Biology subjects

Beebe, N. W.

Publications and source records attributed to Beebe, N. W..

3 recordsLinked to original sources

bioRxiv2024

Fitness compatibility and dengue virus inhibition in a Bangladeshi strain of Aedes aegypti infected with the Wolbachia strain wAlbB

Dengue cases in Bangladesh have surged in recent years. The existing insecticide-based control program, implemented in parts of the country, is challenged by issues of insufficient household coverage and high levels of insecticide resistance in the primary dengue virus (DENV) vector, Aedes aegypti. A more sustainable, effective alternative could be the implementation of a Wolbachia-mediated disease management strategy. Infecting mosquitoes with Wolbachia can change their reproductive compatibility and their ability to transmit DENV. These new phenotypes can be exploited to suppress or replace wild-type Ae. aegypti populations. Such strategies require the development of well-characterised Wolbachia-infected strains with biological characteristics that are comparable with local mosquitoes. We created and characterised a Wolbachia-infected Ae. aegypti strain with a Dhaka wild-type genetic background, and compared its reproductive compatibility, maternal inheritance, fitness, and virus-blocking ability to the parental strains (Dhaka wild-type and wAlbB2-F4). The new Ae. aegypti strain wAlbB2-Dhaka demonstrated complete cytoplasmic incompatibility with the wild-type strain and complete maternal transmission, retaining levels of pyrethroid resistance of the Dhaka wild-type (70% survival to 10 times the dose of permethrin expected to kill susceptible mosquitoes). No significant fitness costs were detected during laboratory comparisons of fecundity, fertility, survival, mating competitiveness, or desiccation tolerance. Compared to the wild-type strain, wAlbB2-Dhaka mosquitoes had a significantly reduced number of DENV genome copies in the bodies (44.4%, p = 0.0034); two-fold reduction in dissemination to legs and wings (47.6%, p < 0.0001); and >13-fold reduction of DENV in saliva expectorates (proxy of transmission potential) (92.7%, p < 0.0001) 14 days after ingesting dengue-infected blood. Our work indicates that the wAlbB2-Dhaka strain could be used for Ae. aegypti suppression or replacement strategies for dengue management in Bangladesh. Author summaryBangladesh is currently grappling with a series of severe dengue outbreaks, resulting in more than 300 thousand infections, 1700 fatalities, and a significant influx of patients requiring hospitalisation in 2023. These outbreaks coincide with the emergence of high levels of insecticide resistance in the Ae. aegypti population, which is contributing to the failure of conventional, insecticidal control strategies. In search of more sustainable, effective dengue control strategies, approaches using the endosymbiotic bacteria Wolbachia that render mosquitoes resistant to arbovirus infection are being trialled in a number of countries. We transinfected Dhaka wild-type Ae. aegypti with the Wolbachia strain wAlbB2 by backcrossing it with a Wolbachia wAlbB2-infected Ae. aegypti strain and assessed the new strains suitability for field release. We compared the fitness and virus-blocking ability of the backcrossed strain with its parental strains. We demonstrated that the new strain, wAlbB2-Dhaka, is as fit as the Dhaka wild-type strain and blocked [~]92% of dengue virus transmission. This strain has great potential for Wolbachia-mediated dengue management strategies in Bangladesh.

zoology↗

bioRxiv2022

Wolbachia wAlbB inhibit dengue and Zika infection in the mosquito Aedes aegypti with an Australian background

Biological control of mosquito vectors using the insect-specific bacteria Wolbachia is an emerging strategy for the management of human arboviral diseases. We recently described the development of a strain of Ae. aegypti infected with the Wolbachia strain wAlbB (referred to as the wAlbB2-F4 strain) through simple backcrossing of wild type Australian mosquitoes with a wAlbB infected Ae. aegypti strain from the USA. Field releases of male wAlbB2-F4 mosquitoes resulted in the successful suppression of a wild population of mosquitoes in the trial sites by exploiting the strains Wolbachia-induced cytoplasmic incompatibility. We now demonstrate that the strain is resistant to infection by dengue and Zika viruses and is genetically similar to endemic Queensland populations. There was a fourfold reduction in the proportion of wAlbB2-F4 mosquitoes that became infected following a blood meal containing dengue 2 virus (16.7%) compared to wild type mosquitoes (69.2%) and a 6-7 fold reduction in the proportion of wAlbB2-F4 mosquitoes producing virus in saliva following a blood meal containing an epidemic strain of Zika virus (8.7% in comparison to 58.3% in wild type mosquitoes). Restriction-site Associated DNA (RAD) sequencing revealed that wAlbB2-F4 mosquitoes have > 98% Australian ancestry, confirming the successful introduction of the wAlbB2 infection into the Australian genomic background through backcrossing. Genotypic and phenotypic analyses showed the wAlbB2-F4 strain retains the insecticide susceptibility phenotype and genotype of the Australian mosquitoes. We demonstrate that the Wolbachia wAlbB2-F4, in addition to being suitable for suppression programs, can be effective in population replacement programs given its high inhibition of virus infection in mosquitoes. The ease at which a target mosquito population can be transfected with wAlbB2, while retaining genotypes and phenotypes of the target population, shows the robustness of this strain as a biocontrol agent against the Ae. aegypti mosquito itself as well as the pathogens it transmits. IMPORTANCEEpidemics of arthopod-borne virus (arbovirus) diseases affect millions of people and are becoming more frequent and widespread. A successful strategy to control these diseases is by infecting mosquito populations with benign, insect-specific Wolbachia bacteria that render mosquitoes refractory to infection with pathogenic arboviruses. Here we show that a strain of the major mosquito vector Ae. aegypti that was infected with Wolbachia following a simple back-cross mating procedure is refractory to infection with dengue and Zika viruses. Importantly, the genetic background of the strain is equivalent to the target population, which is important for persistence of the strain and regulatory approval.

microbiology↗

bioRxiv2020

Mark-release-recapture of male Aedes aegypti (Diptera: Culicidae): use of rhodamine B to estimate movement, mating and population parameters in preparation for an incompatible male program.

Rapid advances in biological and digital technologies are revolutionizing the population control of invasive disease vectors such as Aedes aegypti. Methods such as the sterile and incompatible insect techniques (SIT/IIT) rely on modified males to seek out and successfully mate with females, and in doing so outcompete the wild male population for mates. Currently, these interventions infer the success of mating interactions between male and female insects through area-wide population surveillance and observations of mating competitiveness are rare. Furthermore, little is known about male Ae. aegypti behaviours and biology in field settings. In preparation for a large, community scale IIT program, we undertook a series of mark-release-recapture experiments using rhodamine B to mark male Ae. aegypti sperm and measure mating interactions with females. We also developed the Spatial and Temporally Evolving Isotropic Kernel (STEIK) framework to assist researchers to estimate the movement of individuals through space and time. Results showed that ~40% of daily females captured were unmated, suggesting interventions will need to release males regularly to be effective at suppressing Ae. aegypti populations. Males moved rapidly through the landscape, particularly when released during the night. Although males moved further than what is typically observed in females of the species, survival was considerably lower. These unique insights will lead to a greater understanding of mating interactions in wild insect populations and lay the foundation for robust suppression strategies in the future. Author SummaryModern scientific techniques for controlling populations of the dengue vector, Aedes aegypti, utilize the mating biology of adult male mosquitoes to achieve suppression through a sterilization process. As the study of Ae. aegypti control has typically focused on adult female mosquitoes, knowledge on male movement, survival and mating interactions in the field is lacking. Here we undertook several mark-release-recapture experiments on adult male Ae. aegypti in Innisfail, Australia, and measured important biological parameters. For the first time in large field experiments, we employed rhodamine B as a marker that when fed to adult males, identified both marked males and the wild females they mated with. We observed males moving further through the landscape, but surviving for a shorter period, than previous measurements undertaken on females in a field setting. A high proportion (~40%) of unmated females suggests individuals are constantly available for mating. As such, sterile male strategies may need to release at regular intervals to achieve effective population suppression. The unique insights provided by this study will assist in designing future sterile male field interventions.

ecology↗