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Pandemics originating from zoonotic viruses have posed significant threats to human health and agriculture. Recent discoveries have revealed that wild-rice plants also harbour viral pathogens capable of severely impacting rice production, a cornerstone food crop. In this study, we conducted virome analysis on ~1000 wild-rice individual colonies and discovered a novel single-strand positive-sense RNA virus prevalent in these plants. Through comprehensive genomic characterization and comparative sequence analysis, this virus was classified as a new species in the genus Polerovirus, designated Rice less tiller virus (RLTV). Our investigations elucidated that RLTV could be transmitted from wild rice to cultivated rice via a specific insect vector, the aphid Rhopalosiphum padi, causing less tiller disease symptoms in rice plants. We generated an infectious cDNA clone for RLTV and demonstrated systemic infection of rice cultivars and induction of severe disease symptoms following mechanical inoculation or stable genetic transformation. We further illustrated transmission of RLTV from stable transgenic lines to healthy rice plants by the aphid vector, leading to the development of disease symptoms. Notably, our database searches showed that RLTV and another polerovirus isolated from a wild plant species are widely circulating not only in wild rice but also cultivated rice around the world. Our findings provide strong evidence for a wild plant origin for rice viruses and underscore the imminent threat posed by aphid-transmitted rice Polerovirus to rice cultivar., (© 2024 John Wiley & Sons Ltd.)

Diaphorina citri transmits Candidatus Liberibacter asiaticus (CLas) between citrus plants which causes the expression of huanglongbing disease in citrus. D. citri flavi-like virus (DcFLV) co-occurs intracellularly with CLas in D. citri populations in the field. However, the impact(s) of DcFLV presence on the insect vector and its interaction with the CLas phytopathogen remain unclear. We compared CLas acquisition and transmission efficiencies as well as transcriptomic expression between viruliferous and non-viruliferous psyllids at multiple life stages. Viruliferous nymphs acquired higher titers of CLas than non-viruliferous nymphs, whereas viruliferous adults acquired less CLas than those without virus. The presence of DcFLV increased the transmission of CLas by both nymphs and adults. Furthermore, RNA-seq and functional gene expression analyses revealed that endoplasmic reticulum stress-, autophagy-, and defense-related genes were significantly upregulated in viruliferous adult psyllids, whereas most of these genes were downregulated in viruliferous nymphs. Our work demonstrates that DcFLV differentially modulates various cellular and physiological functions in D. citri in a life stage-dependent manner and promotes the acquisition of CLas at the nymphal stage and transmission of the pathogen at the adult stage of the vector. Collectively, our results suggest that D. citri vectors with DcFLV exhibit greater pathogen transmission efficiency than those without virus., Importance: Huanglongbing (HLB), caused by fastidious bacteria from three Candidatus Liberibacter species, is the most damaging disease impacting the citrus industry worldwide. Spread by the Asian citrus psyllid ( Diaphorina citri ) in Asia and the Americas, HLB causes substantial financial losses, and has reduced citrus production in Florida by more than 90%. Although there are ongoing efforts to limit spread of the disease, effective HLB management remains elusive. Suppressing vector populations and decreasing CLas transmission are the two strategies that need to be urgently improved. Recently, a D. citri flavi-like virus (DcFLV) was characterized within its D. citri host, and it co-occurs intracellularly with CLas in psyllid populations. Here, we show that viruliferous nymphs exhibit higher CLas acquisition than non-viruliferous nymphs. Furthermore, both viruliferous adults and nymphs exhibit increased CLas transmission efficiency. We suggest the possibility of manipulating DcFLV in D. citri populations to reduce CLas transmission for HLB disease management., Competing Interests: The authors declare no conflict of interest.

Background: Virus infection and herbivory can alter the expression of stress-responsive genes in plants. This study employed high-throughput transcriptomic and alternative splicing analysis to understand the separate and combined impacts on host gene expression in Arabidopsis thaliana by Myzus persicae (green peach aphid), and turnip mosaic virus (TuMV)., Results: By investigating changes in transcript abundance, the data shows that aphids feeding on virus infected plants intensify the number of differentially expressed stress responsive genes compared to challenge by individual stressors. This study presents evidence that the combination of virus-vector-host interactions induces significant changes in hormone and secondary metabolite biosynthesis, as well as downstream factors involved in feedback loops within hormone signaling pathways. This study also shows that gene expressions are regulated through alternative pre-mRNA splicing and the use of alternative transcription start and termination sites., Conclusions: These combined data suggest that complex genetic changes occur as plants adapt to the combined challenges posed by aphids and the viruses they vector. This study also provides more advanced analyses that could be used in the future to dissect the genetic mechanisms mediating tripartite interactions and inform future breeding programs., Competing Interests: Declarations. Ethics approval and consent to participate: Not applicable. Consent for publication: All authors consent to the publication of this article. Competing interests: The authors declare no competing interests., (© 2025. The Author(s).)

Background: The detection of multiple bluetongue virus serotypes, increasing trend in livestock density, rich biological diversity with high endemism, and the status of the Andaman and Nicobar Islands as a popular tourist destination underscore the need for a faunistic survey of medically and veterinary significant vector species, specifically Culicoides, in this region. Moreover, scattered information on Indian Culicoides species complicates the planning and implementation of preventive measures for pathogens transmitted by these vectors. This study aims to provide the first comprehensive account of the Culicoides fauna in the Andaman and Nicobar Islands, India, along with an updated checklist of Indian Culicoides species and their state-wise distribution., Methods: Surveys were conducted across various habitats in the Andaman and Nicobar Islands in September 2022 and 2023. Midges were collected using CDC light traps, light sheets, Malaise traps, and manual collection from exposed body parts of the author and volunteers (biting collection). Identification was carried out using relevant taxonomic keys and original descriptions. Additionally, an updated checklist of Indian Culicoides, based on published and grey literature from 1910 to the present, is provided, with an emphasis on their potential role in pathogen transmission., Results: A total of 3529 adult Culicoides were trapped during the survey, representing 5 subgenera and 3 unplaced species groups. The study recorded 23 Culicoides species, including 13 new species records for India: C. barnetti, C. gouldi, C. flaviscutellaris, C. flavipunctatus, C. hui, C. histrio, C. guttifer, C. perornatus, C. okinawensis, C. quatei, C. obscurus, C. coronalis, and C. kusaiensis., Conclusions: The Indian Culicoides fauna now includes 93 valid species, with many of them recognized as confirmed or potential vectors of important pathogens of animal health. The enriched species composition highlights the importance of systematic surveys in this island ecosystem and the need to determine the role of midges, if any, in pathogen transmission., Competing Interests: Declarations. Ethics approval and consent to participate: Not applicable. Consent for publication: Not applicable. Competing interests: The authors declare no competing interests., (© 2024. The Author(s).)

Rapid urbanization and migration in Latin America have intensified exposure to insect-borne diseases. Malaria, Chagas disease, yellow fever, and leishmaniasis have historically afflicted the region, while dengue, chikungunya, and Zika have been described and expanded more recently. The increased presence of synanthropic vector species and spread into previously unaffected areas due to urbanization and climate warming have intensified pathogen transmission risks. This review examines recent outbreaks and reemergence of insect-borne diseases through five case studies: (i) malaria transmission linked to political instability and large-scale migration through the Amazon jungle; (ii) the expansion of triatomine bug habitats into overcrowded, substandard urban settlements, increasing Chagas disease incidence; (iii) the influence of movement and ecotourism in the Amazonia on yellow fever transmission in peri-urban areas; (iv) the spread of visceral leishmaniasis driven by deforestation and human-canine movement; and (v) dengue outbreaks in rural Amazon regions, spurred by urbanization and rural development. The findings underscore the complex interactions among vectors, pathogens, and shifting environmental and social conditions, complicating predictability and control. Addressing the social, economic, and political determinants of health is crucial to reducing disease transmission. Key measures include scaling vaccine coverage, especially for dengue and yellow fever; developing vaccines and treatments for neglected diseases; improving housing and sanitation; strengthening vector surveillance and control; fostering community engagement; enhancing data-driven interventions., Competing Interests: Declarations. Ethics approval and consent to participate: Not applicable. Consent for publication: Not applicable. Competing interests: Filipe Dantas-Torres is the Editor-in-Chief of Parasites & Vectors. This review was independently edited by Fredros Okumu (Subject Editor). The authors declare no further competing interests., (© 2025. The Author(s).)

Virus-derived small interfering RNAs (vsiRNAs) have been widely recognized to play an antiviral immunity role. However, it is unclear whether vsiRNAs can also play a positive role in viral infection. Here, we characterized three highly abundant vsiRNAs mapped to the genomic termini of rice stripe virus (RSV), a negative-strand RNA virus transmitted by insect vectors. The three vsiRNAs shared 11 nucleotides due to the conservative genomic termini and were likely generated from viral terminal panhandle structure, depending on both Dicer1 and Dicer2 in insects. In addition to targeting viral RNAs in a miRNA-like manner, the three vsiRNAs coordinately downregulated the expression of DOPA decarboxylase, thereby suppressing the prophenoloxidase immune reaction in insect vectors. In vsiRNA-silenced transgenic rice, the viral titer significantly decreased, indicating that these vsiRNAs promote RSV replication in rice. This study elucidates a unique function of vsiRNAs derived from the conserved panhandle structure of negative-strand RNA viruses in enhancing viral infection., Competing Interests: The authors declare no competing interests., (Copyright: © 2025 Zhao et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Zoos are considering to be essential places for the conservation of wild animal species. It is essential to prevent their infection by pathogens especially for those belonging to threatened or extinct species. Zoo captive animals are susceptible to several Culicoides and mosquito borne-viruses. In order to further evaluate the risk of pathogen transmission in zoos, it is essential to identify the presence of potential vector species, as well as the animals bitten by those vectors. For this purpose, Culicoides and mosquito species composition was investigated in ten sites from March to June 2021 for Culicoides (18 collection nights) and in four sites from April to June 2022 for mosquitoes (16 collection nights) at the National Zoological Garden of Rabat (ZGR), Morocco. Culicoides (Diptera: Ceratopogonidae) were collected using Onderstepoort Veterinary Institute traps (UV-light/suction traps (OVI type)), every two weeks. Mosquitoes (Diptera: Culicidae) were collected using BG-Pro mosquito trap (BGP) combined with a CO2 source as an attractant, on two consecutive days every two weeks. The blood meal of engorged Culicoides was amplified by PCR, sequenced, and blasted for host species identification. In total, 1584 individuals belonging to the Culicoides genus were collected (88.25 % females and 11.75 % males) belonging to at least 13 different species. Among the species collected, Culicoides newsteadi (33.28 %), C. imicola (23.74 %), C. circumscriptus (18.88 %) and C. obsoletus/C. scoticus (7.96 %) constituted the majority of the total catches. These species are proven or suspected vector species of bluetongue and African hose sickness viruses in the Mediterranean basin. For mosquitoes, 455 individuals belonging to four species of three genera were collected (97.58 % females and 2.42 % males): Culex pipiens s.l. (94.29 %) (vector species of West Nile and Rift Valley fever viruses), Culiseta longiareolata (4.81 %), Aedes detritus s.l. and Ae. caspius (representing together less than 1.00 %). The results of blood meal analyses revealed that Culicoides fed on humans (n = 7), camels (n = 2), and common eland (n = 2). The composition of Culicoides and mosquito fauna is characteristic of the Rabat region. The composition is thus mostly determined by the environment rather than by the animal species presence. The results highlighted that Culicoides fed on humans and ruminants. It is therefore likely that the zoo's animals could be threatened by arboviruses transmitted by domestic animals in the region. Particular attention must be paid to the prevention of vector-borne diseases to ensure the proper conservation of species., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Europe faces regular introductions and reintroductions of bluetongue virus (BTV) serotypes, most recently exemplified by the incursion of serotype 3 in the Netherlands. Although the long-distance wind dispersal of the disease vector, Culicoides spp., is recognized as a virus introduction pathway, it remains understudied in risk assessments. A Quantitative Risk Assessment framework was developed to estimate the risk of BTV-3 incursion into mainland Europe from Sardinia, where the virus has been present since 2018. We used an atmospheric transport model (HYbrid Single-Particle Lagrangian Integrated Trajectory) to infer the probability of airborne dispersion of the insect vector. Epidemiological disease parameters quantified the virus prevalence in vector population in Sardinia and its potential first transmission after introduction in a new area. When assuming a 24h maximal flight duration, the risk of BTV introduction from Sardinia is limited to the Mediterranean Basin, mainly affecting the southwestern area of the Italian Peninsula, Sicily, Malta, and Corsica. The risk extends to the northern and central parts of Italy, Balearic archipelago, and mainland France and Spain, mostly when maximal flight duration is longer than 24h. Additional knowledge on vector flight conditions and Obsoletus complex-specific parameters could improve the robustness of the model. Providing both spatial and temporal insights into BTV introduction risks, our framework is a key tool to guide global surveillance and preparedness against epizootics., (© 2024 The Author(s). Risk Analysis published by Wiley Periodicals LLC on behalf of Society for Risk Analysis.)

The Oropouche Virus (OROV) has Culicoides paraensis as its main vector in the urban cycle. Diagnoses of acute febrile cases and entomological collections were performed between January and April 2024 in the urban setting of Porto Velho, a city located in the western Brazilian Amazon. A total of 904 human samples were evaluated using RT-qPCR, of which 328 were positive for OROV. In addition, 3,950 insects were captured and Culex quinquefasciatus was the most abundant and predominant species. Seven mosquito samples showed amplification for OROV from pools of Cx. quinquefasciatus, Limatus durhamii and Aedes albopictus. Due to the first record of OROV in the two latter species, our findings can support new hypotheses about potential or bridge vectors. In turn, the high density of Cx. quinquefasciatus reinforces the supposition of this species as the main urban vector in the Amazon in the absence of C. paraensis. Complementary studies of vector competence and capacity are necessary for confirmation., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier B.V.)

Tomato spotted wilt virus (TSWV) is transmitted by insect pests from the Thripidae family, including Frankliniella occidentalis, commonly known as western flower thrips. For experimental purposes, researchers have developed methods for inoculating host plants with TSWV, allowing thrips to acquire TSWV, and verifying thrips acquisition. Plants can be inoculated with TSWV either mechanically or with thrips in the lab, but in nature, the virus is transmitted by thrips. For the study of tospovirus transmission biology and vector-virus interactions, efficient methods for mechanical and thrips transmission are essential. We have optimized these protocols for TSWV and western flower thrips, but they can also be adapted to other tospovirus-vector systems., (© 2025. The Author(s), under exclusive license to Springer Science+Business Media, LLC, part of Springer Nature.)

Soybean is one of the most valuable legume crops in the world. Soybean stay-green syndrome (SGS), which causes delayed leaf senescence (stay-green), flat pods, and abnormal seeds of soybean, has become one of the most serious diseases of soybean in the Huang-Huai-Hai Valley of China. However, the causal agent of SGS was controversial. Until recently, a newly evolved geminivirus with the unassigned genus in the family Geminiviridae, soybean stay-green associated geminivirus (SoSGV) was identified by several individual labs as one of the main causative agents of SGS. The epidemiological assessment reveals that SGS is prevalent in the field and is undergoing geographical expansion and genetic differentiation. The common brown leafhopper (Orosius orientalis) is considered the transmission vector of SoSGV. In this review, we discuss the biology and epidemiology of SoSGV and summarize its occurrence, distribution, and transmission in China, which would benefit further studies and support preventing and controlling this virus., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Toscana virus (TOSV), a member of the Phlebovirus genus transmitted by sandflies, is acknowledged for its capacity to cause neurological infections and is widely distributed across Mediterranean countries. The potential geographic distribution and risk to the human population remained obscure due to its neglected nature. We searched PubMed and Web of Science for articles published between 1 January 1971 and 30 June 2023 to extract data on TOSV detection in vectors, vertebrates and humans, clinical information of human patients, as well as the occurrence of two identified sandfly vectors for TOSV. We further predicted the global distribution of the two sandfly vectors, based on which the global risk of TOSV was projected, after incorporating the environmental, ecoclimatic, biological, and socioeconomic factors. A total of 1342 unique studies were retrieved, among which 389 met the selection criteria and were included for data extraction. TOSV infections were documented in 10 sandfly species and 14 species of vertebrates, as well as causing a total of 7571 human infections. The occurrence probabilities of two sandfly vectors have demonstrated the greatest contributions to the potential distribution of TOSV infection risk. This study provides a comprehensive overview of global TOSV distribution and potential risk zones. Future surveillance and intervention programs should prioritize high-risk areas based on updated quantitative analyses.

While a considerable number of viruses have been recently discovered in hematophagous insects, there remains insufficient research on virus diversity and their association with phytophagous insect hosts. In this study, we conducted a systematic investigation of the RNA virome in the small brown planthopper (SBPH), Laodelphax striatellus , an important vector of plant viruses. We successfully identified a total of 22 RNA viruses, including 17 novel viruses, from various families. These viruses were prevalent and abundant in SBPH populations, originating from the lab or field, with +ssRNA viruses composing the core SBPH viruses. Subsequent analysis revealed that the overall abundance of RNA viruses in SBPH remained relatively consistent across different developmental stages of the insects, although the titers of individual viruses varied among different insect tissues. This indicates a delicate balance between the viruses and their insect hosts. Interestingly, cross-species experiments confidently indicated that certain SBPH viruses could successfully infect and replicate in two other rice planthopper species (the brown planthopper and the white-backed planthopper) through microinjection. In conclusion, this study provides valuable insights into the RNA virome and its adaptability in a phytophagous insect, contributing to a better understanding of the intimate relationship between viruses and host insects., Importance: In the last decade, advances in the next-generation sequencing technology have unveiled a vast diversity of viruses in insects, particularly RNA viruses in hematophagous insects. However, research on virus diversity and their association with phytophagous insect hosts remains insufficient. This study presents a comprehensive analysis of the RNA virome in the small brown planthopper (SBPH), Laodelphax striatellus , a critical vector of plant viruses. The results indicated that the +ssRNA viruses, especially picorna-like viruses, comprised the core RNA viruses of SBPH that were prevalent in both laboratory and field populations. Moreover, a delicate balance was observed between the viruses and insect hosts. Significantly, some RNA viruses of SBPH could successfully infect and replicate in two other rice planthopper species belonging to different genera. This study provides valuable insights into the RNA virome and its adaptability in a phytophagous insect., Competing Interests: The authors declare no conflict of interest.

Musca domestica salivary gland hypertrophy virus (MdSGHV) affects house flies by enlarging salivary glands, impeding ovary development in females, and mating behavior in both males and females. It is not known if this virus impacts the quantity of saliva produced by house flies. This study aimed to establish baseline saliva quantities in healthy M. domestica across sexes and ages and examine how MdSGHV infection influences saliva output in 5-day-old males. Results reveal that healthy female Musca domestica produce more saliva on average than males and that saliva production among both sexes decreases with age. A comparison of infected, PBS-injected, and healthy flies shows significantly higher saliva quantities in infected individuals, suggesting MdSGHV enhances saliva production to improve transmission. These findings provide insights into MdSGHV transmission dynamics, which may provide for a better understanding of how other vector-borne diseases like Zika and Dengue virus interact in the infected salivary glands of the host vector.

The Bluetongue disease is an infectious and non-contagious viral disease mainly transmitted through hematophagous vector of the Culicoides genus, to domestic and wild ruminants. The aim of this study was to evaluate the antibodies occurrence, persistence and potential risk factors associated with bluetongue virus infection in sheep flocks in the state of Parana, Brazil. The competitive ELISA test was applied to evaluate 690 blood serum samples from 22 farms in eight mesoregions of Parana in 2014, and 270 sheep blood serum samples from 10 of the 22 previously studied farms in 2017. A questionnaire was applied to evaluate the risk factors associated with BTV infection. In 2014 and 2017, the numbers of seroreactive sheep were found to be 28.26% (195/690) and 41.11% (111/270), respectively, representing 95.45% (21/22) and 90% (9/10) of the flocks. The significant variables considered as risk factors were Culicoides presence (P < 0.0001; OR = 8.83 and 95% CI 4.28-18.22); genealogical record (P < 0.0001; OR = 0.23 and 95% CI 0.12-0.45) and use of sheepfold (P = 0.0208; OR = 0.36 and 95% CI 0.15-0 0.86). It was determined that BTV infection is endemic in Parana and persists in the mesoregions where the climate is favorable to vector proliferation., Competing Interests: Declarations. Conflict of interest: The authors have no relevant financial or non-financial interests to disclose. Ethics approval and consent to participate: The project underwent ethical review and was given approval by the institutional animal care and use committee from Ethics Committee on the use of animals (CEUA 006/16), following all the national/international guidance of animal experimentation., (© 2024. The Author(s) under exclusive licence to Sociedade Brasileira de Microbiologia.)

Sand flies (Diptera: Phlebotominae) are the principal vectors for the protozoan parasites Leishmania spp. and for phleboviruses. The sand fly fauna on the Balkan Peninsula, including Bosnia and Herzegovina (BIH), is diverse and the circulation of Leishmania infantum as well as phleboviruses has been proven. However, recent data on the sand fly fauna in BIH are scarce. In this study, we surveyed understudied regions in central and northeastern BIH to update the sand fly distribution and gain insights into the ecological and environmental factors shaping their appearance. CDC light trapping was conducted in 2022 and 2023 and a combination of morphological and molecular methods (cytochrome oxidase I barcoding) was performed for species identifications. We mapped the currently known distribution, modelled climatic suitability patterns and performed environmental analyses by applying machine learning methods. In addition, we analyzed blood meals by host gene sequencing and MALDI-TOF peptide mass mapping and screened for Leishmania spp. DNA and Phlebovirus RNA. Altogether, 591 sand flies of four species were trapped, predominantly Phlebotomus neglectus (97 %), but also Ph. balcanicus, Ph. mascittii, and Ph. papatasi. Records of seven sand fly species known to be endemic were plotted onto distribution maps based on 101 datapoints, identifying Ph. neglectus as the overall predominant species. The environmental analyses of sand fly species indicated variation in altitudinal, thermal, and precipitation conditions across the sand fly-positive sites. Phlebotomus simici, Phlebotomus tobbi, and Sergentomyia minuta are typically found exclusively in Mediterranean and subtropical climate zones, whereas other species typically inhabit continental regions. The Inverse Distance Weighted (IDW) interpolation of sand fly species numbers and Shannon entropy values suggested the southeastern coastal region of BIH as a primary focus for sand fly occurrence. This finding was corroborated by modeled average climatic suitability patterns for sand flies, depicting four distinct meso-regions for sand fly occurrence. The results of the ensemble method highlight the importance of annual precipitation to distinguish between positive and negative sand fly trapping sites in BIH. In total, 55 blood meals of two sand fly species, Ph. neglectus and Ph. balcanicus, were analyzed and five host species identified. Our comprehensive assessment of ecological and environmental preferences of sand flies in BIH may support further entomological surveys and help to better understand and evaluate potential hot spots of disease transmission in the country., Competing Interests: Declaration of competing interest The authors declare there are no competing interests associated with the manuscript., (Copyright © 2024 The Author(s). Published by Elsevier B.V. All rights reserved.)

Criniviruses are emerging pathogens responsible for significant disease outbreaks worldwide. Among them, blackberry yellow vein-associated virus (BYVaV) is prevalent in blackberry-producing areas of the United States and, when present in the blackberry yellow vein disease complex with other viruses, can lead to substantial crop losses. To better understand BYVaV biology and its role in virus complex disease development, we developed a BYVaV-derived infectious clone and a virus-induced gene silencing (VIGS) vector. The infectious clone successfully induced systemic infection and symptom development in Nicotiana benthamiana. Additionally, transmission of the recombinant virus to indicator plants was confirmed using the whitefly vector Trialeurodes vaporariorum. The infectious clone was subsequently modified into a VIGS vector, with the foreign insert remaining stable for the length of the study. This work provides essential tools for advancing the study of BYVaV biology and conducting genomic studies in its natural hosts., Competing Interests: Declaration of competing interest The authors declare that they do not have any conflicts of interest., (Copyright © 2024. Published by Elsevier B.V.)

Model forecasts of the spatiotemporal occurrence dynamics of diseases are necessary and can help understand and thus manage future disease outbreaks. In our study, we used ecological niche modelling to assess the impact of climate on the vector suitability for bluetongue disease, a disease affecting livestock production with important economic consequences. Specifically, we investigated the relationship between the occurrence of bluetongue outbreaks and the environmental suitability of each of the four vector species studied. We found that the main vector for bluetongue disease, Culicoides imicola, a typically tropical and subtropical species, was a strong predictor for disease outbreak occurrence in a region of southern Portugal from 2004 to 2021. The results highlight the importance of understanding the climatic factors that might influence vector presence to help manage infectious disease impacts. When diseases impact economically relevant species, the impacts go beyond mortality and have important economic consequences., (© 2024 Royal Entomological Society.)

Oropouche virus (OROV), an arbovirus belonging to the Orthobunyavirus genus and Peribunyaviridae family, is the causative agent of the so-called "sloth fever." The virus primarily relies on the midge vector Culicoides paraensis for transmission, maintaining both sylvatic and urban cycles. Human infections are characterized by acute febrile symptoms, and severe cases can lead to neurological complications. Since its first isolation in 1955, OROV has caused numerous outbreaks throughout South America, infecting over half a million people. Recent outbreaks in the Amazon and the Caribbean, along with cases reported in U.S. travellers, underscore the growing threat of OROV amid climate change and increased global travel. With no FDA-approved vaccines or specific antiviral treatments available, current management of the disease caused by OROV infection is limited to supportive care. The urgent need for effective vaccines is amplified by the potential for geographic expansion of the virus and its transmitting vector(s). The ongoing development of OROV vaccine candidates represents a crucial step towards controlling future OROV outbreaks and enhancing global public-health preparedness against this emerging infectious disease.

Many plant viruses modify the phenotype of their hosts, which may influence the behaviour of their vectors and facilitate transmission. Among them is the turnip yellows virus (TuYV), which can modify the orientation, feeding, and performance of its main aphid vector, Myzus persicae. However, the virus factors driving these mechanisms have not been elucidated. In this study, we compared the feeding behaviour and fecundity of aphids on TuYV-infected and transgenic Arabidopsis thaliana expressing individual TuYV proteins (CP, RT and P0) to define the role of these proteins in aphid-plant interactions. Aphids on TuYV-infected plants had shorter pathway phases and ingested phloem sap for longer times, which is expected to promote the acquisition of the phloem-limited TuYV. No change in aphid fecundity was observed on TuYV-infected plants. The transmission-conducive feeding behaviour changes could be fully reproduced by phloem-specific expression of the capsid protein (CP) in transgenic plants, whereas expression of P0 had minor and RT had no effects on aphid feeding behaviour. We then carried out a metabolomic analysis to determine plant compounds that could be involved in the modification of the aphid behaviour. A few metabolites were specific for TuYV-infected or CP-transgenic A. thaliana, and are good candidates for inducing behavioural changes., (© 2024 The Author(s). Plant, Cell & Environment published by John Wiley & Sons Ltd.)

The biting midges Culicoides Latreille, 1809 (Diptera: Ceratopogonidae) is highly relevant to epidemiology and public health, as it includes species that are potential vectors of human and animal arboviruses. The aim of this study was to investigate the presence of RNA viruses in species of the genus Culicoides collected in the Carajás mining complex in the state of Pará. The biting midges were collected in the municipalities of Canaã dos Carajás, Curionópolis and Marabá and morphologically identified. A total of 1139 specimens of seven Culicoides species were grouped into eight pools and subjected to metagenomic analysis. Eight new insect-specific viruses (ISVs) were characterized and assigned to the order Tolivirales , the families Chuviridae , Nodaviridae , Iflaviridae , Mesoniviridae , and Flaviviridae, and the taxon Negevirus . All viruses identified were assigned to clades, families and taxa never reported in Culicoides in Brazil. This study demonstrated that biting midges harbor a significant diversity of RNA viruses, many of which are still unknown, highlighting the importance of studies aiming at virome of these insects.

Background: The Antarctic environment is susceptible to the introduction of non-native species due to its unique ecosystem, which has evolved under geographical isolation and extreme climatic conditions over an extended period. The recent introduction of the non-native winter crane fly, Trichocera maculipennis, to maritime Antarctica may pose a potential threat to the Antarctic ecosystem. In this study, we evaluated the possibility of the mechanical transmission of viruses by T. maculipennis., Methods: We assessed the potential for the mechanical transmission of viruses using next-generation sequencing (NGS), quantitative PCR (qPCR), and virus isolation methods from T. maculipennis (Tm)-related samples (Tm body-wash fluid and Tm body-ground samples) collected from habitats and sewage treatment facilities located at three research stations in Antarctica., Results: Virome analysis detected the genomic fragments of human adenovirus (AdV) and human endogenous retrovirus (HERV) in Tm-related samples. These viruses are commonly found in human feces. In addition, plant viruses, such as pepper mild mottle virus (PMMoV) and cucumber green mottle mosaic virus (CGMMV), both known indicators of enteric viruses, were identified in all Tm-related samples, likely originating from wastewater. However, the low quantities of AdV and HERV genomes detected in Tm-related samples through qPCR, coupled with the non-viability of AdV in virus isolation tests, indicate that T. maculipennis has limited potential for mechanical transmission under the conditions in the studies., Conclusions: Our study represents the first evaluation of the potential risk of non-native species serving as vectors for viral pathogens in Antarctica. Although the viruses detected were in relatively low quantities and non-viable, this study highlights the importance of further evaluating the risks associated with non-native species, particularly as the likelihood of their introduction increases to Antarctica due to climate change and increased human activity., Competing Interests: Declarations. Ethics approval and consent to participate: Not applicable. Consent for publication: Not applicable. Competing interests: The authors declare no competing interests., (© 2024. The Author(s).)

Whiteflies (Bemisia tabaci) and the diseases they transmit are a major detriment to crop yields and a significant contributor to world hunger. The highly evolved interactions of host plant, phloem-feeding insect vector with endosymbionts and persistently transmitted virus represent a tremendous challenge for interdisciplinary study. Presented here is the establishment of a colony of axenic whiteflies on tissue-cultured plants. Efficient colony establishment was achieved by a surface sterilization of eggs laid on axenic phototrophically tissue-cultured plants. The transfer of emerging whiteflies through coupled tissue culture vessels to new axenic plants facilitates robust subculturing and produces hundreds of whitefly adults per month. Whitefly proliferation on more than two dozen plant species is shown as well as in vitro testing of whitefly preference for different plants. This novel multi-organism system provides the high-level of biocontainment required by Federal permitting to conduct virus transmission experiments. Axenic whitefly adults were able to acquire and transmit a begomovirus into tissue-cultured plants, indicating that culturable gut microorganisms are not required for virus transmission. The approach described enables a wide range of hypotheses regarding whitefly phytopathology without the expense, facilities, and contamination ambiguity associated with current approaches., Competing Interests: Declarations Competing interests The authors declare no competing interests., (© 2024. The Author(s).)

Vesicular stomatitis virus (VSV), comprising vesicular stomatitis New Jersey virus (VSNJV) and vesicular stomatitis Indiana virus (VSIV), emerges from its focus of endemic transmission in Southern Mexico to cause sporadic livestock epizootics in the Western United States. A dearth of information on the role of potential arthropod vectors in the endemic region hampers efforts to identify factors that enable endemicity and predict outbreaks. In a two-year, longitudinal study at five cattle ranches in Chiapas, Mexico, insect taxa implicated as VSV vectors (blackflies, sandflies, biting midges, and mosquitoes) were collected and screened for VSV RNA, livestock vesicular stomatitis (VS) cases were monitored, and serum samples were screened for neutralizing antibodies. VS cases were reported during the rainy ( n = 20) and post-rainy ( n = 2) seasons. Seroprevalence against VSNJV in adult cattle was very high (75-100% per ranch) compared with VSIV (0.6%, all ranches). All four potential vector taxa were sampled, and VSNJV RNA was detected in each of them (11% VSNJV-positive of 874 total pools), while VSIV RNA was only detected in four pools of mosquitoes. Our findings indicate that VSNJV is the dominant serotype across our sampling sites with a variety of potential insect vectors involved in its transmission throughout the year. Although no livestock cases were reported in Chiapas during the dry season, VSNJV was detected in insects during this period, suggesting that mechanisms other than transmission from livestock support VSV endemicity.

Multi-infection of plants by viruses is very common and can change drastically infection parameters such as virus accumulation, distribution, and vector transmission. Sugar beet is an important crop that is frequently co-infected by the polerovirus beet chlorosis virus (BChV) and the closterovirus beet yellows virus (BYV), both vectored by the green peach aphid ( Myzus persicae ). These phloem-limited viruses are acquired while aphids ingest phloem sap from infected plants. Here we found that co-infection decreased transmission of BChV by ~50% but had no impact on BYV transmission. The drastic reduction of BChV transmission was due to neither lower accumulation of BChV in co-infected plants nor reduced phloem sap ingestion by aphids from these plants. Using the signal amplification by exchange reaction fluorescent in situ hybridization technique on plants, we observed that 40% of the infected phloem cells were co-infected and that co-infection caused redistribution of BYV in these cells. The BYV accumulation pattern changed from distinct intracellular spherical inclusions in mono-infected cells to a diffuse form in co-infected cells. There, BYV co-localized with BChV throughout the cytoplasm, indicative of virus-virus interactions. We propose that BYV-BChV interactions could restrict BChV access to the sieve tubes and reduce its accessibility for aphids and present a model of how co-infection could alter BChV intracellular movement and/or phloem loading and reduce BChV transmission.IMPORTANCEMixed viral infections in plants are understudied yet can have significant influences on disease dynamics and virus transmission. We investigated how co-infection with two unrelated viruses, BChV and BYV, affects aphid transmission of the viruses in sugar beet plants. We show that co-infection reduced BChV transmission by about 50% without affecting BYV transmission, despite similar virus accumulation rates in co-infected and mono-infected plants. Follow-up experiments examined the localization and intracellular distribution of the viruses, leading to the discovery that co-infection caused a redistribution of BYV in the phloem vessels and altered its repartition pattern within plant cells, suggesting virus-virus interactions. In conclusion, the interplay between BChV and BYV affects the transmission of BChV but not BYV, possibly through direct or indirect virus-virus interactions at the cellular level. Understanding these interactions could be crucial for managing virus propagation in crops and preventing yield losses., Competing Interests: The authors declare no conflict of interest.

Dopamine (DA) is the most abundant biogenic amine present in the insect central nervous system, and regulates multiple functions in physiology and behaviors through dopamine receptors (DARs). The small brown planthopper Laodelphax striatellus is an important agricultural pest and causes serious damage by transmitting diverse plant viruses, such as rice stripe virus (RSV). However, DARs have not yet been molecularly characterized in planthoppers, and their roles in virus infection and transmission remain largely unknown in insect vectors. In this study, we cloned four LsDARs (LsDOP1, LsDOP2, LsDOP3 and LsDopEcR) from L.striatellus. LsDARs share considerable sequence identity with their orthologous DARs, and cluster nicely with their corresponding receptor groups. The transcript levels of LsDARs varied in different developmental stages and adult tissues, with the highest expressions in the egg stage and in the brain. The expression levels of LsDARs were significantly higher in RSV-viruliferous L.striatellus. Knockdown of LsDOP2 and LsDOP3 significantly downregulated the expressions of viral genes of capsid protein (CP) and RNA3 segment (RNA3), while LsDOP1 knockdown upregulated their expressions. Silencing LsDopEcR upregulated and then downregulated CP and RNA3 expressions. Moreover, LsDOP2 and LsDOP3 knockdown significantly decreased the vertical transmission rates of RSV. Meanwhile, DA injection promoted RSV transmission and accumulation. We further demonstrated that silencing of LsDARs significantly altered the expressions of vitellogenin (LsVg) and Vg receptor (LsVgR). Furthermore, the reproduction performance of L.striatellus was reduced by LsDOP2 and LsDOP3 knockdown, but increased by LsDopEcR knockdown, and not affected by LsDOP1 silencing. These results provide critical information concerning the roles of DARs in virus transmission and reproduction in L.striatellus, and open the way for the development of innovative strategies for planthopper control., Competing Interests: Declaration of competing interest The authors declare no competing financial interests., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Bluetongue virus (BT) is a vector-borne virus that causes a disease, called bluetongue, which results in significant economic loss and morbidity in sheep, cattle, goats and wild ungulates across all continents of the world except Antarctica. Despite the geographical breadth of its impact, most BT epidemiological models are informed by parameters derived from the 2006-2009 BTV-8 European outbreak. The aim of this study was to develop a highly adaptable model for BT which could be used elsewhere in the world, as well as to identify the parameters which most influence outbreak dynamics, so that policy makers can be properly informed with the most current information to aid in disease planning. To provide a framework for future outbreak modelling and an updated parameterisation that reflects natural variation in infections, a newly developed and parameterised two-host, two-vector species ordinary differential equation model was formulated and analysed. The model was designed to be adaptable to be implemented in any region of the world and able to model both epidemic and endemic scenarios. It was parameterised using a systematic literature review of host-to-vector and vector-to-host transmission rates, host latent periods, host infectious periods, and vaccine protection factors. The model was demonstrated using the updated parameters, with South Africa as a setting based on the Western Cape's known cattle and sheep populations, local environmental parameters, and Culicoides spp. presence data. The sensitivity analysis identified that the duration of the infectious period for sheep and cows had the greatest impact on the outbreak length and number of animals infected at the peak of the outbreak. Transmission rates from cows and sheep to C. imicola midges greatly influenced the day on which the peak of the outbreak occurred, along with the duration of incubation period, and infectious period for cows. Finally, the protection factor of the vaccine had the greatest influence on the total number of animals infected. This knowledge could aid in the development of control measures. Due to gradual climate and anthropological change resulting in alterations in vector habitat suitability, BT outbreaks are likely to continue to increase in range and frequency. Therefore, this research provides an updated BT modelling framework for future outbreaks around the world to explore transmission, outbreak dynamics and control measures., Competing Interests: Declaration of Competing Interest This manuscript has not been submitted to, nor is under review at, another journal or other publishing venue. The authors have no affiliation with any organization with a direct or indirect financial interest in the subject matter discussed in the manuscript., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Insect vectors significantly threaten global agriculture by transmitting numerous plant viruses. Various measures, from conventional insecticides to genetic engineering, are used to mitigate this threat. However, none provide complete resistance. Therefore, researchers are looking for novel control options. In recent years with the advancements in genomic technologies, genomes and transcriptomes of various insect vectors have been generated. However, the lack of knowledge about gene functions hinders the development of novel strategies to restrict virus spread. RNA interference (RNAi) is widely used to elucidate gene functions, but its variable efficacy hampers its use in managing insect vectors and plant viruses. Genome editing has the potential to overcome these challenges and has been extensively used in various insect pest species. This review summarizes the progress and potential of genome editing in plant virus vectors and its application as a functional genomic tool to elucidate virus-vector interactions. We also discuss the major challenges associated with editing genes of interest in insect vectors., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Hemipteran insects transmit viruses when infesting plants, during which vectors activate salicylic acid (SA)-regulated antiviral defenses. How vector-borne plant viruses circumvent these antiviral defenses is largely unexplored. During co-infections of begomoviruses and betasatellites in plants, betasatellite-encoded βC1 proteins interfere with SA signaling and reduce the activation of antiviral resistance. βC1 inhibits SA-induced degradation of NbNPR3 (Nicotiana benthamiana nonexpressor of pathogenesis-related genes 3), a negative regulator of SA signaling. βC1 does not bind directly to NbNPR3, but regulates NbNPR3 degradation via heat shock protein 90s (NbHSP90s). NbHSP90s bind to both NbNPR3 and βC1 and suppress SA signaling. This viral success strategy appears to be conserved as it is also documented for viral proteins encoded by two aphid-borne viruses. Our findings reveal an exquisite mechanism that facilitates the persistence of vector-borne plant viruses and provide important insights into the intricacies of the virus life cycle., (© 2024. The Author(s).)

Toscana virus (TOSV) is an emerging arthropod-borne virus (arbovirus) of medical importance that is increasing its range across much of the Mediterranean Basin, Europe and the Middle East. Transmitted by Phlebotomus spp. sand flies, it is the most clinically relevant sand fly-borne phlebovirus. Initially isolated in the Tuscany region of Central Italy, it has now been detected in multiple countries that surround this geographical area. Infection of the vertebrate host can cause fever and neurological disease, following the dissemination of the virus to the brain. The prevalence is high in some regions, with a notable percentage of individuals showing seroconversion. TOSV can be a leading cause of acute meningitis and encephalitis (AME) during the summer months. In this comprehensive review, we will focus on several key topics. We discuss how TOSV has spread to establish outbreaks of infection in both humans and animals around the Mediterranean and the wider region. Clinical aspects of TOSV infection in humans are described, along with the best standards in diagnosis. Finally, we focus our discussion on the role of the sand fly vector, describing their biology, vector competency, implications for putative vertebrate reservoirs, the effect of the climate emergency on sand fly distribution and the putative role that sand fly-derived salivary factors may have on modulating host susceptibility to TOSV infection.

As the most abundant and diverse groups of animals, insects play many important roles in the ecosystem, such as those of herbivores, vectors, and pollinators [...].

The majority of plant viruses rely on insect vectors for inter-plant transmission. Amid virus transmission, vector-borne viruses such as begomoviruses may significantly modulate host plants in various ways and, in turn, plant palatability to insect vectors. While many case studies on monopartite begomoviruses are available, bipartite begomoviruses are understudied. More importantly, detailed elucidation of the molecular mechanisms involved is limited. Here, we report the mechanisms by which an emerging bipartite begomovirus, the Sri Lankan cassava mosaic virus (SLCMV), modulates plant defenses against whitefly. SLCMV infection of tobacco ( Nicotiana tabacum ) plants significantly downregulated defenses against whitefly, as whitefly survival and fecundity increased significantly on virus-infected plants when compared to the controls. We then profiled SLCMV-induced transcriptomic changes in plants and identified a repertoire of differentially expressed genes (DEGs). GO enrichment analysis of DEGs demonstrated that the term defense response was significantly enriched. Functional analysis of DEGs associated with defense response revealed that four downregulated DEGs, including putative late blight resistance protein homolog R1B-17 ( R1B-17 ), polygalacturonase inhibitor-like ( PGI ), serine/threonine protein kinase CDL1-like ( CDL1 ), and Systemin B , directly contributed to plant defenses against whitefly. Taken together, our findings elucidate the role of novel plant factors involved in the modulation of plant defenses against whitefly by a bipartite begomovirus and shed new light on insect vector-virus-host plant tripartite interactions.

Beet curly top virus (BCTV, curtovirus , geminiviridae ) causes one of the most economically significant viral diseases in crops in the Western United States and is transmitted only by the beet leafhopper ( Circulifer tenellus ) in a non-propagative circulative manner. A better understanding of how this virus overcomes insect vector cellular barriers is essential to understanding virus-vector interactions. The distribution of BCTV in its beet leafhopper vector was investigated using immunofluorescence confocal laser scanning microscope analysis (iCLSM) on the whole-mount-dissected organs of leafhoppers. BCTV was localized in several lobes of the principal salivary glands, filter chamber, anterior midgut, and mid midgut, suggesting the occurrence of midgut and salivary gland barriers to BCTV transmission in its vector C. tenellus . This study also investigated the distribution of the chaperon GroEL homolog protein produced by primary endosymbiotic bacteria within the beet leafhopper, which is believed to indirectly affect viral transmission by enhancing insect immunity and resistance to viruses. GroEL was identified in leafhopper salivary glands lobes, the stylet, salivary canal, the filter chamber, and the Malpighian tubule. This is the first work to visualize the localization of a curtovirus within its beet leafhopper vector. Together, these results can help understand ssDNA virus-vector relationships, including cellular transmission barriers and other vector protein components.

Triatomines are infamous as vectors of the parasite Trypanosoma cruzi, the causative agent of Chagas disease. However, climate-driven range expansion and urbanization adaptation of triatomine populations, coupled with their highly diverse feeding strategies (vertebrate haematophagy, kleptohaematophagy, and coprophagy), and has elevated interest in triatomines as potential arboviral vectors. Information on the triatomine virome is scant, with prior records including only eight insect-specific viruses: Triatoma virus (TrV) and Rhodnius prolixus viruses 1-7. Here, we leverage publicly available transcriptome datasets to assess viral diversity in 122 wild and colony kissing bugs representing eight species from six countries. In total, six viruses were detected (including Rhodnius prolixus viruses 4-6), and TrV was detected in almost half of all screened triatomines. This is the first report of TrV in Triatoma brasiliensis and in members of the genus Mepraia (M. gajardoi, M. spinolai, and M. parapatrica), and this effort has vastly expanded the publicly available genomic resources of TrV, adding 39 genome sequences to the single genome sequence currently available in the GenBank database. Furthermore, two additional viruses-Meccus longipennis virus 1 and Drosophila melanogaster Nora virus-are herein reported for the first time from kissing bugs. Meccus longipennis virus 1 was detected in Triatoma infestans from Argentina, Brazil, Chile, and Peru, and Drosophila melanogaster Nora virus was found in T. infestans from Argentina. Our results illustrate the advantage and utility of low-cost transcriptome data mining for the discovery of known and novel arboviruses in triatomines and other potential insect vectors., (© 2024. The Author(s).)

Biting sandflies are known for transmitting leishmaniasis, but sandflies also transmit sandfly fever viruses that may disrupt military operations. Sandfly fever is caused by serotypes of the Phlebovirus genus (primarily the Naples, Sicilian, or Toscana serotypes). The illness is known colloquially as "three-day fever" and "papataci fever." The clinical course of the disease normally spans about 3 days, with patients exhibiting a prodromal phase consisting of fatigue, chills, abdominal pain, and possibly facial flushing and tachycardia. Disease onset is marked by hyperpyrexia, myalgia, and arthralgia. The incubation period is typically 3-5 days, with viremia in humans lasting typically less than 1 week. This manuscript describes sandfly appearance, behavior, and geographic distribution. It then lists comparable diseases for differential diagnosis. Finally, as no vaccine exists for the sandfly virus, it concludes with steps for preparation and prevention to prevent outbreaks from disrupting military operations., Competing Interests: The author has nothing to disclose., (2024.)

Common bean ( Phaseolus vulgaris L.) is a widely cultivated crop, representing an important protein source in the human diet in developing countries. The production of this crop faces serious challenges, such as virus diseases transmitted by the whitefly Bemisia tabaci . Although there is a lot of information about some of these viruses, most of what we know has been developed using model systems, such as tomato plants and tomato yellow leaf curl virus (TYLCV). There is still very little information on the most relevant common bean viruses, such as bean golden mosaic virus (BGMV), bean golden yellow mosaic virus (BGYMV), bean dwarf mosaic virus (BDMV), cowpea mild mottle virus (CPMMV), and bean yellow disorder virus (BnYDV). In this review, we discuss the available data in the most up-to-date literature and suggest future research avenues to contribute to the development of management tools for preventing or reducing the damage caused by viruses in this important crop.

Plant viruses threaten food security and are often transmitted by insect vectors. Non-persistently transmitted (NPT) plant viruses are transmitted almost exclusively by aphids. Because virions attach to the aphid's stylet (mouthparts) and are acquired and inoculated via brief epidermal probes, the aphid-virus interaction is highly transient, with a very short aphid virus retention time. Many NPT viruses manipulate their host plant's phenotype to change aphid behaviour to optimise virus transmission. Epidemiological models of this have overlooked a key feature of aphid NPT virus retention: probing or feeding on a plant causes aphids to lose the virus. Furthermore, experimental studies suggest aphids could possibly inoculate multiple healthy plants within one infective period if they do not feed. Consequences of this for virus manipulation of host plant phenotype have not been explored. Our new compartmental epidemiological model includes both behaviour-based aphid dispersal and infectivity loss rates, and the ability of infective aphids to probe multiple plants before virus loss. We use our model to explore how NPT virus-induced host phenotypes affect epidemic outcomes, comparing these results to representative previous models. We find that previous models behave fundamentally differently and underestimate the benefit of an 'attract-and-deter' phenotype, where the virus induces increased aphid attraction to infected plants but deters them from prolonged feeding. Our results also highlight the importance of characterising NPT virus retention upon the aphid during probing. Allowing for multiple infective probes increases disease incidence and the effectiveness of virus manipulation, with implications for epidemic prediction and control., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Falla, Cunniffe. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Flowering ginger ( Alpinia purpurata ) is economically and culturally important in Hawaii. In the past decade, a slow decline syndrome has impacted the production of this crop in the state. RNA sequencing analyses and virus indexing surveys were done on samples collected from four of the Hawaiian Islands. Viral sequences corresponding to six viruses were recovered from transcriptomic data from samples with virus-like symptoms. Canna yellow mottle virus (CaYMV, genus Badnavirus ) and two novel viruses, Alpinia vein clearing virus (ApVCV, genus Ampelovirus ) and Alpinia vein streaking virus (ApVSV, genus Betanucleorhabdovirus ), were found at a moderate incidence in diseased plants. Conversely, three other viruses, including the two potyviruses, banana bract mosaic virus and bean common mosaic virus, and a badnavirus, banana streak GF virus, were also found but at a low incidence. Virus detection in potential insect vectors and transmission assays identified the mealybug Planococcus citri as a vector of CaYMV and ApVCV, whereas the aphid Pentalonia caladii was identified as a vector of the novel ApVSV. Both P. citri and P. caladii are common pests of flowering ginger in Hawaii. Transmission of ApVSV was achieved using P. caladii colonies either established in the laboratory or naturally feeding on infected plants, although no transmission was obtained using viruliferous aphids originally reared on taro ( Colocasia esculenta ). Our study provides insights into the potential association between viral infections and the observed decline symptoms of flowering ginger in Hawaii. However, more definitive studies are needed to link single or mixed viral infections with decline symptoms., Competing Interests: The author(s) declare no conflict of interest.

Background: The complex interaction between plant viruses and their insect vectors is the basis for the epidemiology of plant viruses. The 'Vector Manipulation Hypothesis' (VMH) was proposed to demonstrate the evolution of strategies in plant viruses to enhance their transmission to new hosts through direct effects on insect vector behavior and/or physiology. However, the aphid vectors used in previous studies were mostly obtained by feeding on virus-infected plants and as a result, it was difficult to eliminate the confounding effects of infected host plants. Furthermore, the mechanisms of the direct effects of plant viruses on insect vectors have rarely been examined comprehensively., Results: We fed Sitobion avenae on an artificial diet infused with a purified suspension of Barley yellow dwarf virus (BYDV) PAV strain to obtain viruliferous aphids. We then examined their growth and reproduction performance, resistance to the parasitoid Aphidius gifuensis Ashmead, and feeding behavior. The results indicate that (1) viruliferous aphids had a shorter life span and a lower relative growth rate at the nymphal stage; (2) A. gifuensis had a lower parasitism rate, mummification rate, and emergence rate in viruliferous aphids; (3) Viruliferous aphids spent more time on non-probing and salivation behavior and had a shorter total duration of penetration and ingestion compared with healthy conspecifics., Conclusion: These results suggest that plant virus infection may directly alter vector fitness and behavior that improves plant virus transmission, but not vector growth. These findings highlight the mechanisms of VMH and the ecological significance of vector manipulation by plant viruses, and have implications for plant virus disease and vector management. © 2024 Society of Chemical Industry., (© 2024 Society of Chemical Industry.)

Aphids are phloem-feeding insects that reduce crop productivity due to feeding and transmission of plant viruses. When aphids disperse across the landscape to colonize new host plants, they will often probe on a wide variety of nonhost plants before settling on a host suitable for feeding and reproduction. There is limited understanding of the diversity of plants that aphids probe on within a landscape, and characterizing this diversity can help us better understand host use patterns of aphids. Here, we used gut content analysis (GCA) to identify plant genera that were probed by aphid vectors of potato virus Y (PVY). Aphids were trapped weekly near potato fields during the growing seasons of 2020 and 2021 in San Luis Valley in Colorado. High-throughput sequencing of plant barcoding genes, trnF and ITS2, from 200 individual alate (i.e., winged) aphids representing nine vector species of PVY was performed using the PacBio sequencing platform, and sequences were identified to genus using NCBI BLASTn. We found that 34.7% of aphids probed upon presumed PVY host plants and that two of the most frequently detected plant genera, Solanum and Brassica, represent important crops and weeds within the study region. We found that 75% of aphids frequently probed upon PVY nonhosts including many species that are outside of their reported host ranges. Additionally, 19% of aphids probed upon more than one plant species. This study provides the first evidence from high-throughput molecular GCA of aphids and reveals host use patterns that are relevant for PVY epidemiology., (© 2024 The Authors. Insect Science published by John Wiley & Sons Australia, Ltd on behalf of Institute of Zoology, Chinese Academy of Sciences.)

Insect vector-virus-plant interactions have important ecological and evolutionary implications. The constant struggle of plants against viruses and insect vectors has driven the evolution of multiple defense strategies in the host as well as counter-defense strategies in the viruses and insect vectors. Cotton leaf curl Multan virus (CLCuMuV) is a major causal agent of cotton leaf curl disease in Asia and is exclusively transmitted by the whitefly Bemisia tabaci. Here, we report that plants infected with CLCuMuV and its betasatellite CLCuMuB enhance the performance of the B. tabaci vector, and βC1 encoded by CLCuMuB plays an important role in begomovirus-whitefly-tobacco tripartite interactions. We showed that CLCuMuB βC1 suppresses the jasmonic acid signaling pathway by interacting with the subtilisin-like protease 1.7 (NtSBT1.7) protein, thereby enhancing whitefly performance on tobacco plants. Further studies revealed that in wild-type plants, NtSBT1.7 could process tobacco preprohydroxyproline-rich systemin B (NtpreproHypSysB). After CLCuMuB infection, CLCuMuB βC1 could interfere with the processing of NtpreproHypSysB by NtSBT1.7, thereby impairing plant defenses against whitefly. These results contribute to our understanding of tripartite interactions among virus, plant, and whitefly, thus offering ecological insights into the spread of vector insect populations and the prevalence of viral diseases., (© The Author(s) 2024. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

Toscana virus (TOSV) is a leading cause of summer viral meningitis in Southern Europe (Central Italy, south of France, Spain and Portugal) and can cause severe neurological cases. Within the Mediterranean basin, it is transmitted by hematophagous sand flies belonging to the Phlebotomus genus. Despite the identification of the primary TOSV vectors, the viral developmental cycle in vector species remains largely unknown. Limited research has been conducted on transmission dynamics and the vector competence and vectorial capacity of the principal TOSV vector, Phlebotomus perniciosus. In this context, we investigated the intra-vector TOSV infection dynamics in Ph. perniciosus, as well as its impact on the vector life history traits. Female sand flies were experimentally infected with TOSV through an artificial blood meal. Systemic dissemination of the virus was observed approximately three days post-infection, potentially resulting in a short extrinsic incubation period. Moreover, the study revealed a longer hatching time for eggs laid by infected females. This research brought additional experimental insights regarding the vector competence of Ph. perniciosus but also provided the first insight into TOSV developmental cycle and its impact on the vector. These findings prompt further exploration of TOSV transmission dynamics, raise new hypotheses on the virus transmission and highlight the importance of follow-up studies., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Laroche et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

The plant virus, Impatiens necrotic spot virus (INSV), is an economically important pathogen of vegetables, fruits, and ornamental crops. INSV is vectored by the western flower thrips, Frankliniella occidentalis, a small insect pest that is globally distributed. In recent years, INSV outbreaks have reached epidemic levels in the Salinas Valley of California-an agriculturally rich region where most of the lettuce (Lactuca sativa) is produced in the United States. Due to the obligate nature in which virus transmission occurs, new tools that could rapidly detect INSV from thrips vectors would enhance our ability to predict where virus outbreaks may occur. Here, we report on the development of a reverse transcription-recombinase polymerase amplification (RT-RPA) assay that can detect INSV from individual thrips. The assay uses crude extraction methods, is performed at a single temperature of 42 °C, can be completed in 25 min, and provides sensitivity levels that are comparable to other available detection methods. When the assay was used on field populations of thrips, INSV was successfully identified and quantified from individual larvae and adults. The work provides a new cost-effective surveillance tool that can rapidly detect INSV from its insect vector and from plants., (© 2024. This is a U.S. Government work and not under copyright protection in the US; foreign copyright protection may apply.)

Dengue virus (DENV) is the most prevalent mosquito-borne Flavivirus that affects humans worldwide. Aedes albopictus, which is naturally infected with the bacteria Wolbachia, is considered to be a secondary vector of DENV. However, it was responsible for a recent DENV outbreak of unprecedented magnitude in Reunion Island, a French island in the South West Indian Ocean. Moreover, the distribution of the cases during this epidemic showed a spatially heterogeneous pattern across the island, leading to questions about the differential vector competence of mosquito populations from different geographic areas. The aim of this study was to gain a better understanding of the vector competence of the Ae. albopictus populations from Reunion Island for local DENV epidemic strains, while considering their infection by Wolbachia. Experimental infections were conducted using ten populations of Ae. albopictus sampled across Reunion Island and exposed to three DENV strains: one strain of DENV serotype 1 (DENV-1) and two strains of DENV serotype 2 (DENV-2). We analyzed three vector competence parameters including infection rate, dissemination efficiency and transmission efficiency, at different days post-exposition (dpe). We also assessed whether there was a correlation between the density of Wolbachia and viral load/vector competence parameters. Our results show that the Ae. albopictus populations tested were not able to transmit the two DENV-2 strains, while transmission efficiencies up to 40.79% were observed for the DENV-1 strain, probably due to difference in viral titres. Statistical analyses showed that the parameters mosquito population, generation, dpe and area of sampling significantly affect the transmission efficiencies of DENV-1. Although the density of Wolbachia varied according to mosquito population, no significant correlation was found between Wolbachia density and either viral load or vector competence parameters for DENV-1. Our results highlight the importance of using natural mosquito populations for a better understanding of transmission patterns of dengue., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Hafsia et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Bluetongue (BT) is a Culicoides midge-borne hemorrhagic disease affecting cervids and ruminant livestock species, resulting in significant economic losses from animal production and trade restrictions. Experimental animal infections using the α/β interferon receptor knockout IFNAR mouse model and susceptible target species are critical for understanding viral pathogenesis, virulence, and evaluating vaccines. However, conducting experimental vector-borne transmission studies with the vector itself are logistically difficult and experimentally problematic. Therefore, experimental infections are induced by hypodermic injection with virus typically derived from baby hamster kidney (BHK) cells. Unfortunately, for many U.S. BTV serotypes, it is difficult to replicate the severity of the disease seen in natural, midge-transmitted infections by injecting BHK-derived virus into target host animals. Using the IFNAR BTV murine model, we compared the virulence of traditional BHK cell-derived BTV-17 with C. sonorensis midge (W8) cell-derived BTV-17 to determine whether using cells of the transmission vector would provide an in vitro virulence aspect of vector-transmitted virus. At both low and high doses, mice inoculated with W8-BTV-17 had an earlier onset of viremia, earlier onset and peak of clinical signs, and significantly higher mortality compared to mice inoculated with BHK-BTV-17. Our results suggest using a Culicoides W8 cell-derived inoculum may provide an in vitro vector-enhanced infection to more closely represent disease levels seen in natural midge-transmitted infections while avoiding the logistical and experimental complexity of working with live midges.

Systemic viral infection of insects typically begins with the primary infection of midgut epithelial cells (enterocytes) and subsequent transit of the progeny virus in an apical-to-basal orientation into the hemocoel. For insect-vectored viruses, an oppositely oriented process (basal-to-apical transit) occurs upon secondary infection of salivary glands and is necessary for virus transmission to non-insect hosts. To examine this inversely oriented virus transit in these polarized tissues, we assessed the intracellular trafficking of two model viral envelope proteins (baculovirus GP64 and vesicular stomatitis virus G) in the midgut and salivary gland cells of the model insect, Drosophila melanogaster . Using fly lines that inducibly express either GP64 or VSV G, we found that each protein, expressed alone, was trafficked basally in midgut enterocytes. In salivary gland cells, VSV G was trafficked apically in most but not all cells, whereas GP64 was consistently trafficked basally. We demonstrated that a YxxØ motif present in both proteins was critical for basal trafficking in midgut enterocytes but dispensable for trafficking in salivary gland cells. Using RNAi, we found that clathrin adaptor protein complexes AP-1 and AP-3, as well as seven Rab GTPases, were involved in polarized VSV G trafficking in midgut enterocytes. Our results indicate that these viral envelope proteins encode the requisite information and require no other viral factors for appropriately polarized trafficking. In addition, they exploit tissue-specific differences in protein trafficking pathways to facilitate virus egress in the appropriate orientation for establishing systemic infections and vectoring infection to other hosts., Importance: Viruses that use insects as hosts must navigate specific routes through different insect tissues to complete their life cycles. The routes may differ substantially depending on the life cycle of the virus. Both insect pathogenic viruses and insect-vectored viruses must navigate through the polarized cells of the midgut epithelium to establish a systemic infection. In addition, insect-vectored viruses must also navigate through the polarized salivary gland epithelium for transmission. Thus, insect-vectored viruses appear to traffic in opposite directions in these two tissues. In this study, we asked whether two viral envelope proteins (VSV G and baculovirus GP64) alone encode the signals necessary for the polarized trafficking associated with their respective life cycles. Using Drosophila as a model to examine tissue-specific polarized trafficking of these viral envelope proteins, we identified one of the virus-encoded signals and several host proteins associated with regulating the polarized trafficking in the midgut epithelium., Competing Interests: The authors declare no conflict of interest.

Classification of mosquitoes with overlapping features remains problematic when using traditional morphological identification alone. In this study, we used molecular methods to elucidate the taxonomic status of Culex tritaeniorhynchus, Culex annulus, and Culex pseudovishnui species as vectors of the Japanese encephalitis virus belonging to the Culex vishnui subgroup and gene flow among them. In this study, 76, 59, and 3 samples of Cx. annulus, Cx. tritaeniorhynchus, and Cx. pseudovishnui, respectively, were collected around Taiwan. Phylogenetic analysis and genetic divergence were based on genomic sequence variations in ribosomal DNA and the internal transcribed spacer (rDNA) and cytochrome c oxidase subunit I (COI). Our results revealed that Cx. annulus and Cx. vishnui are genetically similar and share a gene pool among the species from Taiwan and other Asian countries. However, two hidden taxa of Cx. tritaeniorhynchus, which clustered together according to the rDNA sequences, were discovered based on the COI sequences. In addition, Cx. pseudovishnui has different gene pools from those of the strains from other countries, implying that the population from Taiwan is probably either a unique strain or a sibling species. This study provides molecular information on the taxonomic status of the species in the Cx. vishnui subgroup in Taiwan and gene flow between these species, providing valuable information for vector control operations and the delineation of the evolutionary process.

Plant jasmonoyl-L-isoleucine (JA-Ile) is a major defense signal against insect feeding, but whether or how insect salivary effectors suppress JA-Ile synthesis and thus facilitate viral transmission in the plant phloem remains elusive. Insect carboxylesterases (CarEs) are the third major family of detoxification enzymes. Here, we identify a new leafhopper CarE, CarE10, that is specifically expressed in salivary glands and is secreted into the rice phloem as a saliva component. Leafhopper CarE10 directly binds to rice jasmonate resistant 1 (JAR1) and promotes its degradation by the proteasome system. Moreover, the direct association of CarE10 with JAR1 clearly impairs JAR1 enzyme activity for conversion of JA to JA-Ile in an in vitro JA-Ile synthesis system. A devastating rice reovirus activates and promotes the co-secretion of virions and CarE10 via virus-induced vesicles into the saliva-storing salivary cavities of the leafhopper vector and ultimately into the rice phloem to establish initial infection. Furthermore, a virus-mediated increase in CarE10 secretion or overexpression of CarE10 in transgenic rice plants causes reduced levels of JAR1 and thus suppresses JA-Ile synthesis, promoting host attractiveness to insect vectors and facilitating initial viral transmission. Our findings provide insight into how the insect salivary protein CarE10 suppresses host JA-Ile synthesis to promote initial virus transmission in the rice phloem., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Vesicular stomatitis (VS) is a viral disease that affects horses, cattle, and swine that is transmitted by direct contact and hematophagous insects. In 2023, a multi-state outbreak of vesicular stomatitis New Jersey virus (VSNJV) occurred in California, Nevada, and Texas, infecting horses, cattle, and rhinoceros. To identify possible insect vectors, we conducted insect surveillance at various locations in San Diego County, CA, including at a wildlife park. CO 2 baited traps set from mid-May to mid-August 2023 collected 2357 Culicoides biting midges and 1215 Simulium black flies, which are insect genera implicated in VSNJV transmission. Insects were pooled by species, location, and date, then tested for viral RNA. Nine RNA-positive pools of Culicoides spp. and sixteen RNA-positive pools of Simulium spp were detected. Infectious virus was detected by cytopathic effect in 96% of the RNA-positive pools. This is the first report of VSNJV in wild-caught C. bergi , C. freeborni , C. occidentalis , S. argus , S. hippovorum , and S. tescorum. The vector competency of these species for VSNJV has yet to be determined but warrants examination. Active vector surveillance and testing during disease outbreaks increases our understanding of the ecology and epidemiology of VS and informs vector control efforts.