Does arbovirus emergence in humans require adaptation to domestic mosquitoes?

Genomics of urban adaptation and exaptation in mosquitoes and consequences for vectorial capacity

As urbanization accelerates around the world, mosquitoes that are capable of surviving and thriving in urban habitats increasingly spread mosquito-borne diseases. Across the >3,500 known species of mosquitoes, only a few rapidly adapted to the novel (on an evolutionary timescale) urban environments. In this review we highlight several emerging themes and testable hypotheses from recent literature. First, apparent urban adaptations can be roughly divided into newer adaptations arising in an urban context and exaptations - traits that evolved in a different context, prior to modern urbanization. Second, variants involved in urban adaptation are often partitioned among species complexes and cryptic lineages, and the history of gene flow-selection balance may be related to the evolution of compact genomic architectures that could facilitate rapid urban adaptation. Third, urban adaptation often has consequences for vectorial capacity - the ability of mosquitoes to serve as effective vectors of a particular pathogen - though the selective drivers and genetic mechanisms underlying these differences are incompletely understood. To fully understand urban adaptation in mosquitoes, we advocate for a coordinated effort to increase linkages between evolutionary ecology, population genomics, and medical entomology research. We discuss the two traits for which all three perspectives are the most developed - host preference and insecticide resistance - before reviewing several other less studied traits.

Development of Attractive Toxic Sugar Baits (ATSBs) System and Its Effectiveness in Mosquito Control

BACKGROUND

Attractive Toxic Sugar Baits (ATSBs) are an innovative vector control strategy based on the "attract-and-kill" principle. The core of ATSBs lies in the preparation of attractive and toxic baits through the mixing and proportioning of luring and active ingredients. Although previous studies have investigated the effects of ATSBs on mosquitoes, significant challenges remain for broader field application.

METHODS

This study evaluated five fruit juices as ATSBs for mosquitoes, focusing on feeding preferences. Preservative concentrations were assessed by measuring antimicrobial activity over time. Two commercial traps were tested for mosquito entry rates. The optimal insecticide species and concentration were determined based on mortality rates. An optimized ATSBs system was developed and tested under a semi-field cage. Statistical analysis was performed using GraphPad Prism.

RESULTS

Within 24 h, apple juice-based ATSBs had the highest attractant index for Culex quinquefasciatus and Anopheles sinensis, while a pear juice-based ATSB was most effective for Aedes albopictus. A 0.1% preservative concentration best maintained juice stability. The LC50 values of dinotefuran-based ATSBs for Cx. quinquefasciatus, Ae. albopictus, and An. sinensis were 1.18 × 10-3, 4.06 × 10-4, and 5.20 × 10-5 g/L, respectively. The Spodoptera frugiperda trap outperformed the Drosophilidae trap. Simulated semi-field cage tests showed 48 h mortality rates of 86.00% for Cx. quinquefasciatus and 95.67% for Ae. albopictus.

CONCLUSION

This study optimized an ATSB system by screening various fruit juices, preservative concentrations, insecticides, and trap devices. The system's efficacy in mosquito control was evaluated under a semi-field cage. These findings provide a strong foundation for the future application and refinement of ATSB-based mosquito control strategies.

Polygenic viral factors enable efficient mosquito-borne transmission of African Zika virus

Zika virus (ZIKV) is a mosquito-borne flavivirus primarily transmitted among humans by Aedes aegypti. Over the past two decades, it has caused significant outbreaks associated with birth defects and neurological disorders. Phylogenetically, ZIKV consists of two main genotypes referred to as the African and Asian lineages, each exhibiting distinct biological properties. African lineage strains are transmitted more efficiently by mosquitoes, but pinpointing the genetic basis of this difference has remained challenging. Here, we address this question by comparing recent African and Asian strains using chimeric viruses, in which segments of the parental genomes are swapped. Our results show that the structural genes from the African strain enhance viral internalization, while the non-structural genes improve genome replication and infectious particle production in mosquito cells. In vivo mosquito transmission is most significantly influenced by the structural genes, although no single viral gene alone determines this effect. Additionally, we develop a stochastic model of in vivo viral dynamics in mosquitoes that mirrors the observed patterns, suggesting that the primary difference between the African and Asian strains lies in their ability to traverse the mosquito salivary glands. Overall, our findings suggest that the polygenic nature of ZIKV transmissibility has prevented Asian lineage strains from achieving the same epidemic potential as African lineage strains, underscoring the importance of lineage-specific adaptive landscapes in shaping ZIKV evolution and emergence.

Translating mosquito viromes into vector management strategies

Mosquitoes are best known for transmitting human and animal viruses. However, they also harbour mosquito-specific viruses (MSVs) as part of their microbiota. These are a group of viruses whose diversity and prevalence overshadow their medically relevant counterparts. Although metagenomics sequencing has remarkably accelerated the discovery of these viruses, what we know about them is often limited to sequence information, leaving much of their fundamental biology to be explored. Understanding the biology and ecology of MSVs can enlighten our knowledge of virus-virus interactions and lead to new innovations in the management of mosquito-borne viral diseases. We retrace the history of their discovery and discuss research milestones that would line the path from mosquito virome knowledge to vector management strategies.

Intrinsic factors driving mosquito vector competence and viral evolution: a review

Mosquitoes are responsible for the transmission of numerous viruses of global health significance. The term "vector competence" describes the intrinsic ability of an arthropod vector to transmit an infectious agent. Prior to transmission, the mosquito itself presents a complex and hostile environment through which a virus must transit to ensure propagation and transmission to the next host. Viruses imbibed in an infectious blood meal must pass in and out of the mosquito midgut, traffic through the body cavity or hemocoel, invade the salivary glands, and be expelled with the saliva when the vector takes a subsequent blood meal. Viruses encounter physical, cellular, microbial, and immunological barriers, which are influenced by the genetic background of the mosquito vector as well as environmental conditions. Collectively, these factors place significant selective pressure on the virus that impact its evolution and transmission. Here, we provide an overview of the current state of the field in understanding the mosquito-specific factors that underpin vector competence and how each of these mechanisms may influence virus evolution.