Adult Aedes Mosquitoes Research Articles

Risk of arboviral transmission and insecticide resistance status of Aedes mosquitoes during a yellow fever outbreak in Ghana

BackgroundIn late 2021, Ghana was hit by a Yellow Fever outbreak that started in two districts in the Savannah region and spread to several other Districts in three regions. Yellow fever is endemic in Ghana. However, there is currently no structured vector control programme for Aedes the arboviral vector in Ghana. Knowledge of Aedes bionomics and insecticide susceptibility status is important to control the vectors. This study therefore sought to determine Aedes vector bionomics and their insecticide resistance status during a yellow fever outbreak.MethodsThe study was performed in two yellow fever outbreak sites (Wenchi, Larabanga) and two non-outbreak sites (Kpalsogu, Pagaza) in Ghana. Immature Aedes mosquitoes were sampled from water-holding containers in and around human habitations. The risk of disease transmission was determined in each site using stegomyia indices. Adult Aedes mosquitoes were sampled using Biogents Sentinel (BG) traps, Human Landing Catch (HLC), and Prokopack (PPK) aspirators. Phenotypic resistance to permethrin, deltamethrin and pirimiphos-methyl was determined with WHO susceptibility tests using Aedes mosquitoes collected as larvae and reared into adults. Knockdown resistance (kdr) mutations were detected using allele-specific multiplex PCR.ResultsAmong the 2,664 immature Aedes sampled, more than 60% were found in car tyres. Larabanga, an outbreak site, was classified as a high-risk zone for the Yellow Fever outbreak (BI: 84%, CI: 26.4%). Out of 1,507 adult Aedes mosquitoes collected, Aedes aegypti was the predominant vector species (92%). A significantly high abundance of Aedes mosquitoes was observed during the dry season (61.2%) and outdoors (60.6%) (P < 0.001). Moderate to high resistance to deltamethrin was observed in all sites (33.75% to 70%). Moderate resistance to pirimiphos-methyl (65%) was observed in Kpalsogu. Aedes mosquitoes from Larabanga were susceptible (98%) to permethrin. The F1534C kdr, V1016I kdr and V410 kdr alleles were present in all the sites with frequencies between (0.05–0.92). The outbreak sites had significantly higher allele frequencies of F1534C and V1016I respectively compared to non-outbreak sites (P < 0.001).ConclusionThis study indicates that Aedes mosquitoes in Ghana pose a significant risk to public health. Hence there is a need to continue monitoring these vectors to develop an effective control strategy.

Mass irradiation of adult Aedes mosquitoes using a coolable 3D printed canister

In the last decade, the use of the sterile insect technique (SIT) to suppress mosquito vectors have rapidly expanded in many countries facing the complexities of scaling up production and procedures to sustain large-scale operational programs. While many solutions have been proposed to improve mass production, sex separation and field release procedures, relatively little attention has been devoted to effective mass sterilization of mosquitoes. Since irradiation of pupae en masse has proven difficult to standardise with several variables affecting dose response uniformity, the manipulation of adult mosquitoes appears to be the most promising method to achieve effective and reliable sterilization of large quantities of mosquitoes. A 3D-printed phase change material based coolable canister was developed which can compact, immobilize and hold around 100,000 adult mosquitoes during mass radio sterilization procedures. The mass irradiation and compaction treatments affected the survival and the flight ability of Aedes albopictus and Aedes aegypti adult males but the use of the proposed irradiation canister under chilled conditions (6.7–11.3 °C) significantly improved their quality and performance. The use of this cooled canister will facilitate adult mass irradiation procedures in self-contained irradiators in operational mosquito SIT programmes.

Distribution and Abundance of Aedes aegypti and Aedes albopictus (Diptera: Culicidae) in Benin, West Africa.

Updated information on the distribution and abundance of Aedes aegypti and Aedes albopictus is crucial to prepare African countries, such as Benin, for possible arboviral disease outbreaks. This study aims to evaluate the geographical distribution, abundance and biting behaviour of these two vectors in Benin. Three sampling techniques were used in this study. The collection of Aedes spp. adults were made through human landing catch (HLC), immatures were captured with the use of ovitraps, and a dipping technique was used for the collection of Aedes spp. in 23 communes located along the North-South and East-West transect of Benin. Adult Aedes mosquitoes were collected indoors and outdoors using HLC. Mosquito eggs, larvae and pupae were collected from containers and ovitraps. The adult mosquitoes were morphologically identified, then confirmed using a polymerase chain reaction (PCR). Overall, 12,424 adult specimens of Aedes spp. were collected, out of which 76.53% (n = 9508) and 19.32% (n = 2400) were morphologically identified as Ae. aegypti and Ae. albopictus, respectively. Geographically, Ae. aegypti was found across the North-South transect unlike Ae. albopictus, which was only encountered in the southern part of the country, with a great preponderance in Avrankou. Furthermore, an exophagic behaviour was observed in both vectors. This updated distribution of Aedes mosquito species in Benin will help to accurately identify areas that are at risk of arboviral diseases and better plan for future vector control interventions.

The Density of Aedes albopictus in a High-Latitude and High-Risk Dengue Fever Transmission Region in Shandong Province, Northern China.

Background: A total of 79 cases of dengue fever were reported in Jining County in 2017, which is currently the northernmost focal point of local cases of dengue fever diagnosed in China. This study aimed to evaluate the density of mosquito vectors before and after the outbreak of dengue fever and provide novel reference data for the prevention and control of the disease. Methods: The light traps were set to collect mosquitoes in 2017 and 2018 to assess adult mosquito density and species composition. We used the human-baited double net trap to determine the biting rate. In addition, the Breteau index (BI) was calculated to evaluate the density of Aedes albopictus in Jining, Shandong Province. The annual average densities of Ae. albopictus in 2017 and 2018 were 0.046 and 0.066 f/t/h, respectively. Results: The average biting rate was 0.69 f/m/h in 2018. There was no significant difference found in Ae. albopictus density and biting rate in the various months. The average BI of Jining was 38.67 and 11.17, respectively. There was a statistically significant difference observed in the BI between 2017 and 2018 (Kruskal-Wallis test, χ2 = 16.926, df = 1, p < 0.001). Conclusion: BI can serve as an important indicator to determine the spread of dengue fever. The findings indicted that the growing density of adult Aedes mosquitoes should be focused on, with biting rates being a potential indicator of future outbreaks. Overall, the various control measures that were implemented were effective and should be introduced in other high-risk areas.

Susceptibility status of Aedes aegypti (Diptera: Culicidae) against insecticides of public health use in Delhi and NCR region, India.

Aedes (Stegomyia) aegypti is a primary vector responsible for the transmission of various arboviral diseases in India. Without an effective drug or vaccine against these diseases, chemical insecticide-based vector control supplemented with source reduction remains the best option for their effective management. The development of insecticide resistance due to the continuous use of insecticides might affect the control operations. Adults and larvae of Aedes aegypti were collected from different localities in Delhi. Larvae were exposed to discriminating (0.02mg/l) and application (1mg/l) doses of temephos. WHO tube assay was conducted for F1 adults using impregnated insecticide papers of dichlorodiphenyltrichloroethane (DDT), malathion, deltamethrin, permethrin, cyfluthrin, and lambda-cyhalothrin. Larvae of Ae. aegypti were found resistant (76.0%) to the discriminating dose of temephos, whereas suscep-tible (100.0%) to the application dose of the temephos. Adult Aedes (Fl) mosquitoes were resistant to DDT (23.7%), malathion (90.5%), deltamethrin (76.0%), permethrin (96.2 %) cyfluthrin (85.5%), and lambda-cyhalothrin (94.0%). Indoor residual spray is not used in Delhi for vector control. Resistance in Aedes might be due to pesticide usage for agricultural activities in peripheral regions of Delhi. There is a need to investigate more on the insecticide resistance mechanisms for indirect resistance development. Understanding the insecticide susceptibility status of urban vectors is critical for planning effective control strategies.

A Mathematical Formulation for Control the Transmission of Dengue Disease

It is transmitted between people by the bite of female adult Aedes mosquitoes. In the present work, we study a mathematical modling which work as a powerful tool for controlling the dengue disease. The aim of the study is to observe the effects of control measures on the dengue disease development. Explicit formula for the metric, basic reproduction number 0 is obtained using Next Generation Matrix method. Stability of the disease free equilibrium and sensitivity analysis of model's parameters are discussed in terms of basic reproduction number. It is observed that the disease free equilibrium is locally and globally stable when 0 &lt; 1 and unstable when 0 &gt; 1. Numerical results are carried out to illustrate the impact of control measures in the disease transmission. We know the effect of our model on lead &amp; also at global level. Dengue is a masquito–borne viral infection that is usually found in tropical &amp; sub–tropical regions around the world. In recent years, transmission has increased pro–dominantly in urban &amp; semi urban areas &amp; has become a major public health cancern

Effects of Chilling and Anoxia on the Irradiation Dose-Response in Adult Aedes Mosquitoes.

The success of the sterile insect technique (SIT) relies on the achievement of high levels of sterility and mating success of the factory-reared sterile males and thus their biological quality, which can be enhanced by the reduction of stress factors encountered during rearing, handling, and irradiation procedures. The achievement of consistent sterility levels requires reliable and standard irradiation protocols. Additionally, mosquito adults require immobilization prior to, and during irradiation to increase processing efficiency and to avoid physical damage caused by movement in restricted space. Common methods for immobilization include chilling and anesthetics such as nitrogen. Here we assessed the effects of chilling and exposure to nitrogen on the irradiation dose-response of Aedes mosquitoes, and their downstream effects on some male quality parameters including longevity and flight ability. We found that chilling does not incur damage in the insects in terms of longevity and flight ability when chilling duration and temperature are carefully controlled, and a recovery phase is provided. Irradiation in nitrogen shows high radioprotective effects during irradiation, resulting in reduced induction of sterility. Overall, longevity of males can be improved by irradiating in anoxia, however the exposure to nitrogen itself comes with negative impacts on flight ability. The results reported here will assist in the standardization and optimization of irradiation protocols for the SIT to control mosquito populations of medical relevance.

Evaluation of the efficacy of pyrethroid pesticides against selected strains of Aedes mosquitoes using the who susceptibility test and by thermal fogging

Tests on the efficacy of pyrethroid insecticides in fogging were conducted. These were done in two approaches: 1. A laboratory-based series of the WHO susceptibility tests on F1- generation female adult Aedes mosquitoes, and 2. A series of actual field thermal fogging using caged sentinel F1-generation Aedes mosquitoes. Based on the 98% WHO susceptibility test criterion, strains of Ae. Aegypti have shown to have incipient resistance to pyrethroids, making them less susceptible to laboratory and field tests. Ae. Albopictus was found susceptible to pyrethroids, but it requires further confirmatory tests based on field test results. The study recommends molecular tests on mechanisms involved, nationwide surveillance of susceptibility/resistance of dengue vector mosquitoes, and a review of the chemical control strategies used by authorities.

Spatiotemporal distribution and insecticide resistance status of Aedes aegypti in Ghana

BackgroundVector control is the main intervention used to control arboviral diseases transmitted by Aedes mosquitoes because there are no effective vaccines or treatments for most of them. Control of Aedes mosquitoes relies heavily on the use of insecticides, the effectiveness of which may be impacted by resistance. In addition, rational insecticide application requires detailed knowledge of vector distribution, dynamics, resting, and feeding behaviours, which are poorly understood for Aedes mosquitoes in Africa. This study investigated the spatiotemporal distribution and insecticide resistance status of Aedes aegypti across ecological extremes of Ghana.MethodsImmature mosquitoes were sampled from containers in and around human dwellings at seven study sites in urban, suburban, and rural areas of Ghana. Adult Aedes mosquitoes were sampled indoors and outdoors using Biogents BG-Sentinel 2 mosquito traps, human landing catches, and Prokopack aspiration. Distributions of immature and adult Aedes mosquitoes were determined indoors and outdoors during dry and rainy seasons at all sites. The phenotypic resistance status of Aedes mosquitoes to insecticides was determined using World Health Organization susceptibility bioassays. The host blood meal source was determined by polymerase chain reaction.ResultsA total of 16,711 immature Aedes were sampled, with over 70% found in car tyres. Significantly more breeding containers had Aedes immatures during the rainy season (11,856; 70.95%) compared to the dry season (4855; 29.05%). A total of 1895 adult Aedes mosquitos were collected, including Aedes aegypti (97.8%), Aedes africanus (2.1%) and Aedesluteocephalus (0.1%). Indoor sampling of adult Aedes yielded a total of 381 (20.1%) and outdoor sampling a total of 1514 (79.9%) mosquitoes (z = − 5.427, P = 0.0000) over the entire sampling period. Aedes aegypti populations were resistant to dichlorodiphenyltrichloroethane at all study sites. Vectors showed suspected resistance to bendiocarb (96–97%), permethrin (90–96%) and deltamethrin (91–96%), and were susceptible to the organophosphate for all study sites. Blood meal analysis showed that the Aedes mosquitoes were mostly anthropophilic, with a human blood index of 0.9 (i.e. humans, 90%; human and dog, 5%; dog and cow, 5%).ConclusionsAedes mosquitoes were found at high densities in all ecological zones of Ghana. Resistance of Aedes spp. to pyrethroids and carbamates may limit the efficacy of vector control programmes and thus requires careful monitoring.Graphicalabstract

Entomological outcomes of cluster-randomised, community-driven dengue vector-suppression interventions in Kampong Cham province, Cambodia.

Cambodia has one of the highest dengue infection rates in Southeast Asia. Here we report quantitative entomological results of a large-scale cluster-randomised trial assessing the impact on vector populations of a package of vector control interventions including larvivorous guppy fish in household water containers, mosquito trapping with gravid-ovitraps, solid waste management, breeding-container coverage through community education and engagement for behavioural change, particularly through the participation of school children. These activities resulted in major reductions in Container Index, House Index, Breteau Index, Pupal Index and Adult Index (all p-values 0.002 or lower) in the Intervention Arm compared with the Control Arm in a series of household surveys conducted over a follow-up period of more than one year, although the project was not able to measure the longer-term sustainability of the interventions. Despite comparative reductions in Adult Index between the study arms, the Adult Index was higher in the Intervention Arm in the final household survey than in the first household survey. This package of biophysical and community engagement interventions was highly effective in reducing entomological indices for dengue compared with the control group, but caution is required in extrapolating the reduction in household Adult Index to a reduction in the overall population of adult Aedes mosquitoes, and in interpreting the relationship between a reduction in entomological indices and a reduction in the number of dengue cases. The package of interventions should be trialled in other locations.

Efficacy of Intelligent Mosquito System (I.M.O.S) with Xmos Mini Aerosol Against Aedes in 17th College, Universiti Putra Malaysia

This study reports the efficacy of I.M.O.S (Intelligent Mosquito System) by using Xmos mini aerosol in reducing Aedes mosquito population in 17th College, Universiti Putra Malaysia (UPM). Prior to the experiment, the Aedes mosquito population was determined in all blocks of the 17th College, UPM. The I.M.O.S. was installed above the entrance door of the hall and two rooms and was set to automatically spray at 6.30 am and 4.00 pm every day. No intervention was used in the control house. Adult efficacy study was conducted by placing 20 Aedes mosquitoes in each cage and was hung at a distance of 10 feet from the I.M.O.S. The mortality caused by I.M.O.S throughout the exposed two hours and after 24 hours of exposure was recorded. The number mosquito eggs population were calculated throughout the installation of I.M.O.S. Data were analysed using two-way ANOVA and paired T-test, respectively. The mean number of Aedes mosquito eggs and ovitraps index showed no significant difference (p&gt;0.05) between control and treatment blocks. There were significant differences (p&lt;0.05) in the percentage of knockdown of adult Aedes mosquitoes (10, 20, 30, 60 and 120 minutes after exposure) and the mortality of adult Aedes mosquitoes after 24 hours exposure. Nano and slow-release technology of the I.M.O.S with Xmos mini aerosol proved that this type of intervention can kill adult Aedes mosquitoes. Thus, it is a potential intervention for vector control and management.

Arbovirus surveillance in the adult female Aedes mosquitoes of Hong Kong

Background: Hong Kong is a highly urbanized city yet retains a large proportion of protected natural areas. This environment has shaped the human-animal proximity and interaction, including the ecology of mosquitoes. Although Hong Kong is close to (130 km) Guangzhou that has periodically experienced severe dengue outbreaks since the record-breaking outbreak in 2014, relatively few dengue infections have been reported in Hong Kong, and almost all of which were imported cases. However, in the summer of year 2018, the largest ever dengue outbreak by local transmission occurred in Hong Kong, where 29 cases were reported from two infection clusters in Lion Rock Park and Cheung Chau Island. Since then increasing attentions have been placed on the potential risks underpinning the local transmissions of arbovirus by mosquitoes. Methods and materials: Our study presents by far the largest territory-wide cross-sectional surveillance of adult mosquitoes and their arboviruses in Hong Kong. Twenty sites, including those located in the urban parks, country parks and in the vicinity to animal farms were intensively sampled for adult mosquitoes on weekly basis during the summer of 2019. Results: Mosquitoes captured were taxonomically classified, where majority belong to Aedes family. PCR detection of arboviruses commonly transmitted by mosquitoes were performed. A putative flavivirus species was found in the preliminary testing. Metagenomic sequencing was also done to comprehensively study the virome in these mosquito populations in Hong Kong. Conclusion: This pilot study aims to describe the diversity landscape of the mosquito and arbovirus in Hong Kong, and identify the priority targets for the longitudinal surveillance in the future.

Interepidemic Detection of Chikungunya Virus Infection and Transmission in Northeastern Thailand

Chikungunya fever is a viral mosquito-borne, acute febrile illness associated with rash, joint pain, and occasionally prolonged polyarthritis. Chikungunya outbreaks have been reported worldwide including many provinces of Thailand. Although chikungunya virus (CHIKV) occurs in Thailand, details on its epidemiology are lacking compared with dengue, a common mosquito-borne disease in the country. Therefore, study on CHIKV and its epidemiology in both humans and mosquitoes is required to better understand its importance clinically and dynamics in community settings. So a prospective examination of virus circulation in human and mosquito populations in northeastern Thailand using serological and molecular methods, including the genetic characterization of the virus, was undertaken. The study was conducted among febrile patients in eight district hospitals in northeastern Thailand from June 2016 to October 2017. Using real-time PCR on the conserved region of nonstructural protein 1 gene, CHIKV was detected in eight (4.9%) of 161 plasma samples. Only one strain yielded a sequence of sufficient size allowing for phylogenetic analysis. In addition, anti-CHIKV IgM and IgG were detected in six (3.7%) and 17 (10.6%) patient plasma samples. The single sequenced sample belonged to the East/Central/South Africa (ECSA) genotype and was phylogenetically similar to the Indian Ocean sub-lineage. Adult Aedes mosquitoes were collected indoors and within a 100-m radius from the index case house and four neighboring houses. CHIKV was detected in two of 70 (2.9%) female Aedes aegypti mosquito pools. This study clearly demonstrated the presence and local transmission of the ECSA genotype of CHIKV in the northeastern region of Thailand.

Ability of the Premise Condition Index to Identify Premises with Adult and Immature Aedes Mosquitoes in Kampong Cham, Cambodia.

.Aedes-transmitted diseases, especially dengue, are increasing throughout the world and the main preventive methods include vector control and the avoidance of mosquito bites. A simple Premise Condition Index (PCI) categorizing shade, house, and yard conditions was previously developed to help prioritize households or geographical areas where resources are limited. However, evidence about the accuracy of the PCI is mixed. The current study aimed to contribute to a better understanding of the relevance by collecting data from 2,400 premises at four time points over 1 year in Kampong Cham, Cambodia. Regression models were then used to identify associations between PCI and Aedes adult female mosquitoes and pupae. In addition, receiver operating characteristic curves were used to measure the ability of PCI to identify premises in the top quartile of mosquito abundance. The density of adult Aedes females was positively associated with PCI at the household (ratio of means = 1.16 per point on the PCI scale) and cluster level (ratio of means = 1.54). However, the number of Aedes pupae was negatively associated with PCI at the household level (rate ratio = 0.74) and did not have a statistically significant association at the cluster level. Receiver operating characteristic curves suggest the PCI score had “rather low accuracy” (area under the ROC curve = 0.52 and 0.54) at identifying top-quartile premises in terms of adult female Aedes and pupae, respectively. These results suggest that caution is warranted in the programmatic use of PCI in areas of similar geography and mosquito abundance.

Incrimination of Aedes aegypti and Aedes albopictus as vectors of dengue virus serotypes 1, 2 and 3 from four states of Northeast India.

Dengue is an important vector borne disease with a great public health concern worldwide. Northeast India has experienced dengue almost every year for a decade. As studies on dengue vectors from this region are limited, we undertook an investigation to detect natural infection of the dengue virus (DENV) in potential dengue vectors of this region. Adult Aedes mosquitoes which were collected were subjected to RT-PCR for detection of infecting dengue serotype. Minimum infection rate was also determined for each positive pool. Out of the total 6229 adult Aedes mosquitoes collected, Aedes aegypti (63.3 %) was abundant in comparison to Aedes albopictus (36.7 %). These specimens (515 mosquito pools) were subjected to RT-PCR for detection of DENV-1, 2, 3 and 4. RT-PCR revealed the existence of DENV in both male as well as female mosquito pools suggesting natural transovarial transmission of DENV in this region. A total of 54 pools tested were positive for DENV-1, 2, 3 serotypes. This study revealed the occurence of DENV in both the potential dengue vectors from this region along with evidence of transovarial transmission which helps in persistence of the virus in nature.

Reducing the cost and assessing the performance of a novel adult mass-rearing cage for the dengue, chikungunya, yellow fever and Zika vector, Aedes aegypti (Linnaeus).

IntroductionThe widespread emergence of resistance to insecticides used to control adult Aedes mosquitoes has made traditional control strategies inadequate for the reduction of various vector populations. Therefore, complementary vector control methods, such as the Sterile Insect Technique, are needed to enhance existing efforts. The technique relies on the rearing and release of large numbers of sterile males, and the development of efficient and standardized mass-rearing procedures and tools is essential for its application against medically important mosquitoes.MethodsIn the effort to reduce the cost of the rearing process, a prototype low-cost plexiglass mass-rearing cage has been developed and tested for egg production and egg hatch rate in comparison to the current Food and Agriculture Organization/International Atomic Energy Agency (FAO/IAEA) stainless-steel cage. Additionally, an adult-index was validated and used as a proxy to estimate the mosquito survival rates by counting the number of male and female mosquitoes that were resting within each of the 6 squares at a given point of time each day in the cage.ResultsThe study has shown that the prototype mass-rearing cage is cheap and is as efficient as the FAO/IAEA stainless-steel cage in terms of egg production, with even better overall egg hatch rate. The mean numbers of eggs per cage, after seven cycles of blood feeding and egg collection, were 969,789 ± 138,101 and 779,970 ± 123,042, corresponding to 81 ± 11 and 65 ± 10 eggs per female over her lifespan, in the prototype and the stainless-steel-mass-rearing cages, respectively. The longevity of adult male and female mosquitoes was not affected by cage type and, the adult-index could be considered as an appropriate proxy for survival. Moreover, the mass-rearing cage prototype is easy to handle and transport and improves economic and logistic efficiency.ConclusionThe low-cost mass-rearing prototype cage can be recommended to produce Ae. aegypti in the context of rear and release techniques. The proposed adult-index can be used as a quick proxy of mosquito survival rates in mass-rearing settings.

Expression of Bacillus thuringiensis toxin Cyt2Ba in the entomopathogenic fungus Beauveria bassiana increases its virulence towards Aedes mosquitoes.

BackgroundThe entomopathogenic fungus Beauveria bassiana has been widely used to kill mosquito larvae and adults in the laboratory and field. However, its slow action of killing has hampered its widespread application. In our study, the B. bassiana fungus was genetically modified to express the Bacillus thuringiensis (Bt) toxin Cyt2Ba to improve its efficacy in killing mosquitoes.Methodology/Principal findingsThe efficacy of the wild type (WT) of B. bassiana and a transgenic strain expressing Cyt2Ba toxin (Bb-Cyt2Ba) was evaluated against larval and adult Aedes mosquitoes (Aedes aegypti and Aedes albopictus) using insect bioassays. The Bb-Cyt2Ba displayed increased virulence against larval and adult Aedes mosquitoes compared with the WT: for Ae. aegypti adults, the median lethal time (LT50) was decreased by 33% at the concentration of 1× 108 conidia/ml, 19% at 1× 107 conidia/ml and 47% at 1× 106 conidia/ml. The LT50 for Ae. albopictus adults was reduced by 20%, 23% and 29% at the same concentrations, respectively. The LT50 for Ae. aegypti larvae was decreased by 42% at 1× 107 conidia/ml and 25% at 1× 106 conidia/ml, and that for Ae. albopictus larvae was reduced by 33% and 31% at the same concentrations, respectively. In addition, infection with Bb-Cyt2Ba resulted in a dramatic reduction in the fecundity of Aedes mosquitoes.Conclusions/SignificanceIn conclusion, our study demonstrated that the virulence of B. bassiana against mosquitoes can be significantly improved by introducing the Bt toxin gene Cyt2Ba into the genome to express the exogenous toxin in the fungus. The transgenic strain Bb-Cyt2Ba significantly reduced the survival and fecundity of Ae. aegypti and Ae. albopictus compared with the WT strain, which suggested that this recombinant B. bassiana has great potential for use in mosquito control.

Trap Location and Premises Condition Influences on Aedes aegypti (Diptera: Culicidae) Catches Using Biogents Sentinel Traps During a 'Rear and Release' Program: Implications for Designing Surveillance Programs.

As the incidence of arboviral diseases such as dengue, Zika, chikungunya, and yellow fever increases globally, controlling their primary vector, Aedes aegypti (L.) (Diptera: Culicidae), is of greater importance than ever before. Mosquito control programs rely heavily on effective adult surveillance to ensure methodological efficacy. The Biogents Sentinel (BGS) trap is the gold standard for surveilling adult Aedes mosquitoes and is commonly deployed worldwide, including during modern 'rear and release' programs. Despite its extensive use, few studies have directly assessed environmental characteristics that affect BGS trap catches, let alone how these influences change during 'rear and release' programs. We assessed male and female Ae. aegypti spatial stability, as well as premises condition and trap location influences on BGS trap catches, as part of Debug Innisfail 'rear and release' program in northern Australia. We found similar trends in spatial stability of male and female mosquitoes at both weekly and monthly resolutions. From surveillance in locations where no males were released, reduced catches were found at premises that contained somewhat damaged houses and unscreened properties. In addition, when traps were located in areas that were unsheltered, more than 10 m from commonly used sitting areas or more visually complex catches were also negatively affected. In locations where males were released, we found that traps in treatment sites, relative to control sites, displayed increased catches in heavily shaded premises and were inconsistently influenced by differences in house sets and building materials. Such findings have valuable implications for a range of Ae. aegypti surveillance programs.

Distribution of dengue vectors, Aedes aegypti and Aedes albopictus, in a few selected semi-urban areas of the Central Province of Sri Lanka

Aedes aegypti and Aedes albopictus are the two major vectors transmitting dengue viruses. The current study was undertaken from October to November 2014 to identify the distribution of dengue vectors in the Akurana Medical Officer of Health (MOH) division, which consisted of Akurana, Dunuwila and Alawathugoda Public Health Inspector (PHI) divisions. Larvae were collected from potential breeding sites in randomly selected houses in the selected PHI areas. Aedes larvae were incubated to emerge and the adults were differentiated into species using morphological features. Adult Aedes mosquitoes were pooled and tested for NS1 antigen. The total larvae collected were 700 and the total number of emerged adults were 171, consisting of 116 A. albopictus and 55 A. aegypti mosquitoes. None of the Aedes pools tested were positive for dengue NS1. A. albopictus was found to be abundant in the Akurana MOH division during the study period.

Effects of desiccation stress on adult female longevity in Aedes aegypti and Ae. albopictus (Diptera: Culicidae): results of a systematic review and pooled survival analysis

BackgroundTransmission dynamics of mosquito-borne viruses such as dengue, Zika and chikungunya are affected by the longevity of the adult female mosquito. Environmental conditions influence the survival of adult female Aedes mosquitoes, the primary vectors of these viruses. While the association of temperature with Aedes mortality has been relatively well-explored, the role of humidity is less established. The current study’s goals were to compile knowledge of the influence of humidity on adult survival in the important vector species Aedes aegypti and Ae. albopictus, and to quantify this relationship while accounting for the modifying effect of temperature.MethodsWe performed a systematic literature review to identify studies reporting experimental results informing the relationships among temperature, humidity and adult survival in Ae. aegypti and Ae. albopictus. Using a novel simulation approach to harmonize disparate survival data, we conducted pooled survival analyses via stratified and mixed effects Cox regression to estimate temperature-dependent associations between humidity and mortality risk for these species across a broad range of temperatures and vapor pressure deficits.ResultsAfter screening 1517 articles, 17 studies (one in semi-field and 16 in laboratory settings) met inclusion criteria and collectively reported results for 192 survival experiments. We review and synthesize relevant findings from these studies. Our stratified model estimated a strong temperature-dependent association of humidity with mortality in both species, though associations were not significant for Ae. albopictus in the mixed effects model. Lowest mortality risks were estimated around 27.5 °C and 21.5 °C for Ae. aegypti and Ae. albopictus, respectively, and mortality increased non-linearly with decreasing humidity. Aedes aegypti had a survival advantage relative to Ae. albopictus in the stratified model under most conditions, but species differences were not significant in the mixed effects model.ConclusionsHumidity is associated with mortality risk in adult female Ae. aegypti in controlled settings. Data are limited at low humidities, temperature extremes, and for Ae. albopictus, and further studies should be conducted to reduce model uncertainty in these contexts. Desiccation is likely an important factor in Aedes population dynamics and viral transmission in arid regions. Models of Aedes-borne virus transmission may be improved by more comprehensively representing humidity effects.