The research focused on the yellow fever mosquito Aedes aegypti, the Asian tiger mosquito Aedes albopictus, and the house mosquito Culex pipiens, three species that together transmit dengue, Zika, chikungunya, yellow fever, West Nile virus, and lymphatic filariasis. Decades of reliance on a small arsenal of synthetic insecticides, including organophosphates and pyrethroids, has driven the evolution of resistant mosquito populations on multiple continents, prompting public health agencies to call for novel modes of action. Boron chemistry, until now largely absent from the vector-control literature, offers a genuinely fresh starting point.

Boron-based compounds have attracted growing attention in medicinal chemistry because of their antimicrobial, cytotoxic, and broadly bioactive properties. Naturally occurring boron macrolides such as aplasmomycin and boromycin demonstrated antibiotic and even anti-HIV activity, while synthetic boron clusters and boronate esters have found roles in drug design, diagnostics, and therapy. Yet the insecticidal potential of one particular structural class, the 1,2-diborane derivatives, had never been systematically tested against mosquito larvae. The new study set out to fill that gap, combining synthetic chemistry, crystallography, toxicology, and histopathology in a single investigation.

The team, led by Yüksel Şahin of Aydın Adnan Menderes University together with Fatma Bursalı, Yücel Basimoglu Koca, Muhittin Aygün, Hakan Can Söyleyici, Resul Sevincek, and Hüseyin Özgener, worked with five previously synthesized diborane and diborolane derivatives and added a brand-new molecule to the collection. This sixth compound, a 1,3,2-diazaborinane derivative designated compound 6, was synthesized and fully characterized, with its three-dimensional structure confirmed by single-crystal X-ray diffraction. The crystallographic data, deposited with the Cambridge Crystallographic Data Centre under accession number 2414655, allowed the researchers to relate the precise arrangement of substituents around the boron atoms to biological performance, a classic structure–activity analysis.

When the six compounds were tested against late third- and fourth-instar larvae of all three mosquito species, the results were strikingly consistent. Every compound displayed significant larvicidal activity. Probit analysis, a statistical method for quantifying dose–response relationships, yielded lethal concentration fifty values ranging from 16.712 to 30.087 micrograms per milliliter for Aedes aegypti, from 17.417 to 32.636 micrograms per milliliter for Aedes albopictus, and from 17.789 to 28.582 micrograms per milliliter for Culex pipiens. In practical terms, the most potent molecules killed half of the exposed larvae at concentrations in the tens of micrograms per milliliter range, a level of activity that places them firmly on the radar as candidate larvicides.

Not all of the molecules performed equally, however, and the differences proved chemically informative. Compounds 1 and 2 emerged as the most potent larvicides across all three species, while compounds 3, 4, and the newly synthesized diazaborinane compound 6 were comparatively less active. The authors attribute this gradient to the nature of the substituents attached to the boron atoms, suggesting that strongly donating groups on boron enhance biological activity. This kind of structure–activity relationship is the raw material of drug and pesticide discovery: it tells synthetic chemists which molecular features to keep and which to modify as they optimize potency, stability, and selectivity in future generations of compounds.

To understand how the compounds kill, the researchers turned to histopathology, examining stained tissue sections of larvae that had been exposed to the molecules and comparing them with untreated controls. The picture that emerged was unambiguous: the primary targets are the gastric caeca and the midgut epithelium, the tissues responsible for digestion and nutrient absorption in the larval gut. Exposed larvae showed epithelial disruption, cytoplasmic vacuolization, cellular swelling, degeneration of the microvilli that line the gut surface, and damage to the peritrophic membrane, the protective chitinous sleeve that shields the midgut from mechanical and chemical insult.

These lesions matter physiologically. The peritrophic matrix is a critical barrier in insect digestion and a first line of defense against pathogens and toxins, and its disruption exposes the underlying epithelium to direct chemical attack. Vacuolization and swelling of epithelial cells are hallmarks of cellular stress and impending cell death, while the loss of microvilli drastically reduces the absorptive surface of the gut. A larva whose midgut is compromised in this way effectively starves and loses fluid balance, a mode of action that is distinct from the neurotoxic mechanisms of pyrethroids and organophosphates, which is precisely what makes the finding valuable for resistance management.

Intriguingly, the severity of tissue injury varied among the three mosquito species. Aedes aegypti, the primary vector of dengue and yellow fever, suffered the most severe alterations, Culex pipiens showed moderate damage, and Aedes albopictus displayed relatively mild changes. This species-specific pattern of susceptibility hints at differences in gut physiology, cuticular penetration, or detoxification enzyme activity among the three vectors, and it underscores the need to evaluate any new larvicide against the full range of target species rather than extrapolating from a single laboratory model.

The authors are careful to frame the work as a foundation rather than a finished product. Their conclusion emphasizes that diborane derivatives, particularly those bearing specific substituents on the boron atoms, exhibit significant biological activity against mosquito larvae with toxic effects concentrated on the larval digestive system, and that the results support further investigation of these compounds as potential larvicidal candidates. At the same time, they stress that studies on selectivity toward non-target organisms, and on mechanisms of action under both laboratory and field-relevant conditions, are required before any practical application can be contemplated. The gap between a promising laboratory LC50 value and a deployable vector-control product is wide, encompassing environmental fate, effects on aquatic ecosystems, formulation, cost, and regulatory approval.

Even so, the study arrives at a moment of genuine urgency. Dengue incidence has surged globally, vaccine development has been slow and uneven, and the World Health Organization’s Global Vector Control Response 2017–2030 explicitly calls for new tools and new chemistries. Resistance to bacterial larvicidal toxins and to synthetic insecticides continues to erode the effectiveness of existing programs, and climate change is expanding the geographic range of Aedes and Culex vectors into temperate regions. Against that backdrop, a chemically novel class of compounds with a gut-targeted mode of action and clear structure–activity guidance for optimization represents exactly the kind of lead that vector biologists have been asking for. The next steps, testing non-target organisms such as aquatic invertebrates and fish, probing the molecular mechanism of boron toxicity in insect cells, and validating efficacy in semi-field and field trials, will determine whether these unusual molecules can graduate from the crystallography bench to the mosquito-control toolkit. For now, the humble boron atom, better known for its role in plant cell walls and cancer therapy, has earned a place in the conversation about the future of mosquito control.

Subject of Research: Larvicidal activity and histopathological effects of diborane derivatives against Aedes and Culex mosquito larvae

Article Title: Synthesis, Structure–Activity Considerations and Histopathological Effects of Diborane Derivatives as Mosquito Larvicides

Article References: Şahin, Y., Bursali, F., Koca, Y. B., Aygün, M., Söyleyici, H. C., Sevincek, R., & Özgener, H. (2026). Synthesis, Structure–Activity Considerations and Histopathological Effects of Diborane Derivatives as Mosquito Larvicides. Acta Parasitologica, 71(5), Article 221. https://doi.org/10.1007/s11686-026-01390-2

Image Credits: AI Generated

DOI: 10.1007/s11686-026-01390-2

Keywords: diborane derivatives, mosquito larvicides, Aedes aegypti, Aedes albopictus, Culex pipiens, boron chemistry, histopathology, midgut epithelium, structure–activity relationship, vector control, insecticide resistance, diazaborinane

The study, published in Virology Journal, focused on Culex pipiens sensu lato and Culiseta annulata, two species that dominate the UK mosquito fauna and are considered among the most plausible vectors should arboviruses such as West Nile or Usutu virus establish local transmission cycles. Between 2021 and 2022, the team collected adult mosquitoes across the grounds of the two zoological collections, sites chosen deliberately because zoos concentrate large numbers of animals in outdoor enclosures where mosquitoes feed readily. That combination of abundant vectors, diverse vertebrate hosts and regular human visitors makes zoological collections potential interfaces for virus exchange between mosquitoes, animals and people, and therefore valuable sentinel locations for surveillance.

In total, 4,042 mosquitoes were processed and sequenced across 44 pools. The researchers extracted total nucleic acids and applied a metagenomic sequencing strategy designed to capture both RNA and DNA viruses, allowing them to recover viral genomes without relying on prior assumptions about which viruses might be present. Bioinformatic assembly and taxonomic classification of the resulting reads yielded 26 viral genomes, a striking haul for a country whose mosquito viromes have remained comparatively understudied. Nine of these represented entirely novel species, distributed across both RNA and DNA virus families, underscoring how much basic viral diversity in northern European mosquitoes still awaits description.

A consistent pattern emerged across the sampling sites: several viruses were detected in every pool analysed, indicating substantial overlap in virome composition between the two zoos. This shared core of viruses suggests that certain mosquito-associated viruses are widespread and stable components of the local mosquito fauna rather than isolated curiosities confined to a single habitat. Such ubiquity matters for risk assessment, because a virus that maintains itself efficiently across geographically separated mosquito populations has, by definition, the ecological flexibility that emergence requires, even if most of these viruses ultimately prove harmless to vertebrates.

The headline findings are two novel orthobunyaviruses, named Atherstone virus and Deva virus, belonging to the family Peribunyaviridae. Orthobunyaviruses are a genus with a serious pedigree: it includes recognised human and animal pathogens such as Schmallenberg virus, which devastated European ruminant farming after its emergence in 2011, and Oropouche virus, a growing public health concern in the Americas. The tripartite RNA genomes of orthobunyaviruses encode a viral RNA-dependent RNA polymerase on the large segment, surface glycoproteins on the medium segment, and nucleoprotein plus accessory proteins on the small segment. Finding two previously unknown members of this genus in British mosquitoes immediately elevates them to candidates for closer scrutiny.

Not all orthobunyaviruses pose equal risk, and the study went beyond simple detection to ask which of the two new viruses resembles a genuine arbovirus, capable of replicating in both mosquitoes and vertebrate hosts. The team employed MosViR, a machine-learning classification tool trained on known mosquito viruses to predict whether a given virus is likely to be mosquito-restricted or arthropod-borne. For Atherstone virus, detected at both zoos, the prediction pointed towards arbovirus status, a result that alone would justify follow-up. More compelling still was the genomic evidence: Atherstone virus carries an open reading frame encoding a non-structural protein S, or NSs, a well-characterised virulence factor in orthobunyaviruses that antagonises host antiviral responses, including the interferon system, and is a hallmark of pathogenic members of the genus.

Deva virus tells a different story. Its small segment lacks an NSs open reading frame altogether, and MosViR did not predict it to be an arbovirus. The absence of NSs, combined with the absence of a vertebrate-infecting signature, is consistent with Deva virus being an insect-specific virus, locked into replication within mosquito cells and their close relatives. Insect-specific viruses of this kind are increasingly recognised as common and sometimes abundant residents of mosquito viromes. Although they do not infect vertebrates directly, they are far from biologically irrelevant: they can modulate mosquito immunity, compete with arboviruses for cellular resources, and in some cases reduce the ability of mosquitoes to transmit pathogenic viruses, making them subjects of interest both for basic virology and for potential interference-based control strategies.

The broader viral inventory recovered in the study reinforces this picture of a layered virome. Alongside the orthobunyaviruses, the sequencing identified viruses spanning multiple families, including flavivirus-like and other RNA virus groups as well as DNA viruses, with several classified as novel species. Distinguishing arboviruses from insect-specific viruses is one of the central analytical challenges in mosquito metagenomics, because both can be present in the same sample and their genomes can be difficult to interpret from sequence data alone. Tools such as MosViR, combined with comparative genomics against reference databases and catalogues of known arboviruses, provide a probabilistic framework for triage, flagging which discoveries warrant experimental characterisation in cell culture and vertebrate systems and which can be provisionally set aside as likely insect-restricted.

Why does this matter for the United Kingdom specifically? The country sits at the northern edge of the range of many mosquito species, and climate warming, changes in land use and the movement of animals and goods are all expected to alter the dynamics of mosquito-borne disease in temperate Europe. Usutu virus has already established itself in British birds and mosquitoes, and West Nile virus circulates periodically in neighbouring countries. Risk frameworks built around these known threats are essential, but the new study argues that they should be complemented by surveillance for the unknown: viruses already resident in local vectors whose properties have never been tested. A virus that today appears to be insect-specific could, through reassortment with a related pathogen or through evolutionary change, acquire new capabilities. Orthobunyaviruses are particularly notable in this respect because their segmented genomes can reassort when mosquitoes are co-infected with related viruses, generating novel combinations with unpredictable host ranges.

The authors are careful not to overstate the immediate danger. Detection of a viral genome in a mosquito does not demonstrate that the virus infects or harms vertebrates, and neither Atherstone nor Deva virus has been shown to cause disease. What the study provides is a prioritised list of candidates and a demonstration of method: that large-scale metagenomic surveillance of UK mosquitoes is feasible, productive and capable of revealing both the diversity of local viromes and the specific viruses that merit laboratory follow-up. Isolation of Atherstone virus, characterisation of its host range, and serological surveys of animals and humans near the sampling sites would be the logical next steps. In the meantime, the work adds the United Kingdom to the growing map of regions where the viruses closest to home, rather than those arriving from abroad, are proving to be the first order of business for emerging infection surveillance.

Subject of Research: Metagenomic surveillance of mosquito viromes at two UK zoos reveals novel mosquito-associated orthobunyaviruses

Article Title: Emergence risks from within? Metagenomic analysis of mosquito viromes from two zoos reveals mosquito-associated orthobunyaviruses in the UK

Article References: Pilgrim, J., Seechurn, N., Cunningham-Oakes, E., Gillespie, L., Dobbs, P., Lopez, J., Kohl, A., Hughes, G. L., Blagrove, M. S. C., Baylis, M., & Darby, A. C. (2026). Emergence risks from within? Metagenomic analysis of mosquito viromes from two zoos reveals mosquito-associated orthobunyaviruses in the UK. Virology Journal. https://doi.org/10.1186/s12985-026-03305-z

Image Credits: AI Generated

DOI: 10.1186/s12985-026-03305-z

Keywords: orthobunyavirus, mosquito, virome, metagenomics, arbovirus, Culex pipiens, Culiseta annulata, surveillance, zoonotic risk, insect-specific virus, United Kingdom, Peribunyaviridae

The research, led by Kylee R. Noel and colleagues at the University of Illinois Urbana-Champaign and the Illinois Natural History Survey, set out to answer a question that has received surprisingly little rigorous experimental attention. Insecticides applied to agricultural fields, suburban lawns, and mosquito control zones inevitably find their way into surface waters, where concentrations rarely reach levels that kill mosquito larvae outright. Yet these sublethal concentrations can still perturb larval physiology, development, and behavior. Because many of the traits that determine how efficiently a mosquito transmits a virus — adult survival, fecundity, and vector competence — are shaped during the aquatic juvenile stages, the researchers hypothesized that early-life insecticide exposure could leave a lasting imprint on transmission potential.

To test this, the team reared Culex pipiens larvae under standard insectary conditions, with temperatures maintained at approximately 27.6 degrees Celsius, relative humidity around 70 percent, and a photoperiod of 16 hours of light and 8 hours of darkness. One group of larvae was exposed to a sublethal concentration of permethrin, a widely used synthetic pyrethroid insecticide, at 0.01 milligrams per liter — a dose low enough not to cause mortality but high enough to exert physiological stress. Upon eclosion, adult mosquitoes from both the exposed and unexposed control groups were transferred into environmental chambers held at either 25 or 29 degrees Celsius, two temperatures within the range that Culex pipiens routinely experiences during the summer transmission season in the American Midwest.

The experimental design is notable because it separates the larval and adult environments, allowing the investigators to disentangle effects that occur during development from those imposed on the adult stage. Mosquitoes infected with West Nile virus were then monitored across the key parameters that together constitute vectorial capacity, the epidemiological framework used to estimate how effectively a vector population can transmit a pathogen. These parameters include adult survival, which determines how long a female lives and therefore how many blood meals she can take; fecundity, which influences population growth; and vector competence, a composite measure encompassing infection rate, dissemination rate from the midgut to other tissues, and the ability to transmit virus in saliva during a subsequent bite.

The life-history results revealed that permethrin exposure during the larval stage slowed development: exposed larvae took longer to mature into adults than untreated controls. More strikingly, the adult females that emerged from treated larvae survived longer than their control counterparts. Extended adult longevity is a critical variable in vectorial capacity, because the extrinsic incubation period of West Nile virus — the time it takes for an infected mosquito to become infectious — must be shorter than the mosquito’s lifespan for transmission to occur. Females that live longer have a greater probability of surviving that incubation window and biting another host while infectious, effectively multiplying their contribution to the transmission cycle.

Temperature exerted its own powerful influence on the virological side of the equation. At 29 degrees Celsius, mosquitoes showed higher infection and dissemination rates, and viral RNA was detected at greater levels within mosquito tissues, compared with the cooler 25 degree environment. This pattern is consistent with a broader literature showing that warmer temperatures accelerate viral replication within mosquito vectors, shortening the extrinsic incubation period and pushing mosquitoes to infectious status sooner after an infective blood meal. However, the study’s most consequential finding emerged when the two stressors were analyzed together rather than in isolation.

At 29 degrees Celsius, the control mosquitoes — those with no larval insecticide exposure — exhibited the lowest transmission potential of any group in the experiment. By contrast, mosquitoes that had been exposed to permethrin as larvae displayed markedly higher transmission potential under the same warm conditions. This interaction indicates that sublethal pesticide exposure and elevated temperature do not simply add their effects; they combine in a non-additive manner that reshapes the overall transmission equation. A warmer world, in other words, may not uniformly increase West Nile virus risk — the outcome depends on what the vector population experienced during its aquatic development, and urban or agricultural waters contaminated with pyrethroid residues could tip the balance toward greater transmission.

Why would larval chemical stress enhance transmission potential at high temperatures while control mosquitoes fared worse? The authors’ data suggest that the combination of extended adult survival in permethrin-exposed females and temperature-driven gains in infection and dissemination rates produced a population of longer-lived, more competent vectors precisely under the conditions where unexposed mosquitoes performed least well. The physiological mechanisms linking larval permethrin exposure to adult longevity and vector competence were not fully resolved in this experiment, but stress-induced changes in larval metabolism, immune priming, or resource allocation could plausibly alter adult physiology in ways that interact with viral kinetics at elevated temperatures. Further mechanistic work will be needed to pin down these pathways, and the authors note that their experiment used a single permethrin concentration and two adult temperatures, leaving open questions about dose-response relationships and the full thermal range experienced in the field.

The public health and environmental implications are substantial. Mosquito abatement districts routinely apply pyrethroids as larvicides and adulticides, and agricultural runoff delivers additional residues into stormwater ponds, drainage ditches, and other habitats where Culex pipiens breeds. If those residues leave surviving larvae physiologically primed for greater transmission as adults — particularly during heat waves, when West Nile virus epidemics historically peak — then conventional insecticide use could carry an unrecognized trade-off: suppressing mosquito abundance in the short term while inadvertently enhancing the transmission efficiency of the mosquitoes that survive. The study therefore argues for integrated surveillance that monitors not just mosquito numbers but the chemical and thermal conditions of larval habitats, especially in environments exposed to rising temperatures driven by climate change.

As with all laboratory studies, translating these results to real-world epidemics will require field validation, since wild mosquito populations encounter fluctuating temperatures, heterogeneous insecticide mixtures, and competing larval stresses that a controlled chamber experiment cannot fully replicate. Nevertheless, the work provides a clear experimental demonstration that the developmental environment of a disease vector can rewrite the rules of transmission established by adult conditions alone. For a virus like West Nile, whose seasonal dynamics depend on a delicate interplay between vectors, hosts, and climate, understanding these cross-generational and cross-stressor interactions may prove essential for predicting and preventing the outbreaks of the future. The research was supported by the State of Illinois Used Tire Management and Emergency Public Health funds and by a grant from the University of Illinois Center for Advanced Climate Solutions.

Subject of Research: Interaction of sublethal insecticide exposure and temperature on West Nile virus transmission by Culex pipiens mosquitoes

Article Title: Sublethal insecticide exposure and temperature interact to shape West Nile virus transmission potential of Culex pipiens

Article References: Sublethal insecticide exposure and temperature interact to shape West Nile virus transmission potential of Culex pipiens. (n.d.). https://doi.org/10.1186/s13071-026-07700-x

Image Credits: AI Generated

DOI: 10.1186/s13071-026-07700-x

Keywords: West Nile virus, Culex pipiens, permethrin, sublethal exposure, vector competence, vectorial capacity, temperature, insecticide pollution, mosquito-borne disease, Parasites & Vectors, life history traits, climate change