Local-scale virome depiction supports significant differences between Aedes aegypti and Aedes albopictus

Aedes spp. comprise the primary group of mosquitoes that transmit arboviruses such as dengue, Zika, and chikungunya viruses to humans, and thus these insects pose a significant burden on public health worldwide. Advancements in next-generation sequencing and metagenomics have expanded our knowledge on the richness of RNA viruses harbored by arthropods such as Ae. aegypti and Ae. albopictus ; increasing evidence suggests that vectorial competence can be modified by the microbiome (comprising both bacteriome and virome) of mosquitoes present in endemic zones. Using an RNA-seq-based metataxonomic approach, this study determined the virome structure of field-caught Ae. aegypti and Ae. albopictus mosquitoes in Medellín, Colombia, a municipality with a high incidence of mosquito-transmitted arboviruses. The two species are sympatric, but their core viromes differed considerably in richness, diversity, and abundance; the viromes were dominated by a few viruses. BLAST searches of assembled contigs suggested that at least 17 virus species (16 of which are insect-specific viruses [ISVs]) infect the Ae. aegypti population. Dengue virus 3 was detected in one sample. In Ae. albopictus , up to 11 ISVs and one plant virus were detected. Therefore, the virome composition was species-specific. The bacterial endosymbiont Wolbachia was identified in all Ae. albopictus samples and in some Ae. aegypti samples collected after 2017. The presence of Wolbachi a sp. in Ae. aegypti was not related to significant changes in the richness, diversity, or abundance of this mosquito’s virome, although it was related to an increase in the abundance of Aedes aegypti To virus 2 (unclassified). The mitochondrial diversity of these mosquitoes suggested that the Ae. aegypti population underwent a change that started in the second half of 2017, which coincides with the release of Wolbachia -infected mosquitoes in Medellín, indicating that the population of w Mel-infected mosquitoes has expanded. However, additional studies are required on the dispersal speed and intergenerational stability of w Mel in Medellín and nearby areas as well as on the introgression of genetic variants in the native mosquito population.

Momordica charantia L. extracts against Aedes aegypti larvae

Mormodica charantia (Curcubitaceae) is a plant with great medicinal potential, also used as an alternative of mosquitoes control as demonstrated by previous studies. We evaluated the larvicidal activity of crude extracts of ethyl acetate, methanol and hexane from flowers and fruits of M. charantia against Aedes aegypti (Culicidae). Flowers and fruits were macerated in methanol, ethyl acetate and hexane. Bioassays were performed with application of the extracts at final concentrations of 1 - 200 µg/mL in the middle of the third instar larvae of A. aegypti (L3). The results showed high toxicity to ethyl acetate extracts from flowers and fruits at concentrations of 200 µg/mL and 100 µg/mL, with 97% and 87% of larvae mortality (L3), respectively. Hexane extract demonstrated low toxicity, while methanol extract exhibited 78% larval mortality. The data suggested that the ethyl acetate extracts of flowers and fruits of M. charantia can effectively contribute to larvicidal activity. In addition, purification of M. charantia extracts may lead to a promising larvicidal activity to control the A. aegypti population.

Stability Analysis of a Mathematical Model for the Use of Wolbachia to Stop the Spread of Zika Virus Disease

Summary The use of wolbachia-infected mosquitoes to stop the spread of zika virus disease is modeled and analyzed. The model consists of a system of 10 ordinary differential equations which describes the dynamics of the disease in the human population, a wolbachia-free Aedes aegypti population, and a wolbachia-infected Aedes aegypti population used for disease control. A stability analysis of the disease-free equilibrium is conducted, which shows that it is both locally and globally asymptotically stable when the reproduction number is less than one. The result of the stability analysis shows that the spread of zika virus disease can be stopped, irrespective of the initial sizes of the infected human and mosquito populations, when wolbachia-infected Aedes aegypti are introduced in the area where the disease is endemic.

Status Resistensi Nyamuk Aedes aegypti dari Wilayah Kerja Puskesmas Salido terhadap Malathion 5% dan Alfa-sipermethrin 0,025%

Background: Insecticides resistance status in Aedes aegypti population is one of the factors that influence the successful control efforts of dengue vector. Objectives:To determine the resistance status of Aedes aegypti from Salido Health Center towards malathion 5% and alpha-cypermethrine 0,025%. Methods: This was a descriptive study and collected during December 2019 – June 2020. Those samples were then observed with larval survey and from the ovitrap placed in 100 houses and then maintained in laboratory of parasitology, faculty of medicine Andalas University. To determine the resistance status of Aedes aegyptiusing the bioassay method with the susceptibility test by referring to the guidance of the Ministry of Health based on the 2016 WHO standard using impregnated paper malathion 5% and alpha-sipermethrin 0.025%. Observations were made by recording the number of mosquito deaths in the 15, 30, 45, 60 and 1440 minutes. The percentage of mosquito deaths is calculated after 24 hours of maintenance it is categorized as resistant if the mortality rate is less than 90%, supected to be resistant if the mortality is between 90-97%, and categorized as vunerable if the mortality rate is between 98-100%.Result: The mortality rate of Aedes aegypti for 24 hours by malathion 5% was 95%, the LT50 and the LT90 were 624 minutes and 1.247 minutes respectively. The percentage of mosquito deaths by alpha-sipermetrin 0,025% after 24 hours was 96,25% the LT50 and the LT90 were 526 minutes and 1.163 minutes respectively.Conclusion: that the resistance status of Aedes aegypti from Salido Health Center is resistant towards malathion 5% and alpha-cypermethrine 0,025%.

Inhibition of defensin A and cecropin A responses to dengue virus 1 infection in Aedes aegypti

Introduction: It is essential to determine the interactions between viruses and mosquitoes to diminish dengue viral transmission. These interactions constitute a very complex system of highly regulated pathways known as the innate immune system of the mosquito, which produces antimicrobial peptides that act as effector molecules against bacterial and fungal infections. There is less information about such effects on virus infections.Objective: To determine the expression of two antimicrobial peptide genes, defensin A and cecropin A, in Aedes aegypti mosquitoes infected with DENV-1.Materials and methods: We used the F1 generation of mosquitoes orally infected with DENV-1 and real-time PCR analysis to determine whether the defensin A and cecropin A genes played a role in controlling DENV-1 replication in Ae. aegypti. As a reference, we conducted similar experiments with the bacteria Escherichia coli.Results: Basal levels of defensin A and cecropin A mRNA were expressed in uninfected mosquitoes at different times post-blood feeding. The infected mosquitoes experienced reduced expression of these mRNA by at least eightfold when compared to uninfected control mosquitoes at all times post-infection. In contrast with the behavior of DENV-1, results showed that bacterial infection produced up-regulation of defensin and cecropin genes; however, the induction of transcripts occurred at later times (15 days).Conclusion: DENV-1 virus inhibited the expression of defensin A and cecropin A genes in a wild Ae. aegypti population from Venezuela.

Novel Sterile Insect Technology (SIT) program results in suppression of a field mosquito population and subsequently to reduced incidence of dengue

Background There is a steady rise in the global incidence of Aedes-borne arbovirus disease. It has become urgent to develop alternative solutions for mosquito vector control. We developed a new method of sterilization of male mosquitoes, with the goal to suppress a local Aedes aegypti population and to prevent the spread of dengue. Methods Sterile male mosquitoes were produced from a locally acquired Ae. aegypti colony by using a treatment that includes double-stranded RNA and thiotepa. A field study was conducted, with sterile mosquito releases being performed on a weekly basis in predefined areas. Two intervention periods (INT1 and INT2) were carried out, with treatment and control areas reversed between INT1 and INT2. Results During INT1, releases in the treated area resulted in up to 91.4% reduction of live progeny of field Ae. aegypti mosquitoes recorded over time, while the control neighborhoods (no releases of sterile male mosquitoes) remained highly infested. The successful implementation of the program during INT1 and INT2 were associated with a 15.9-fold and 13.7-fold lower incidences of dengue in the treated area compared to the control areas, respectively. Conclusions Our data show the success of this new SIT-based program in preventing the spread of dengue.

Evidence of Metabolic Resistance in Pyrethroid Resistant Aedes aegypti Population from Lagos, Nigeria

Background: Pyrethroid resistance in Aedes aegypti is of major concern to the control of several arboviral infections. The major mechanisms of Pyrethroid resistance in mosquitoes are target-site insensitivity and elevation in the activity of detoxification enzymes. In this study, we assessed the susceptibility status of Aedes aegypti population from Lagos to Pyrethroid and the impact of metabolic enzymes on resistance development. Methods: Larvae of Aedes aegypti were collected from differ ent habitats in Lagos Mainland Local Government Area, Lagos state. Adult mosquitoes of 2-5 days were exposed to diagnostic dose of permethrin and Deltamethrin using the CDC method. Synergist assay was done with pre-exposure of samples to PBO before exposure to insecticide. Esterase and GST activities were measured using standard protocol. Regression Probit was used to compute the KDT50 and KDT95. Analysis of variance was used to compare the difference in mean of enzymes activities. Results: Aedes aegypti population from the study location is resistant to permethrin (33% ) and Deltamethrin (80%) within the diagnostic time. PBO pre-exposure increases percentage knockdown from 33% to 82% and 80% to 87% for permethrin and Deltamethrin respectively. The activity of GST was higher (P<0.05) in permethrin exposed mosquitoes in comparison with unexposed. Conclusion: A robust insecticide resistance management (IRM) plan in Lagos should take into consideration strategies for addressing the effects of metabolic enzymes in resistance development .