oils (EOs) and particularly in the creation of formulations.

Various vector control strategies are in place to reduce the spread of arthropod-borne viruses. Some of these, such as application of insecticides, are encountering operational challenges and a reduced overall effectiveness due to evolution of resistance. Alternative approaches for mosquito population control, such as the sterile insect technique, depend on efficient mass-rearing of healthy mosquitoes prior to mass-release in the field. Therefore, improving efficiency and quality of mass-rearing techniques is crucial to obtain fit mosquitoes. Previous studies have shown that Acetic Acid Bacteria of the genus Asaia can have a mutualistic effect on larval development in different mosquito species and can thus contribute to improved rearing output. However, whether improved performance in the larval stages may have knock-on effects in the adult stage, for example by increasing their capability to transmit arbovirus, remains unclear. Such effects may jeopardize future control efforts. We tested the effects of two Asaia species, Asaia krungthepensis and Asaia bogorensis, on development time and adult size under two rearing conditions: individual rearing and group rearing of Culex pipiens larvae. Besides investigating development and size, we also investigated whether Asaia spp. exposure during the larval stage can influence the vector competence of Culex pipiens pipiens for West Nile virus (WNV). Our work shows the potential of improving mass-rearing efficiency by employing Asaia krungthepensis as a mutualist for Culex pipiens pipiens . Importantly, this study reveals no significant increase in dissemination and transmission rate of WNV by Culex pipiens pipiens when inoculated with Asaia spp., although an increase in viral titer in the legs and the saliva was observed when the mosquitoes were inoculated with the two Asaia species. Interestingly, we confirmed that Asaia spp . bacteria did not establish as a permanent member of the microbiota of Culex pipiens pipiens. As Asaia spp. did not establish in adult mosquitoes, the observed change in WNV titers can be a result of indirect interactions of Asaia with the native Culex pipiens pipiens microbiome. Our results stress the importance of carefully evaluating host-symbiont interactions to avoid the potential of releasing mosquitoes with enhanced vector competence.

Culex quinquefasciatus Say is a mosquito distributed in both tropical and subtropical regions of the world. It is a night-active, opportunistic blood-feeder and vectors many animal and human diseases, including West Nile Virus and avian malaria. Current vector control methods (e.g. physical/chemical) are increasingly ineffective; use of insecticides also imposes hazards to both human and ecosystem health. Advances in genome editing have allowed the development of genetic insect control methods, which are species-specific and, theoretically, highly effective. CRISPR/Cas9 is a bacteria-derived programmable gene editing tool that is functional in a range of species. We describe the first successful germline gene knock-in by homology dependent repair in C. quinquefasciatus . Using CRISPR/Cas9, we integrated an sgRNA expression cassette and marker gene encoding a fluorescent protein fluorophore (Hr5/IE1-DsRed, Cq7SK-sgRNA) into the kynurenine 3-monooxygenase ( kmo ) gene. We achieved a minimum transformation rate of 2.8%, similar to rates in other mosquito species. Precise knock-in at the intended locus was confirmed. Insertion homozygotes displayed a white eye phenotype in early-mid larvae and a recessive lethal phenotype by pupation. This work provides an efficient method for engineering C. quinquefasciatus , providing a new tool for developing genetic control tools for this vector.

Specific information about the dispersion of Culex quinquefasciatus from Dschang in western Cameroon is scarce, and evidence-based interventions are needed. Common use of larvicides and adulticides conduct to the development of vectors resistance which can lead to deep biological changes, including fitness costs. We assessed the profile of insecticide resistance in field populations of Cx. quiquefasciatus and its potential fitness cost in a lineage selected for deltamethrin and permethrin resistance in the laboratory for two generations. The resistance intensity of the Cx. quinquefasciatus population was moderated when the population was exposed to deltamethrin at 10 × . Preexposure to PBO led to the restoration of full susceptibility to both deltamethrin and permethrin. Compared with that of the control group, female fecundity rates, egg hatchability, and pupation rates were significantly lower in the insecticide exposed groups. Larval development time and adults emergence rates were comparable between insecticide-exposed groups and the control. Insecticide-exposed adults lived longer than control adults did. Our findings suggest that the mechanisms selected for pyrethroid resistance are associated with negative impacts on different life-trait parameters and support the hypothesis that insecticide resistance is related to a high fitness cost.

Mosquitoes, one of the deadliest animals on the planet, cause millions of fatalities each year by transmitting several human illnesses. Synthetic pesticides were previously used to prevent the spread of diseases by mosquitoes, which was effective in protecting humans but caused serious human health problems, environmental damage, and developed mosquito pesticide resistance. This research focuses on exploring new, more effective, safer, and environmentally friendly compounds to improve mosquito vector management. Phytochemicals are possible biological agents for controlling pests and many are target-specific, rapidly biodegradable, and eco-friendly. The potential of extracts of Lantana camara, Melia azedarach, Nerium oleander, Ricinus communis, and Withania somnifera against 3rd instar Culex pipiens (Common house mosquito) larvae was evaluated. Methanol extracts had more toxic effects against Cx. pipiens larvae (95–100%, 24 h post-treatment) than aqueous extracts (63–91%, 24 h post-treatment). The methanol extracts of Nerium oleander (LC 50  = 158.92 ppm) and Ricinus communis (LC 50  = 175.04 ppm) were very effective at killing mosquito larvae, 24 h after treatment. N. oleander (LC 50  = 373.29 ppm) showed high efficacy in aqueous plant extracts. Among the different extracts of the five plants screened, the methanol extract of R. communis recorded the highest ovicidal activity of 5% at 800 ppm concentration. Total developmental duration and growth index were highly affected by R. communis and M. azedarach methanol extracts. In field tests it was clear that plant extracts decreased mosquito larval density, especially when mixed with mosquito Bti briquette, with stability up to seven days for N. oleander . GC–MS results showed that the methanol extract had a higher number of chemical compounds, particularly with more terpene compounds. A high-performance liquid chromatography (HPLC) technique was used to detect the existence of non-volatile polyphenols and flavonoids. All five methanol extracts showed high concentrations of active ingredients such as gallic acid, chlorogenic acid (more than 100 μg/ml) and the rosmarinic acid was also found in all the five extracts in addition to 17 active polyphenols and flavonoids presented at moderate to low concentrations. Molecular modeling of 18 active ingredients detected by the HPLC were performed to the vicinity of one of the fatty acid binding proteins of lm -FABP (PDB code: 2FLJ ). Rutin, Caffeic acid, coumaric acid and rosmarinic acid which presented densely in R. communis and N. oleander showed multiple and stable intermolecular hydrogen bonding and π–π stacking interactions. The inhibition ability of the fatty acid binding protein, FABP4, was evaluated with remarkable receptor inhibition evident, especially with R. communis and N. oleander having inhibitory concentrations of IC 50  = 0.425 and 0.599 µg/mL, respectively. The active phytochemical compounds in the plants suggest promising larvicidal and ovicidal activity, and have potential as a safe and effective alternative to synthetic insecticides.

Mosquitoes are well known for their ability to transmit pathogens, including various arthropod-borne viruses (arboviruses) of veterinary and medical interest. In Europe, the increasing public health relevance of mosquito-borne pathogens highlights the need to understand how environmental drivers shape mosquito population dynamics relevant to transmission risk. Culex pipiens sensu stricto (s.s.) and Culex torrentium (collectively referred to here as Cx. pipiens s.s./Cx. torrentium) are the primary vectors of Usutu virus and West Nile virus in Europe and are commonly found in and around human settlements. The prediction of their spatial-temporal abundance supports early assessment of arbovirus transmission risk and the planning of effective intervention methods, such as vector control. A process-based model was developed to simulate the spatial-temporal occurrence of Cx. pipiens s.s./Cx. torrentium in Germany, with a particular focus on depicting realistic overwintering behaviour, including, diapause induced through photoperiod and temperature in the larval stage. The model output is driven by local temperature and rainfall data provided by the European re-analysis and observations for monitoring data set and evaluated with field data from 106 sampling sites in Germany. A significant association between relative simulated and observed mosquito abundance was found for 75% of the sampling sites, using site-specific beta regression models. An overall beta mixed-effects model across all sites was also significant (estimate = 2.17, standard error = 0.062, Z-value = 35.03, p-value < 0.0001, marginal R = 0.4). This model offers a robust framework for the depiction of the mosquito population dynamics of Cx. pipiens s.s./Cx. torrentium under current and future climate scenarios, thereby supporting vector surveillance and control strategies across Europe.

Mosquito control is a favorable strategy to prevent mosquito-borne diseases. There are various approaches for the management of potentially dreadful mosquito populations such as larvicides and adulticides. In this study, a series of novel benzochromene derivatives were synthesized and evaluated for their insecticidal efficacy against larvae and adult stages of Culex pipiens L. The synthesized compounds underwent comprehensive structural characterization and toxicological evaluation, revealing their larvicidal and adulticidal activity for several derivatives. The tested compounds were more effective against larvae than adults of C. pipiens . Compounds 10 and 5 exhibited pronounced larvicidal activity, surpassing the reference compound temephos, with LC₅₀ values of 40.15 and 46.17 ppm, respectively. In addition, both compounds displayed remarkable adulticidal efficacy, with LC₅₀ values of 55.02 and 65.43 ppm, respectively, whereas compound 6 showed the lowest potency among the tested series with LC₅₀ value of 215.40 ppm. Notably, compounds 10 and 5 were 5.36- and 4.66-fold more active against larvae than compound 6 , and demonstrated 5.28- and 4.44-fold higher adulticidal efficiency compared with deltamethrin. In cytotoxicity assays, compound 5 displayed an IC₅₀ value of 72.65 µM, while compound 10 showed an IC₅₀ of 90.32 µM, indicating low toxicity toward normal human cells and a favorable selectivity index. Molecular docking supported this observation by demonstrating strong and specific binding interactions with Anopheles gambiae acetylcholinesterase (AChE). Additionally, the DFT results provided insights into the electronic properties and stability of the compounds, while MEP mapping highlighted key reactive sites associated with target interactions. Structure–activity relationship (SAR) studies identified crucial functional groups influencing insecticidal potency.