For the few, not the many: local economic conditions constrain the large-scale management of invasive mosquitoes

Invasive mosquitoes are an emerging ecological and sanitary issue. Many factors have been suggested as drivers or barriers to their control, still no study quantified their influence over mosquito management by local authorities, nor their interplay with local economic conditions.We assessed how multiple environmental, sanitary, and socio-economic factors affected the engagement of municipalities in Italy (n = 7,679) in actions against Aedes albopictus, an invasive mosquito affecting human health and well-being, between 2000 and 2020.Municipalities are more prone to manage A. albopictus if more urbanized, in lowlands, with long infestation periods and close to outbreaks of Chikungunya, for which A. albopictus is a competent vector. Moreover, these variables were more strongly associated with management in municipalities with a high median income, and thus more economic resources. Only 25.5% of Italian municipalities approved regulations for managing A. albopictus, and very few of them were in Southern Italy, the most deprived area of the country.Our findings indicate that local economic conditions moderate the effect of other drivers of mosquito control and ultimately can lead to better management of A. albopictus. Thus, to ensure social justice, existing policies for managing the impacts of invasive vectors should explicitly address territorial inequalities by providing policymakers with adequate economic means.

The Effects of Boric Acid Sugar Bait on Wolbachia Trans-Infected Male Aedes albopictus (ZAP Males®) in Laboratory Conditions

The field release of Wolbachia trans-infected male mosquitoes, as well as the use of toxic sugar baits, is a novel and promising candidate technique for integrated mosquito management programs. However, the methods of action of the two techniques may not be complementary, because the Wolbachia method releases mosquitoes into the environment expecting a wild population reduction in subsequent generations while the toxic baits are intended to reduce the wild population by killing mosquitoes. This laboratory study was conducted to evaluate the effectiveness of boric acid toxic sugar baits on Wolbachia trans-infected male Aedes albopictus, relative to wild-type Ae. albopictus males. Wolbachia trans-infected (ZAP male®) and the wild-type Ae. albopictus males were exposed separately to 1% boric acid in a 10% sucrose solution in BugDorms. In the control test, the two groups were exposed to 10% sucrose solution without boric acid. Percent mortalities were counted for 24 h, 48 h and 72 h post exposure periods. The results show that 1% boric acid toxic sugar bait can effectively kill ZAP males under laboratory conditions, and the effectiveness was significantly higher after 24 h and 48 h, compared to wild-type male Ae. albopictus. This finding will help in planning and coordinating integrated mosquito management programs, including both Wolbachia trans-infected mosquito releases and the use of toxic sugar baits against Ae. albopictus.

Multifunctional activity of graphene oxide-based nanoformulation against the disease vector, Aedes aegypti

Aedes aegypti management is a global concern due to the absence of medication and effective vaccines. The pesticide-mediated health hazards and rising insecticide resistance in mosquitoes have aggravated the issues. As graphene Oxide (GO)- based nanoformulations are considered a novel mosquito management strategy; the present investigation evaluated the efficacy of GO-based nanoformulations conjugated with malathion (ML) and endosulphan (EN) against Ae. aegypti. The GO was synthesised by Hummers’ method and was confirmed by UV-visible spectral analysis. The GO-ML and GO-EN binary mixtures (1:1 and 1:2) were assayed for toxic potential against mosquito larvae as per WHO protocol and the dead larvae were scrutinized for morphological deformations/abnormalities. The contact irritancy potential of GO nanoformulations was also evaluated against adult Ae. aegypti. The UV-visible spectrum of GO showed a narrow and high peak at ~300 nm corresponding to an n-π* plasmon peak. The GO-insecticide binary mixtures augmented the ML and EN toxicity by 80.43% and 6.43-fold, respectively. The GO-ML mixture-exposed larvae revealed cuticular deposition of black soot while larvae exposed to GO-EN exhibited disintegrated gut viscera. GO-insecticide combinations increased flights in Ae. aegypti denoting irritant potential. The effectual toxic, abrasive and irritant activity of GO-insecticide nanoformulations recommends developing graphene-based toxicants for mosquito management

Response of Mosquitoes Associated with Estuarine Wetlands to Bushfire in Australia

ABSTRACT The response of mosquitoes to bushfire is poorly understood. During the 2019–20 summer, many regions of Australia were impacted by devastating bushfires. An area of estuarine and brackish-water wetlands alongside the Georges River, Sydney, New South Wales, was burned in January 2020. Mosquito populations within the area were monitored as part of the local authority's mosquito management program, providing a unique opportunity to record the response of key mosquitoes of pest and public health concern to bushfire. Ground pools within a tidally influenced swamp oak forest dominated by Casuarina glauca and associated wetlands dominated by Phragmites australis and Bolboschoenus spp. had been identified as suitable habitat for a range of mosquitoes, including Aedes alternans, Ae. vigilax, and Verrallina funerea. Surveys of immature stages of mosquitoes within recently burned habitats inundated by tides demonstrated that mosquito eggs survived the direct and indirect impacts of fire and immature stages successfully completed development as reflected in concomitant changes in adult mosquito populations following the bushfire. This unique observation has implications for mosquito management following bushfire in Australia and internationally.

Susceptibility of South Texas Aedes aegypti to Pyriproxyfen

An integral part to integrated mosquito management is to ensure chemical products used for area-wide control are effective against a susceptible population of mosquitoes. Prior to conducting an intervention trial using an insect growth regulator, pyriproxyfen, in South Texas to control Aedes aegypti, we conducted a larval bioassay to evaluate baseline levels of susceptibility. We used seven serially-diluted doses ranging from 2.5 ppb to 6.3 × 10−4 ppb. We observed 100% inhibition emergence (IE) at even the lowest dose of 6.3 × 10−4 ppb in our susceptible reference colony of Ae. aegypti Liverpool. In our field strain of Ae. aegypti (F5 colonized from South Texas) we observed 79.8% IE at 6.3 × 10−4 ppb, 17.7% IE at 1.25 × 10−3 ppb, 98.7% IE at 1.25 × 10−2 ppb, and 100% emergence inhibition for the remainder of the doses. Given that commercial pyriproxyfen products are labeled for doses ranging to 50 ppb, we conclude that the field population sampled by this study are susceptible to this insect growth regulator.

SEMI-FIELD ULV EVALUATION OF AN ALL-PURPOSE BOTANICAL INSECTICIDE CONTAINING CEDARWOOD AND CINNAMON OILS AGAINST ADULT AEDES AEGYPTI

Public health mosquito control operates with only two classes of mosquito adulticides: pyrethroids and organophosphates. Recent work improving the emulsification of essential oils has increased the potential for development of plantderived active ingredients. There is a growing body of literature on essential oils for various roles in mosquito management. NatureCide Pest Management (NCPM), a product available in private and commercial home pest control, uses a mixture of 25.3% cedarwood oil and 12.7% cinnamon oil as a Federal Insecticide, Fungicide, Rodenticide Act (FIFRA) exempt insecticide for both indoor and outdoor use. Recent investigations by the Anastasia Mosquito Control District of St. Johns County have found other FIFRA exempt products to be effective as a residual spray on vegetation. In continuing the exploration of botanical insecticides, NCPM was used in ULV tests against Aedes aegypti (L.) within its 35-122 ml per L of water label rate. Applications at 35 ml/L resulted in 60-70% knockdown after 1 hr and mortality after 24 hr. Increasing the rate to 70 ml/L resulted in 100% knockdown and mortality across all replications. Crystalline precipitation of the microemulsion was observed in mix tanks after standing for at least 2 wk, but it was not apparent that the efficacy of the product was reduced as a consequence. Cedarwood oil and cinnamon oil are a beneficial combination for ULV adulticiding against mosquitoes and could have a beneficial role for integrated mosquito management.

Larvicidal Activity of Entomopathogenic Nematodes Isolated from Mexico against Aedes aegypti (Diptera: Culicidae)

Entomopathogenic nematodes (EPNs) are widely used agents of biological control, mainly targeting soil-inhabiting insect pests. Reports indicate that these terrestrial EPNs are also able to infect the aquatic larvae of mosquitoes. We isolated EPN strains (Heterorhabditis bacteriophora Poinar and Steinernema carpocapsae [Weiser]) from local soils at Saltillo, Coahuila state, Mexico. EPNs from these strains were produced in the laboratory in yellow mealworm (Tenebrio molitor L.) larvae, and their pathogenicity as infective juveniles (IJs) was tested against larvae of the yellow fever mosquito Aedes aegypti (L.) Third- and fourth-instar mosquito larvae were exposed to four concentrations of IJs (25, 50, 100, and 200 IJ/larva) of five strains of local EPNs in laboratory assays. All strains of EPN caused lethal infections in larvae (3–100%); in particular, strain M5 of S. carpocapsae caused 100% mortality at the 200 IJ/larva concentration, with a median lethal concentration (LC50) of 42 IJ/larva (LC90 = 91 IJ/larva). Strain M18 of H. bacteriophora caused 73% mortality at 200 IJ/larva, with an LC50 = 72 and LC90 = 319 IJ/larva. IJs were produced by all strains in mosquito larvae, with a range of 66–239 IJ/mosquito larva (inoculated at 100 IJ/larva) across strains, suggesting that horizontal transmission might occur in the field. This represents the first report of native EPN strains from Mexico exhibiting pathogenicity against mosquito larvae. Native EPN strains should be further evaluated as potential biological control agents in mosquito management.

Larvicidal Activity of Aqueous Pod Extract of Adansonia Digitata (Linnaeus, 1753) on Culex Quinquefasciatus (Say, 1823) Maulik

The study evaluatrd the effect of Baobab, Adansonia digitata pod extract on larvae of Culex quinquefaciatus. The plant material was sun-dried for two weeks and pulverized using mortar and pestle and stored at room temperature for further processes. Powdered plant material was extracted using aqueous cold extraction method. The condensed extract was screened for phytochemicals. Indoor resting adult blood-fed female Culex mosquitoes were collected and introduced into Entomological Cages in the Laboratory and oviposited on water in the bowls. The third instar larvae were confirmed as Cx. quinquefasciatus using Hopkins keys for Culicinae. Triplicates of twenty-five late third instar larvae were tested in pod extract concentrations of 0.5mg/L, 1.0mg/L, 1.5mg/L, 2.0mg/L and 2.50mg/L. Mortality was recorded after 24hr of exposure. The LC50 was determined using probit analysis, while one-way ANOVA was used to establish significant differences in larval mean mortality. Phytochemical constituents such as carbohydrate, cardiac glycosides, steroids, triterpenes, tannins, flavonoids and alkaloids were present. The mean mortality of test concentrations differed significantly (p≤0.05) from control. However, the concentrations: 0.5mg/L and 8.0mg/L had 49% and 71% mortalities, respectively with LC50 of 0.6mg/L. It can be concluded that, the aqueous pod extract of Adansonia digitata demonstrated good activity against Cx. quinquefasciatus. Adansonia digitata pod extracts has potential for controlling larvae of Culex mosquitoes and can be incorporated into integrated mosquito management programme.

Community participation and empowerment approaches to Aedes mosquito management in high-income countries: a scoping review

High-income countries (HICs) in sub-tropical and tropical regions are at an increasing risk of Aedes mosquito-borne disease (MBD) outbreaks such as dengue fever. As the Aedes mosquito predominately lives and breeds in and around people’s homes, community participation in MBD management is an important part of preventing MBD outbreaks. Historically, government-led strategies have dominated community participation efforts as opposed to strategies co-designed or led by the community. A scoping review was conducted to describe the community participation and empowering approaches used in Aedes mosquito management specifically in HICs, and to identify any reported outcomes of these methods. A systematic search of peer-reviewed literature using electronic databases Medline (OVID), Web of Science, Scopus and ProQuest—Science and Technology as well as grey literature, found 19 studies that matched the review criteria. The review findings highlight a lack of empirical evidence to inform participatory and empowering approaches to mosquito management in HICs. Moreover, the rationale for using predominantly government-led approaches is not clear. Further research is required to better understand best approaches and barriers to employing empowering approaches in mosquito management in HICs.