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Purpose: To provide an overview of pre-selected emerging arboviruses (arthropod-borne viruses) that cause ocular inflammation in humans. Methods: A comprehensive review of the literature published between 1997 and 2023 was conducted in PubMed database. We describe current insights into epidemiology, systemic and ocular manifestations, diagnosis, treatment, and prognosis of arboviral diseases including West Nile fever, Dengue fever, Chikungunya, Rift Valley fever, Zika, and Yellow fever. Results: Arboviruses refer to a group of ribonucleic acid viruses transmitted to humans by the bite of hematophagous arthropods, mainly mosquitoes. They mostly circulate in tropical and subtropical zones and pose important public health challenges worldwide because of rising incidence, expanding geographic range, and occurrence of prominent outbreaks as a result of climate change, travel, and globalization. The clinical signs associated with infection from these arboviruses are often inapparent, mild, or non-specific, but they may include serious, potentially disabling or life-threatening complications. A wide spectrum of ophthalmic manifestations has been described including conjunctival involvement, anterior uveitis, intermediate uveitis, various forms of posterior uveitis, maculopathy, optic neuropathy, and other neuro-ophthalmic manifestations. Diagnosis of arboviral diseases is confirmed with either real time polymerase chain reaction or serology. Management involves supportive care as there are currently no specific antiviral drug options. Corticosteroids are often used for the treatment of associated ocular inflammation. Most patients have a good visual prognosis, but there may be permanent visual impairment due to ocular structural complications in some. Community-based integrated mosquito management programs and personal protection measures against mosquito bites are the best ways to prevent human infection and disease. Conclusion: Emerging arboviral diseases should be considered in the differential diagnosis of ocular inflammatory conditions in patients living in or returning from endemic regions. Early clinical consideration followed by confirmatory testing can limit or prevent unnecessary treatments for non-arboviral causes of ocular inflammation. Prevention of these infections is crucial. [ABSTRACT FROM AUTHOR]

We conducted a large-scale survey of arboviruses in mosquitoes and biting midges to assess the presence and spread of mosquito-borne pathogens currently circulating on Hainan Island, China. RT-PCR assays were used to detect the arbovirus species, distribution, and infection rates in mosquitoes and biting midges. Cell inoculation and high throughput sequencing were performed to isolate the viruses and assemble full viral genomes. Phylogenetic analysis was conducted to identify the viral genotypes and evolutionary relationships with known viruses. During 2019–2023, 32,632 mosquitoes and 21,000 biting midges were collected from 14 of 18 cities/counties on Hainan Island. Japanese encephalitis virus (JEV) was detected in Culex mosquitoes from five cities/counties, where the minimum infection rate (MIR) was 1.6 (0.6–2.6) per 1,000 females tested. Tembusu virus (TMUV) was detected in Culex mosquitoes from three cities/counties with MIR1.0 (0–2.2) per 1,000. Getah virus (GETV) was detected in Armigeres mosquitoes from Qionghai city with MIR 7.1 (0–15.2) per 1,000. Oya virus (OYAV) and Bluetongue virus (BTV) were detected in biting midges from Wanning city with MIRs of 0.4 (0–1.2) and 0.1 (0–10.2) per 1,000, respectively. Three JEV strains were isolated and clustered within the genotype I group, which is presently the dominant genotype in China. Three TMUV strains were isolated for the first time on Hainan Island that belonged to Cluster 3. Three isolated GETVs were identified as Group 3. BTV was reported for the first time on Hainan Island, and the complete genome for one BTV strain was successfully assembled, which was classified as serotype 1 based on the sequences of segment 2. These results stress the need to develop adequate surveillance plan measures to better control the public health threat of arboviruses carried by mosquitoes and biting midges in local regions. Author summary: In the early 1990s, a large-scale survey for arboviruses in vectors was conducted in Hainan Island. However, in the past 30 years, with climate change, urbanization, and the increasing population and trades, whether the arboviruses spectrum changed on this Island is unclear. We screened arboviruses in mosquitoes and biting midges from 2019 to 2023 to assess the presence of arbovirus and the genetic evolution currently circulating on this Island. Except for arboviruses such as JEV, GTEV, and OYAV, which have been previously reported circulating on Hainan Island, TMUV and BTV were detected for the first time during this survey. These findings highlight the increasing risk of arbovirus transmission in Hainan Island. It is crucial to prioritize extensive and continuous surveillance of arboviruses carried by mosquitoes and biting midges in local regions to help prevent the spread of emerging and re-emerging arboviral diseases. [ABSTRACT FROM AUTHOR]

Aedes aegypti is an important vector of arboviruses, including dengue, chikungunya and Zika. The application of synthetic insecticides is a frequently used strategy to control this insect. Malathion is an organophosphate insecticide that was widely used in Brazil in the 1980s and 1990s to control the adult form of A. aegypti. In situations where resistance to currently used insecticides is detected, the use of malathion may be resumed as a control measure. Many studies have confirmed resistance to malathion, however, comparative studies of differential gene expression of the entire transcriptome of resistant and susceptible insects are scarce. Therefore, understanding the molecular basis of resistance to this insecticide in this species is extremely important. In this paper, we present the first transcriptomic description of susceptible and resistant strains of A. aegypti challenged with malathion. Guided transcriptome assembly resulted in 39,904 transcripts, where 2133 differentially expressed transcripts were detected, and three were validated by RT-qPCR. Enrichment analysis for these identified transcripts resulted in 13 significant pathways (padj < 0.05), 8 associated with down-regulated and 5 with up-regulated transcripts in treated resistant insects. It was possible to divide the transcripts according to the mechanism of action into three main groups: (i) genes involved in detoxification metabolic pathways; (ii) genes of proteins located in the membrane/extracellular region; and (iii) genes related to DNA integration/function. These results are important in advancing knowledge of genes related to resistance mechanisms in this insect, enabling the development of effective technologies and strategies for managing insecticide resistance. [ABSTRACT FROM AUTHOR]

The increasing spread of mosquito vectors has made mosquito-borne arboviral diseases a global threat to public health, leading to the urgent need for effective population control methods. Strategies based in the intracellular bacterium Wolbachia Hertig, 1936 are considered environmentally friendly, safe for humans, and potentially cost-effective for controlling arboviral diseases. To minimize undesirable side effects, it is relevant to assess whether Wolbachia is present in the area and understand the diversity associated with native infections before implementing these strategies. With this purpose, we investigated Wolbachia infection status, diversity, and prevalence in populations of Aedes albifasciatus (Macquart, 1838), Aedes fluviatilis (Lutz, 1904), and hybrids of the Culex pipiens (Linnaeus, 1758) complex from Argentina. Aedes albifasciatus and C. pipiens complex samples were collected in the province of Buenos Aires, and A. fluviatilis in the province of Misiones. Aedes albifasciatus was found to be uninfected, while infections with strains wFlu and wPip were detected in A. fluviatilis and hybrids of the C. pipiens complex, respectively. All strains were fixed or close to fixation and clustered within supergroup B. These finding provides valuable information on Wolbachia strains found in natural mosquito populations in Argentina that might be used in heterologous infections in the future or be considered when designing control strategies based on Wolbachia infection. [ABSTRACT FROM AUTHOR]

The RNA genome of orthoflaviviruses encodes a methyltransferase within the non-structural protein NS5, which is involved in 2'-O-methylation of the 5'-terminal nucleotide of the viral genome resulting in a cap1 structure. While a 2'-O-unmethylated cap0 structure is recognized in vertebrates by the RNA sensor RIG-I, the cap1 structure allows orthoflaviviruses to evade the vertebrate innate immune system. Here, we analyzed whether the cap0 structure is also recognized in mosquitoes. Replication analyses of 2'-O-methyltransferase deficient yellow fever virus mutants (YFV NS5-E218A) of the vaccine 17D and the wild-type Asibi strain in mosquito cells revealed a distinct downregulation of the cap0 viruses. Interestingly, the level of inhibition differed for various mosquito cells. The most striking difference was found in Aedes albopictus-derived C6/36 cells with YFV-17D cap0 replication being completely blocked. Replication of YFV-Asibi cap0 was also suppressed in mosquito cells but to a lower extent. Analyses using chimeras between YFV-17D and YFV-Asibi suggest that a synergistic effect of several mutations across the viral genome accompanied by a faster initial growth rate of YFV-Asibi cap1 correlates with the lower level of YFV-Asibi cap0 attenuation. Viral growth analyses in Dicer-2 knockout cells demonstrated that Dicer-2 is entirely dispensable for attenuating the YFV cap0 viruses. Translation of a replication-incompetent cap0 reporter YFV-17D genome was reduced in mosquito cells, indicating a cap0 sensing translation regulation mechanism. Further, oral infection of Aedes aegypti mosquitoes resulted in lower infection rates for YFV-Asibi cap0. The latter is related to lower viral loads found in the midguts, which largely diminished dissemination to secondary tissues. After intrathoracic infection, YFV-Asibi cap0 replicated slower and to decreased amounts in secondary tissues compared to YFV-Asibi cap1. These results suggest the existence of an ubiquitously expressed innate antiviral protein recognizing 5'-terminal RNA cap-modifications in mosquitoes, both in the midgut as well as in secondary tissues. Author summary: Arthropod-borne viruses infect both mosquito and vertebrate hosts. One factor influencing the level of viral replication in the host is the ability of the virus to evade or counteract the host's immune system. In vertebrates, it was shown that orthoflaviviruses circumvent the innate immune system by capping their viral genome with a cap1 structure characterized by 2'-O-methylation of the 5'-terminal nucleotide. In contrast, viral genomes lacking 2'-O-methylation (cap0) are recognized as foreign and activate the vertebrate innate immune system. Here, we used yellow fever virus (YFV) strain 17D and Asibi mutants lacking 2'-O-methylation, as well as a cap0 reporter YFV genome, to analyze cap0 recognition in mosquito cells and living mosquitoes. The replication of the YFV cap0 mutants was profoundly impaired in different mosquito cells and cap0 YFV genomes showed reduced translation levels. Based on viral infection experiments in Aedes aegypti mosquitoes, we further demonstrate that these vector mosquitoes recognize the cap0 structure and that a potential recognizing effector protein is localized in the midgut as well as in secondary tissues. Our findings provide the basis for future studies investigating the recognition of foreign RNAs in mosquitoes and should contribute to establish methods to prevent transmission of arboviruses. [ABSTRACT FROM AUTHOR]

Mosquitoes serve as vectors for many arthropod-borne viruses (arboviruses) that are responsible for millions of human infections and thousands of deaths each year. Among these arboviruses, O'nyong-nyong virus (ONNV) is an African alphavirus mainly transmitted by Anopheles mosquitoes. ONNV can be detected through serological or molecular tests, the first showing cross-reactivity to co-circulating alphaviruses and requiring technically demanding confirmation, while the latter, usually based on real-time PCR, are costly and demand specific equipment. Isothermal amplification approaches, such as Loop-Mediated Isothermal Amplification (LAMP), should therefore provide a cost-effective, sensitive, and specific alternative for virus detection, suitable for the resource-limited regions where ONNV circulates up to the present time. Here, we describe the development and optimization of a rapid and highly sensitive (10 pfu/reaction) RT-LAMP assay for ONNV detection. Additionally, we demonstrate that it is possible to bypass the RNA extraction step, reducing sample handling time and costs. The final RT-LAMPONNV is a promising field detection tool for ONNV, enabling a better understanding of its impact and serving as a point-of-care diagnostic method. [ABSTRACT FROM AUTHOR]

Arthropod-borne rickettsioses comprise a wide variety of subtypes that are endemic in Cambodia, but there remains very little data on the geographic distribution of the pathogens or their vectors. Surveys were conducted in Koh Kong and Preah Sihanouk Provinces between September 2017 and June 2018 to collect ectoparasites from peridomestic animals and the environment using dragging and flagging methods. Collected ectoparasites were sorted and identified morphologically, then pooled by species, host, and location for molecular detection using Rickettsia genus- and species-specific qPCR and/or multilocus sequence typing (MLST) assays. A total of 14,254 ectoparasites were collected including seven new locality records. Rickettsia species were detected in 35.5% (174/505) of the pools screened representing 3,149 randomly selected ectoparasites from the total collected. Rickettsia asembonensis was detected in 89.6% (147/164) of Rickettsia-positive flea pools and 3.6% (6/164) of the flea pools were positive for both R. asembonensis and Rickettsia felis. Candidatus Rickettsia senegalensis from Ctenocephalides orientis fleas and Rickettsia sp. close to Rickettsia japonica and Rickettsia heilongjiangensis from Haemaphysalis ticks were identified by MLST. This appears to be the first report of these new ectoparasite records and rickettsial species in southern Cambodia, suggesting a potential health risk to military and civilians in this region. Author summary: Rickettsiae are Gram-negative bacteria that cause acute undifferentiated febrile illness in humans. These pathogens are associated with arthropods and primarily transmitted by ectoparasites such as ticks, fleas, and mites. In Cambodia, rickettsial diseases have been documented in local patients, travelers and military personnel. However, the lack of entomological studies and awareness of these diseases hindered our comprehensive understanding of these pathogens and their arthropod vectors. Our manuscript provides a description of ectoparasite diversity and sheds light on their potential role in rickettsial disease transmission. Through molecular techniques, we uncover the prevalence and diversity of Rickettsia species in ectoparasites collected from various animal hosts in Koh Kong and Preah Sihanouk province. Rickettsia asembonensis, Rickettsia felis, and Candidatus Rickettsia senegalensis were all identified from Ctenocephalides orientis fleas, while Rickettsia species closely related to Rickettsia japonica, Rickettsia heilongjiangensis, and Rickettsia raoultii were found from Haemaphysalis ticks. Additionally, Rickettsia were also detected in Heterodoxus spiniger lice and Laelapidae mites, although we were unable to characterize the species. Insights into this pathogen-vector-host interface will better inform healthcare professionals, leading to more accurate diagnoses and increased awareness for better management of these diseases. [ABSTRACT FROM AUTHOR]

Mosquito-borne diseases such as dengue and filariasis are a growing public health concern in endemic countries. Biological approaches, such as the trans-infection of Wolbachia pipientis in mosquitoes, are an alternative vector control strategy, especially for arthropod-borne viruses such as dengue. In the present study, the effect of Wolbachia (wMel strain) on the vectorial capacity of Aedes aegypti for Dirofilaria immitis was studied. Our results showed that Wolbachia does not affect the phenotype of mosquito survival or the prevalence, number, and molting rate of third-stage larvae in both susceptible and resistant strains of Ae. aegypti. RNA-seq analysis of Malpighian tubules at 2 days post-infection with D. immitis showed the differentially expressed genes (DEGs) with and without wMel infection. No characteristic immune-related gene expression patterns were observed among the DEGs. No significant change in the amount of Wolbachia was observed in the Ae. aegypti after D. immitis infection. Our results suggest that infection of D. immitis in Ae. aegypti populations will not interfere with Wolbachia-based vector control strategies in dengue-endemic areas where cases of D. immitis are present. This study demonstrated the veterinary medical validity of a dengue control program using Wolbachia. [ABSTRACT FROM AUTHOR]

Background: The effectiveness of dengue control interventions depends on an effective integrated surveillance system that involves analysis of multiple variables associated with the natural history and transmission dynamics of this arbovirus. Entomological indicators associated with other biotic and abiotic parameters can assertively characterize the spatiotemporal trends related to dengue transmission risk. However, the unpredictability of the non-linear nature of the data, as well as the uncertainty and subjectivity inherent in biological data are often neglected in conventional models. Methods: As an alternative for analyzing dengue-related data, we devised a fuzzy-logic approach to test ensembles of these indicators across categories, which align with the concept of degrees of truth to characterize the success of dengue transmission by Aedes aegypti mosquitoes in an endemic city in Brazil. We used locally gathered entomological, demographic, environmental and epidemiological data as input sources using freely available data on digital platforms. The outcome variable, risk of transmission, was aggregated into three categories: low, medium, and high. Spatial data was georeferenced and the defuzzified values were interpolated to create a map, translating our findings to local public health managers and decision-makers to direct further vector control interventions. Results: The classification of low, medium, and high transmission risk areas followed a seasonal trend expected for dengue occurrence in the region. The fuzzy approach captured the 2020 outbreak, when only 14.06% of the areas were classified as low risk. The classification of transmission risk based on the fuzzy system revealed effective in predicting an increase in dengue transmission, since more than 75% of high-risk areas had an increase in dengue incidence within the following 15 days. Conclusions: Our study demonstrated the ability of fuzzy logic to characterize the city's spatiotemporal heterogeneity in relation to areas at high risk of dengue transmission, suggesting it can be considered as part of an integrated surveillance system to support timely decision-making. [ABSTRACT FROM AUTHOR]

Background: Dengue is a vector-borne viral infection caused by the dengue virus transmitted to humans primarily by Aedes aegypti. The year 2024 has been a historic year for dengue in Brazil, with the highest number of probable cases ever registered. Herein, we analyze the temporal trend and spatio-temporal dynamics of dengue cases in Brazil during the first nine epidemiological weeks (EW) of 2024. Methods: This is an ecological study, including all probable cases of dengue in Brazil during the period, carried out in two steps: time series analysis to assess the temporal trend and spatial analysis to identify high-risk clusters. Results: 1,345,801 probable cases of dengue were reported. The regions with the highest increasing trend were the Northeast with an average epidemiologic week percent change (AEPC) of 52.4 (95% CI: 45.5–59.7; p < 0.001) and the South with 35.9 (95% CI: 27.7–44.5; p < 0.001). There was a statistically significant increasing trend in all states, except Acre (AEPC = -4.1; 95% CI: -16.3–10; p = 0.55), Amapá (AEPC = 1.3; 95% CI: -16.2–22.3; p = 0.9) and Espírito Santo (AEPC = 8.9; 95% CI: -15.7–40.6; p = 0.5). The retrospective space-time analysis showed a cluster within the Northeast, Central-West and Southeast regions, with a radius of 515.3 km, in which 1,267 municipalities and 525,324 of the cases were concentrated (RR = 6.3; p < 0.001). Regarding the spatial variation of the temporal trend, 21 risk areas were found, all of them located in Southeast or Central-West states. The area with the highest relative risk was Minas Gerais state, where 5,748 cases were concentrated (RR = 8.1; p < 0.001). Finally, a purely spatial analysis revealed 25 clusters, the one with the highest relative risk being composed of two municipalities in Acre (RR = 6.9; p < 0.001). Conclusions: We described a detailed temporal-spatial analysis of dengue cases in the first EWs of 2024 in Brazil, which were mainly concentrated in the Southeast and Central-West regions. Overall, it is recommended that governments adopt public policies to control the the vector population in high-risk areas, as well as to prevent the spread of dengue fever to other areas of Brazil. [ABSTRACT FROM AUTHOR]

Emerging infectious diseases are a major threat to biodiversity and an important public health issue. Flaviviruses are the cause of several emerging vector-borne zoonotic arboviruses whose distribution is currently increasing in Europe. The evidence that West Nile virus (WNV) circulates in resident and migratory species has implications for both animal and public health and should therefore be studied in depth. USUTU (USUV), Bagaza (BAGV) and tick-borne encephalitis virus (TBEV) are other viruses that are beginning to spread more widely. An integrated surveillance program, namely in birds, is essential for reducing the risk of infection in human populations within the One Health principles. In the present study, wild birds admitted to wildlife rehabilitation centers in Portugal were sampled. Two hundred eight blood samples were assayed serologically for antibodies to flaviviruses by using a commercial ELISA kit. An overall seroprevalence of 19.6% (95% confidence interval [CI]: 13.7–26.7%) was observed. Antibodies against flaviviruses were detected in 13 (35.1%) different species of wild birds. Accipitriformes (26.7%; 95% CI: 18.5–36.2%) and Strigiformes (26.7%; 95% CI: 14.6–42.0%) were the orders with the highest seroprevalence rates recorded. There were no statistically significant differences (p = 0.725) between the geographical regions (NUTS II) studied, but a statistically significant difference (p = 0.017) was found between sex (male: 34.4%; female: 4.8%). A higher seroprevalence was detected in adults (32.1%) than in juvenile birds (9.3%) (p = 0.014), and age was considered a risk factor for flavivirus infection in wild birds (odds ratio 1.4; 95% CI: 0.5–4.0). More epidemiological studies are needed in Portugal since the actual spread of the genus Flavivirus throughout the country is unknown. [ABSTRACT FROM AUTHOR]

More than 75 arboviruses are indigenous to Australia, of which at least 13 are known to cause disease in humans. Alphaviruses are the most common arboviruses, notably including Ross River and Barmah Forest viruses, which contribute a significant public health and economic burden in Australia. Both can cause febrile illness with arthritic symptoms. Each circulates nationally across diverse climates and environments, and has multi-host, multi-vector dynamics. Several medically important flaviviruses also circulate in Australia. Infection with Murray Valley encephalitis or Kunjin viruses is less common but is associated with brain inflammation. Key research priorities for Australian arboviruses aim to understand clinical manifestations, develop timely diagnostics, and identify transmission cycles that permit the maintenance of arboviruses. While these can now be answered for a handful of notifiable alpha- and flaviviruses there are others for which non-human vertebrate hosts and competent arthropod invertebrate vectors are still to be identified and/or whose role in transmission is not well understood. One or more of these 'neglected' arboviruses may be the causative agent of a proportion of the many thousands of fever-related illnesses reported annually in Australia that at present remain undiagnosed. Here, what is known about enzootic cycling of viruses between arthropod vectors and mammalian and avian reservoir hosts is summarised. How and to what extent these interactions influence the epidemiology of arbovirus transmission and infection is discussed. [ABSTRACT FROM AUTHOR]

Vector-borne diseases leave a large footprint on global health. Notable culprits include West Nile virus (WNV), St. Louis encephalitis virus (SLEV), and Japanese encephalitis virus (JEV), all transmitted by Culex mosquitoes. Chemical insecticides have been widely used to reduce the spread of mosquito-borne diseases. Still, mosquitoes are becoming more and more resistant to most chemical insecticides which cause particular harm to the ecology. Wolbachia belongs to the family Ehrlichiaceae in the order Rickettsiales and is a matrilineally inherited endosymbiont present in 60% of insects in nature. Wolbachia is capable of inducing a wide range of reproductive abnormalities in its hosts, such as cytoplasmic incompatibility, and can alter mosquito resistance to pathogen infection. Wolbachia has been proposed as a biological alternative to chemical vector control, and specific research progress and effectiveness have been achieved. Despite the importance of Wolbachia, this strategy has not been tested in Culex pipiens pallens, the most prevalent mosquito species in Shandong Province, China. Little is known about how the mass release of Wolbachia-infected mosquitoes may impact the genetic structure of Culex pipiens pallens, and how the symbiotic bacterium Wolbachia interacts with mitochondria during host mosquito transmission. Based on the population genetic structure of Culex pipiens pallens in Shandong Province, this study investigated the infection rate and infection type of Wolbachia in Shandong Province and jointly analysed the evolutionary relationship between the host mosquito and the symbiotic bacterium Wolbachia. Our study showed that Wolbachia naturally infected by Culex pipiens pallens in Shandong Province was less homologous to Wolbachia infected by Aedes albopictus released from mosquito factory in Guangzhou. Our results also show that Culex pipiens pallens is undergoing demographic expansion in Shandong Province. The overall Wolbachia infection rate of Culex pipiens pallens was 92.8%, and a total of 15 WSP haplotypes were detected. We found that the genetic diversity of Wolbachia was low in Culex pipiens pallens from Shandong Province, and the mosquitoes were infected only with type B Wolbachia. Visualizing the relationship between Culex pipiens pallens and Wolbachia using a tanglegram revealed patterns of widespread associations. A specific coevolutionary relationship exists between the host mosquito and Wolbachia. Knowledge of this mosquito–Wolbachia relationship will provide essential scientific information required for Wolbachia-based vector control approaches in Shandong Province and will lead to a better understanding of the diversity and evolution of Wolbachia for its utility as a biocontrol agent. Author summary: This study was the first to investigate the population genetic structure and Wolbachia infection of Culex pipiens pallens in Shandong Province, providing a basis for mosquito-borne control and disease prevention. The joint analysis of Wolbachia and mitochondrial markers highlighted the coevolutionary relationship between Wolbachia and its host. It also provided the scientific basis for green precision prevention and control of mosquito-borne bacteria and viruses. [ABSTRACT FROM AUTHOR]

Over the past decades, the number of arthropod-borne virus (arbovirus) outbreaks has increased worldwide. Knowledge regarding the sylvatic cycle (i.e., non-human hosts/environment) of arboviruses is limited, particularly in Africa, and the main hosts for virus maintenance are unknown. Previous studies have shown the presence of antibodies against certain arboviruses (i.e., chikungunya-, dengue-, and zika virus) in African non-human primates and bats. We hypothesize that small mammals, specifically rodents, may function as amplifying hosts in anthropogenic environments. The detection of RNA of most arboviruses is complicated by the viruses' short viremic period within their hosts. An alternative to determine arbovirus hosts is by detecting antibodies, which can persist several months. Therefore, we developed a high-throughput multiplex immunoassay to detect antibodies against 15 medically relevant arboviruses. We used this assay to assess approximately 1,300 blood samples of the multimammate mouse, Mastomys natalensis from Tanzania. In 24% of the samples, we detected antibodies against at least one of the tested arboviruses, with high seroprevalences of antibodies reacting against dengue virus serotype one (7.6%) and two (8.4%), and chikungunya virus (6%). Seroprevalence was higher in females and increased with age, which could be explained by inherent immunity and behavioral differences between sexes, and the increased chance of exposure to an arbovirus with age. We evaluated whether antibodies against multiple arboviruses co-occur more often than randomly and found that this may be true for some members of the Flaviviridae and Togaviridae. In conclusion, the development of an assay against a wide diversity of medically relevant arboviruses enabled the analysis of a large sample collection of one of the most abundant African small mammals. Our findings highlight that Mastomys natalensis is involved in the transmission cycle of multiple arboviruses and provide a solid foundation to better understand the role of this ubiquitous rodent in arbovirus outbreaks. Author summary: One of the main causes of zoonotic related human morbidity and mortality is the transmission of arthropod-borne viruses such as dengue virus, Yellow Fever virus, and chikungunya virus. These viruses cannot only infect humans but also livestock, pets, and wildlife, though our understanding of their non-human hosts remains limited. Rodents are thought to be an important host for these viruses because they can be abundant, often live near humans, and some are already known to be viral hosts. However, research has focused mostly on non-human primates, neglecting other potential wild hosts. To address this gap, we have developed a high-throughput antibody test to screen rodent blood against 15 different arboviruses. Our findings reveal that Mastomys natalensis, a common African rodent species, carries antibodies that (cross-)react against these viruses. We hypothesize that immunologically naïve juveniles may drive transmission, particularly during population outbreaks. These outbreaks coincide with environmental conditions that are favorable for mosquitoes, thus increasing the risk of spillover to humans, livestock, and wildlife. Understanding the role of rodents in arbovirus transmission dynamics is crucial for mitigating zoonotic disease risks. [ABSTRACT FROM AUTHOR]

Introduction: Armenia's favorable geographical and climatic conditions support mosquitoes, sandflies, and ticks that can transmit various diseases. This study aimed to determine the prevalence of these vectors and circulating arboviruses in Armenia and assess healthcare workers' knowledge of arboviral diseases. Methodology: In 2021, we conducted fieldwork, combining morphological identification of vectors with polymerase chain reaction (PCR) analysis of pathogens to map the distribution of potential arbovirus vectors across Armenia. Results: Our entomological surveys identified four mosquito genera--Anopheles, Aedes, Culex, and Culiseta--comprising 20 species; and 11 species of Ixodidae ticks. Culex pipiens was found in all 11 regions, while Culiseta spp. was absent in Ararat Province. PCR testing of mosquito and tick samples revealed Crimean-Congo hemorrhagic fever virus (CCHFV) in 13 tick samples, but West Nile virus (WNV) was not detected in mosquitoes. Specifically, 13 out of 525 Ixodes tick pools tested positive for CCHFV; the positive samples originated from Hyalomma marginatum ticks in Syunik's Sisian region. None of the 11 pools that contained 473 Cx. pipiens mosquitoes tested positive for WNV. Analysis of questionnaires from 499 healthcare workers showed that epidemiologists, infectious disease specialists, and family doctors had greater awareness of arboviral diseases than other specialists. However, there was a low rate of sample submission for laboratory diagnosis and confirmation. Conclusions: The extensive presence of vectors combined with limited knowledge of arboviral diseases complicates disease understanding in Armenia. Strengthening the surveillance system through training and improved sample collection is essential for disease monitoring and public health interventions. [ABSTRACT FROM AUTHOR]

Background and Objectives: In Brazil, urban arboviruses, such as dengue virus (DENV), Zika virus (ZIKV) and chikungunya virus (CHIKV), constitute a major public health problem, and due to their endemicity and asymptomatic cases, they pose a potential threat to blood donations. Rio de Janeiro (RJ), Brazil, has been impacted by extensive DENV epidemics over the last 30 years and, after 2015, by CHIKV and ZIKV. Materials and Methods: Urban arboviruses DENV, ZIKV and CHIKV were investigated in blood donations (n = 778) at the State Institute of Hematology, HEMORIO (RJ) from 2019 to 2022 by serological and molecular methods. Results: An overall arbovirus exposure was observed in 26.1% of the blood donations. Anti‐DENV IgM was detected in 4.0% of samples and two donations were DENV NS1 positive. Positive anti‐CHIKV IgM was observed in 4.7% of the donations. Co‐detection of anti‐CHIKV IgM and anti‐DENV IgM was observed in 1.0% of donors, and CHIKV prevalence was 21.3%. All blood donations tested were negative for the DENV, ZIKV and CHIKV RNA. Conclusion: IgM seroprevalence to the arboviruses analyzed here is an indicator of recent infection in asymptomatic donors, showing that the population of blood donors can be a vehicle for new infections, especially during epidemic periods. [ABSTRACT FROM AUTHOR]

Diseases transmitted by arthropod-borne viruses such as West Nile virus (WNV) and chikungunya virus (CHIKV) pose threat to global public health. Unfortunately, to date, there is no available approved drug for severe symptoms caused by both viruses. It has been reported that reverse transcriptase inhibitors can effectively inhibit RNA polymerase activity of RNA viruses. We screened the anti-WNV activity of the FDA-approved reverse transcriptase inhibitor library and found that 4 out of 27 compounds showed significant antiviral activity. Among the candidates, etravirine markedly inhibited WNV infection in both Huh 7 and SH-SY5Y cells. Further assays revealed that etravirine inhibited the infection of multiple arboviruses, including yellow fever virus (YFV), tick-borne encephalitis virus (TBEV), and CHIKV. A deeper study at the phase of action showed that the drug works primarily during the viral replication process. This was supported by the strong interaction potential between etravirine and the RNA-dependent RNA polymerase (RdRp) of WNV and alphaviruses, as evaluated using molecular docking. In vivo, etravirine significantly rescued mice from WNV infection-induced weight loss, severe neurological symptoms, and death, as well as reduced the viral load and inflammatory cytokines in target tissues. Etravirine showed antiviral effects in both arthrophlogosis and lethal mouse models of CHIKV infection. This study revealed that etravirine is an effective anti-WNV and CHIKV arbovirus agent both in vitro and in vivo due to the inhibition of viral replication, providing promising candidates for clinical application. [ABSTRACT FROM AUTHOR]

Insect-specific viruses (ISVs) include viruses that are restricted to the infection of mosquitoes and are spread mostly through transovarial transmission. Despite using a distinct mode of transmission, ISVs are often phylogenetically related to arthropod-borne viruses (arboviruses) that are responsible for human diseases and able to infect both mosquitoes and vertebrates. ISVs can also induce a phenomenon called "superinfection exclusion", whereby a primary ISV infection in an insect inhibits subsequent viral infections of the insect. This has sparked interest in the use of ISVs for the control of pathogenic arboviruses transmitted by mosquitoes. In particular, insect-specific flaviviruses (ISFs) have been shown to inhibit infection of vertebrate-infecting flaviviruses (VIFs) both in vitro and in vivo. This has shown potential as a new and ecologically friendly biological approach to the control of arboviral disease. For this intervention to have lasting impacts for biological control, it is imperative that ISFs are maintained in mosquito populations with high rates of vertical transmission. Therefore, these strategies will need to optimise vertical transmission of ISFs in order to establish persistently infected mosquito lines for sustainable arbovirus control. This review compares recent observations of vertical transmission of arboviral and insect-specific flaviviruses and potential determinants of transovarial transmission rates to understand how the vertical transmission of ISFs may be optimised for effective arboviral control. [ABSTRACT FROM AUTHOR]

Simple Summary: Several literature reviews of arboviruses in Nigeria have demonstrated a high prevalence of chikungunya and dengue antibodies in individuals with either febrile or non-febrile illness. The current study reveals a substantial burden of undetected arboviral cocirculating antibodies of these mosquito-borne diseases in the country. This underscores the importance of incorporating multiplex diagnostic testing and surveillance efforts to accurately determine the full extent of the arbovirus disease burden in Nigeria and Sub-Saharan Africa. Chikungunya and dengue are arboviral diseases transmitted by mosquitoes that have been increasingly recognized as public health concerns in Sub-Saharan Africa. Several studies conducted in Nigeria and other West African countries have revealed the seroprevalence burden and cocirculation of antibodies against mosquito-borne infections, thereby revealing a significant burden and clinical outcome complexities that have largely gone undetected. The current research study has important implications for disease surveillance, prevention strategies, and healthcare planning in Nigeria and other Sub-Saharan countries. A cross-sectional study was conducted on 871 outpatients and pregnant women from three regions of Nigeria. CHIKV and DENV immunoblot molecular diagnostic assays were used to analyze the serum samples for the presence of arboviral antibody serological markers IgG (Mikrogen Diagnostik, Germany) with DENV nonstructural protein 1 and DENV Equad and CHIKV virus-like particles (VLPs), according to the manufacturer's instructions. A total of 871 participants were recruited from three geographical regions in Nigeria. Among them, 17.5% (152/871) were from Abia (southern Nigeria), 34.4% (300/871) were from Kaduna (northern Nigeria), and 48.1% (419/871) were from Nasarawa (central Nigeria). The ages of the participants ranged from 0 months to 80 years, with a mean age of 36.6 years. Of the 871 subjects, 71.0% (619/871) were female, and 29.0% (252/871) were male. The overall cohort detectable antibody seropositivity against CHIKV was 64.9% (565/871), 95% CI (61.74–68.06); DENV, 44.7% (389/871), 95% CI (41.41–47.99); and CHIKV-DENV cocirculation antibodies, 31.6% (95% CI 29–35). This study highlighted the unpredictably high seroprevalence, expansion, magnitude, and undetected burden of chikungunya and dengue in Nigeria. [ABSTRACT FROM AUTHOR]

Background and Objectives: The steady spread of dengue virus (DENV) poses a profound public health threat worldwide. Reverse transcription real-time polymerase chain reaction (RT2-PCR) has been increasingly recognized as a reference method for the diagnosis of acute dengue infection. The goal of this study was to assess the diagnostic accuracy of five different RT2-PCR kits for the detection of DENV in a historically processed set of sera samples. Materials and Methods: In this retrospective study, 25 sera samples from routinely processed unique adult patients with a known DENV status (previously tested in both molecular and serological assays) were tested in parallel using four conventional (RealStar Dengue PCR Kit 3.0, Clonit'ngo Zika, Dengue & Chikungunya, BioPerfectus Zika Virus/Dengue Virus/Chikungunya Virus Real Time PCR Kit and Novaplex Tropical fever virus) and one sample-to-result (STANDARD M10 Arbovirus Panel) RT2-PCR assays. Additionally, an end-point dilution analysis was conducted in quintuplicate on six serial dilutions of an RNA preparation obtained from a culture-grown DENV serotype 1 strain for a total of 150 tests. Results: The overall accuracy of the evaluated tests ranged from 84% to 100%. In particular, the sensitivity of three conventional RT2-PCR assays (RealStar, Clonit'ngo and Novaplex) was 100% (95% CI: 79.6–100%), while it was lower (73.3%; 95% CI: 48.1–89.1%) for the BioPerfectus kit. The sample-to-result STANDARD M10 panel performed comparatively well, showing a sensitivity of 92.9% (95% CI: 68.5–98.7%). No false positive results were registered in any assay. The end-point dilution analysis suggested that the RealStar kit had the lowest limit of detection. Conclusions: Available RT2-PCR kits for the detection of DENV are highly specific and generally sensitive and, therefore, their implementation in diagnostic pathways is advisable. [ABSTRACT FROM AUTHOR]

Among the main arboviruses affecting public health in tropical regions are dengue, zika, and chikungunya, transmitted mainly by mosquitoes of the Aedes genus, especially Aedes aegypti. In recent years, outbreaks have posed major challenges to global health, highlighting the need for integrated and innovative strategies for their control and prevention. Prevention strategies include the elimination of vectors and avoiding mosquito bites; this can be achieved through the use of bioinsecticides and repellents based on plant phytochemicals, as they offer sustainable, ecological, and low-cost alternatives. Mexico has a variety of plants from which both extracts and essential oils have been obtained which have demonstrated significant efficacy in repelling and/or killing insect vectors. This review examines the current knowledge on plant species found in Mexico which are promising options concerning synthetic compounds in terms of their repellent and insecticidal properties against mosquitoes of the genus Aedes and that are friendly to the environment and health. [ABSTRACT FROM AUTHOR]

Phylogenetic analyses showed that the virus responsible for a May 2024 Oropouche fever outbreak in Cuba was closely related to viruses from Brazil in 2023. Pools of Ceratopogonidae spp. biting midges and Culex quinquefasciatus mosquitoes were positive for Oropouche viral RNA. No cases were severe. Virus extension to new areas may increase case numbers and severity.

Abstract Background Dengue is a vector-borne viral infection caused by the dengue virus transmitted to humans primarily by Aedes aegypti. The year 2024 has been a historic year for dengue in Brazil, with the highest number of probable cases ever registered. Herein, we analyze the temporal trend and spatio-temporal dynamics of dengue cases in Brazil during the first nine epidemiological weeks (EW) of 2024. Methods This is an ecological study, including all probable cases of dengue in Brazil during the period, carried out in two steps: time series analysis to assess the temporal trend and spatial analysis to identify high-risk clusters. Results 1,345,801 probable cases of dengue were reported. The regions with the highest increasing trend were the Northeast with an average epidemiologic week percent change (AEPC) of 52.4 (95% CI: 45.5–59.7; p

Abstract Background The effectiveness of dengue control interventions depends on an effective integrated surveillance system that involves analysis of multiple variables associated with the natural history and transmission dynamics of this arbovirus. Entomological indicators associated with other biotic and abiotic parameters can assertively characterize the spatiotemporal trends related to dengue transmission risk. However, the unpredictability of the non-linear nature of the data, as well as the uncertainty and subjectivity inherent in biological data are often neglected in conventional models. Methods As an alternative for analyzing dengue-related data, we devised a fuzzy-logic approach to test ensembles of these indicators across categories, which align with the concept of degrees of truth to characterize the success of dengue transmission by Aedes aegypti mosquitoes in an endemic city in Brazil. We used locally gathered entomological, demographic, environmental and epidemiological data as input sources using freely available data on digital platforms. The outcome variable, risk of transmission, was aggregated into three categories: low, medium, and high. Spatial data was georeferenced and the defuzzified values were interpolated to create a map, translating our findings to local public health managers and decision-makers to direct further vector control interventions. Results The classification of low, medium, and high transmission risk areas followed a seasonal trend expected for dengue occurrence in the region. The fuzzy approach captured the 2020 outbreak, when only 14.06% of the areas were classified as low risk. The classification of transmission risk based on the fuzzy system revealed effective in predicting an increase in dengue transmission, since more than 75% of high-risk areas had an increase in dengue incidence within the following 15 days. Conclusions Our study demonstrated the ability of fuzzy logic to characterize the city’s spatiotemporal heterogeneity in relation to areas at high risk of dengue transmission, suggesting it can be considered as part of an integrated surveillance system to support timely decision-making.

We assessed the spatiotemporal dynamics of Oropouche fever in Brazil during 2015–2024. We found the number of cases substantially increased during that period, particularly in the Amazon region. Our findings underscore the need for improved surveillance and public health measures in response to the disease’s potential spread beyond endemic areas.

Chikungunya and dengue are arboviral diseases transmitted by mosquitoes that have been increasingly recognized as public health concerns in Sub-Saharan Africa. Several studies conducted in Nigeria and other West African countries have revealed the seroprevalence burden and cocirculation of antibodies against mosquito-borne infections, thereby revealing a significant burden and clinical outcome complexities that have largely gone undetected. The current research study has important implications for disease surveillance, prevention strategies, and healthcare planning in Nigeria and other Sub-Saharan countries. A cross-sectional study was conducted on 871 outpatients and pregnant women from three regions of Nigeria. CHIKV and DENV immunoblot molecular diagnostic assays were used to analyze the serum samples for the presence of arboviral antibody serological markers IgG (Mikrogen Diagnostik, Germany) with DENV nonstructural protein 1 and DENV Equad and CHIKV virus-like particles (VLPs), according to the manufacturer’s instructions. A total of 871 participants were recruited from three geographical regions in Nigeria. Among them, 17.5% (152/871) were from Abia (southern Nigeria), 34.4% (300/871) were from Kaduna (northern Nigeria), and 48.1% (419/871) were from Nasarawa (central Nigeria). The ages of the participants ranged from 0 months to 80 years, with a mean age of 36.6 years. Of the 871 subjects, 71.0% (619/871) were female, and 29.0% (252/871) were male. The overall cohort detectable antibody seropositivity against CHIKV was 64.9% (565/871), 95% CI (61.74–68.06); DENV, 44.7% (389/871), 95% CI (41.41–47.99); and CHIKV-DENV cocirculation antibodies, 31.6% (95% CI 29–35). This study highlighted the unpredictably high seroprevalence, expansion, magnitude, and undetected burden of chikungunya and dengue in Nigeria.

Abstract Background To assess whether the ‘economic boom’ in the tropical seaport city of Barranquilla improved tapped water supplies to socio-economically poor neighbourhoods resulting in: (1) their reduced use for domestic water-storage in large (> 1,000-litre) custom-made cement tanks which are their principal Aedes aegypti breeding sites and (2) their pupae/person index (PPI) values to below their established 0.5–1.5 PPI arbovirus transmission-threshold value, compared to matched neighbourhoods in the: (a) pre-economic boom (2004) period in Barranquilla and (b) economically-neglected seaport city of Buenaventura. Methods The simple, accurate and robust water surface sweep-net/calibration factor or total count methods were used to determine the total Ae. aegypti pupae numbers in greater or less than 20-litre water-holding container types located ‘inside’ or ‘outside’ these neighbourhood premises. The women residents also participated in questionnaire-based responses about their domestic water supplies, water-storage and maintenance and mosquito life stages and disease transmission knowledge, to subsequently plan appropriate resident education programmes. Microsoft Excel 8.0 with OpenEpi was used to determine the samples sizes and the statistical values. Results Tapped water supplies to the three poor Barranquilla neighbourhoods were dramatically increased from 2004 to 2023 resulting in their residents significantly reducing their: (a) large cement water-storage tanks from 1 per 6.9 (2004) to 1 per 31.2 (2020) premises (z = 10.5: p = 0) and (b) PPI values to 0.16, 0.19 and 0.53 (mean: 0.29: 95% CI ± 0.4) in each study neighbourhood. In contrast, tapped water supplies remained inadequate in the Buenaventura neighborhoods, thereby resulting in their continued use of many large (> 1,000-litre) water-storage containers (Barranquilla: 1 per 31.2 and Buenaventura: 1 per 1.5 premises: z = − 9.26: p = 0), with unacceptably high 0.81, 0.88 and 0.99 PPI values in each study neighbourhood (mean 0.89: 95% CI ± 0.12). Conclusions Improved tapped water supplies resulted in reduced numbers of large custom-made stoneware water-containers, as are employed by poor residents throughout the world, as well as their Ae. aegypti PPI transmission threshold values which, together with appropriate residents’ education programmes, are also urgently to reduce to prevent/reduce Ae. aegypti transmitted human diseases globally.

Little is known about using noninvasive samples for diagnosing Crimean-Congo hemorrhagic fever (CCHF). We investigated detection of CCHF virus in serum, saliva, and urine samples. Our results indicate that serum is the best sample type for CCHF diagnosis; saliva can be used for noninvasive sampling.

Dengue fever (DF) is the most frequent arboviral disease globally. Deforestation, armed conflicts, and climate change have caused an unprecedented global spread of DF, raising concerns in healthcare systems worldwide. Systemic manifestations of the disease range from mild to severe and, in some cases, can lead to death. Although neurological complications have been reported over the last few decades, they are often neglected or underreported. The present narrative review aims to describe the most important central and peripheral nervous system complications and provide guidance to neurologists in terms of diagnosis and management.

Abstract Dengue causes approximately 10.000 deaths and 100 million symptomatic infections annually worldwide, making it a significant public health concern. To address this, artificial intelligence tools like machine learning can play a crucial role in developing more effective strategies for control, diagnosis, and treatment. This study identifies relevant variables for the screening of dengue cases through machine learning models and evaluates the accuracy of the models. Data from reported dengue cases in the states of Rio de Janeiro and Minas Gerais for the years 2016 and 2019 were obtained through the National Notifiable Diseases Surveillance System (SINAN). The mutual information technique was used to assess which variables were most related to laboratory-confirmed dengue cases. Next, a random selection of 10,000 confirmed cases and 10,000 discarded cases was performed, and the dataset was divided into training (70%) and testing (30%). Machine learning models were then tested to classify the cases. It was found that the logistic regression model with 10 variables (gender, age, fever, myalgia, headache, vomiting, nausea, back pain, rash, retro-orbital pain) and the Decision Tree and Multilayer Perceptron (MLP) models achieved the best results in decision metrics, with an accuracy of 98%. Therefore, a tree-based model would be suitable for building an application and implementing it on smartphones. This resource would be available to healthcare professionals such as doctors and nurses.

Background: Mosquito host feeding patterns are an important factor of the species-specific vector capacity determining pathogen transmission routes. Culex pipiens s.s./Cx. torrentium are competent vectors of several arboviruses, such as West Nile virus and Usutu virus. However, studies on host feeding patterns rarely differentiate the morphologically indistinguishable females. Methods: We analyzed the host feeding attraction of Cx. pipiens and Cx. torrentium in host-choice studies for bird, mouse, and a human lure. In addition, we summarized published and unpublished data on host feeding patterns of field-collected specimens from Germany, Iran, and Moldova from 2012 to 2022, genetically identified as Cx. pipiens biotype pipiens, Cx. pipiens biotype molestus, Cx. pipiens hybrid biotype pipiens × molestus, and Cx. torrentium, and finally put the data in context with similar data found in a systematic literature search. Results: In the host-choice experiments, we did not find a significant attraction to bird, mouse, and human lure for Cx. pipiens pipiens and Cx. torrentium. Hosts of 992 field-collected specimens were identified for Germany, Iran, and Moldova, with the majority determined as Cx. pipiens pipiens, increasing the data available from studies known from the literature by two-thirds. All four Culex pipiens s.s./Cx. torrentium taxa had fed with significant proportions on birds, humans, and nonhuman mammals. Merged with the data from the literature from 23 different studies showing a high prevalence of blood meals from birds, more than 50% of the blood meals of Cx. pipiens s.s. were identified as birds, while up to 39% were human and nonhuman mammalian hosts. Culex torrentium fed half on birds and half on mammals. However, there were considerable geographical differences in the host feeding patterns. Conclusions: In the light of these results, the clear characterization of the Cx. pipiens s.s./Cx. torrentium taxa as ornithophilic/-phagic or mammalophilic/-phagic needs to be reconsidered. Given their broad host ranges, all four Culex taxa could potentially serve as enzootic and bridge vectors. [ABSTRACT FROM AUTHOR]

Usutu (USUV), West Nile (WNV), and Zika virus (ZIKV) are neurotropic arthropod-borne viruses (arboviruses) that cause severe neurological disease in humans. However, USUV-associated neurological disease is rare, suggesting a block in entry to or infection of the brain. We determined the replication, cell tropism and neurovirulence of these arboviruses in human brain tissue using a well-characterized human fetal organotypic brain slice culture model. Furthermore, we assessed the efficacy of interferon-β and 2′C-methyl-cytidine, a synthetic nucleoside analogue, in restricting viral replication. All three arboviruses replicated within the brain slices, with WNV reaching the highest titers, and all primarily infected neuronal cells. USUV- and WNV-infected cells exhibited a shrunken morphology, not associated with detectable cell death. Pre-treatment with interferon-β inhibited replication of all arboviruses, while 2′C-methyl-cytidine reduced only USUV and ZIKV titers. Collectively, USUV can infect human brain tissue, showing similarities in tropism and neurovirulence as WNV and ZIKV. These data suggest that a blockade to infection of the human brain may not be the explanation for the low clinical incidence of USUV-associated neurological disease. However, USUV replicated more slowly and to lower titers than WNV, which could help to explain the reduced severity of neurological disease resulting from USUV infection. [ABSTRACT FROM AUTHOR]

The family Borreliaceae contains arthropod-borne spirochetes that cause two widespread human diseases, Lyme disease and relapsing fever. Lyme disease is a subacute, progressive illness with variable stage and tissue manifestations. Relapsing fever is an acute febrile illness with prominent bacteremia that may recur and disseminate, particularly to the nervous system. Clinical heterogeneity is a hallmark of both diseases. While human clinical manifestations are influenced by a wide variety of factors, including immune status and host genetic susceptibility, there is evidence that Borreliaceae microbial factors influence the clinical manifestations of human disease caused by this family of spirochetes. Despite these associations, the spirochete genes that influence the severity and manifestations of human disease are, for the most part, unknown. Recent work has identified lineage-specific expansions of lipoproteome-rich accessory genome elements in virulent clones of Borrelia burgdorferi. Using publicly available genome assemblies, it is shown that all Borreliaceae lineages for which sufficient sequence data are available harbor a similar pattern of strongly structured, lineage-specific expansions in their accessory genomes, particularly among lipoproteins, and that this pattern holds across phylogenetic scales including genera, species, and genotypes. The relationships among pangenome elements suggest that infrequent episodes of marked genomic change followed by clonal expansion in geographically and enzootically structured populations may account for the unique lineage structure of Borreliaceae. This analysis informs future genotype–phenotype studies among Borreliaceae and lays a foundation for studies of individual gene function guided by phylogenetic patterns of conservation, diversification, gain, and/or loss. [ABSTRACT FROM AUTHOR]

Wolbachia symbionts introduced into Aedes mosquitoes provide a highly effective dengue virus transmission control strategy, increasingly utilised in many countries in an attempt to reduce disease burden. Whilst highly effective against dengue and other positive-sense RNA viruses, it remains unclear how effective Wolbachia is against negative-sense RNA viruses. Therefore, the effect of Wolbachia on Bunyamwera virus (BUNV) infection in Aedes aegypti was investigated using wMel and wAlbB, two strains currently used in Wolbachia releases for dengue control, as well as wAu, a strain that typically persists at a high density and is an extremely efficient blocker of positive-sense viruses. Wolbachia was found to reduce BUNV infection in vitro but not in vivo. Instead, BUNV caused significant impacts on density of all three Wolbachia strains following infection of Ae. aegypti mosquitoes. The ability of Wolbachia to successfully persist within the mosquito and block virus transmission is partially dependent on its intracellular density. However, reduction in Wolbachia density was not observed in offspring of infected mothers. This could be due in part to a lack of transovarial transmission of BUNV observed. The results highlight the importance of understanding the complex interactions between multiple arboviruses, mosquitoes and Wolbachia in natural environments, the impact this can have on maintaining protection against diseases, and the necessity for monitoring Wolbachia prevalence at release sites. [ABSTRACT FROM AUTHOR]

Chikungunya virus (CHIKV) is a reemerging arbovirus causing disease on a global scale, and the potential for its epidemics remains high. CHIKV has caused millions of cases and heavy economic burdens around the world, while there are no available approved antiviral therapies to date. In this study, nifuroxazide, an FDA-approved antibiotic for acute diarrhea or colitis, was found to significantly inhibit a variety of arboviruses, although its antiviral activity varied among different target cell types. Nifuroxazide exhibited relatively high inhibitory efficiency in yellow fever virus (YFV) infection of the hepatoma cell line Huh7, tick-borne encephalitis virus (TBEV) and west nile virus (WNV) infection of the vascular endothelial cell line HUVEC, and CHIKV infection of both Huh7 cells and HUVECs, while it barely affected the viral invasion of neurons. Further systematic studies on the action stage of nifuroxazide showed that nifuroxazide mainly inhibited in the viral replication stage. In vivo, nifuroxazide significantly reduced the viral load in muscles and protected mice from CHIKV-induced footpad swelling, an inflammation injury within the arthrosis of infected mice. These results suggest that nifuroxazide has a potential clinical application as an antiviral drug, such as in the treatment of CHIKV infection. [ABSTRACT FROM AUTHOR]

French Guiana experienced an unprecedented dengue epidemic during 2023–2024. Prior to the 2023–2024 outbreak in French Guiana, DENV-3 had not circulated in an epidemic manner since 2005. We therefore studied retrospectively the strains circulating in the French Territories of the Americas (FTA)—French Guiana, Guadeloupe, and Martinique—from the 2000s to the current epidemic. To this end, DENV-3 samples from the collection of the National Reference Center for Arboviruses in French Guiana (NRCA-FG) were selected and sequenced using next-generation sequencing (NGS) based on Oxford Nanopore Technologies, ONT. Phylogenetic analysis showed that (i) the 97 FTA sequences obtained all belonged to genotype III (GIII); (ii) between the 2000s and 2013, the regional circulation of the GIII American-I lineage was the source of the FTA cases through local extinctions and re-introductions; (iii) multiple introductions of lineages of Asian origin appear to be the source of the 2019–2021 epidemic in Martinique and the 2023–2024 epidemic in French Guiana. Genomic surveillance is a key factor in identifying circulating DENV genotypes, monitoring strain evolution, and identifying import events. [ABSTRACT FROM AUTHOR]

In July 2017, a family of three members, a 46-year-old male, a 45-year-old female and their 8-year-old daughter, returned to South Africa from Thailand. They presented symptoms consistent with mosquito-borne diseases, including fever, headache, severe body aches and nausea. Mosquito bites in all family members suggested recent exposure to arthropod-borne viruses. Dengue virus 1 (Genus Orthoflavivirus) was isolated (isolate no. SA397) from the serum of the 45-year-old female via intracerebral injection in neonatal mice and subsequent passage in VeroE6 cells. Phylogenetic analysis of this strain indicated close genetic identity with cosmopolitan genotype 1 DENV1 strains from Southeast Asia, assigned to major lineage K, minor lineage 1 (DENV1I_K.1), such as GZ8H (99.92%) collected in November 2018 from China, and DV1I-TM19-74 isolate (99.72%) identified in Bangkok, Thailand, in 2019. Serum samples from the 46-year-old male yielded a virus isolate that could not be confirmed as DENV1, prompting unbiased metagenomic sequencing for virus identification and characterization. Illumina sequencing identified multiple segments of a mammalian orthoreovirus (MRV), designated as Human/SA395/SA/2017. Genomic and phylogenetic analyses classified Human/SA395/SA/2017 as MRV-3 and assigned a tentative genotype, MRV-3d, based on the S1 segment. Genomic analyses suggested that Human/SA395/SA/2017 may have originated from reassortments of segments among swine, bat, and human MRVs. The closest identity of the viral attachment protein σ1 (S1) was related to a human isolate identified from Tahiti, French Polynesia, in 1960. This indicates ongoing circulation and co-circulation of Southeast Asian and Polynesian strains, but detailed knowledge is hampered by the limited availability of genomic surveillance. This case represents the rare concurrent detection of two distinct viruses with different transmission routes in the same family with similar clinical presentations. It highlights the complexity of diagnosing diseases with similar sequelae in travelers returning from tropical areas. [ABSTRACT FROM AUTHOR]

Flaviviruses comprise a large number of arthropod-borne viruses, some of which are associated with life-threatening diseases. Flavivirus infections are rising worldwide, mainly due to the proliferation and geographical expansion of their vectors. The main human pathogens are mosquito-borne flaviviruses, including dengue virus, Zika virus, and West Nile virus, but tick-borne flaviviruses are also emerging. As with any viral infection, the body's first line of defense against flavivirus infections is the innate immune defense, of which type I interferon is the armed wing. This cytokine exerts its antiviral activity by triggering the synthesis of hundreds of interferon-induced genes (ISGs), whose products can prevent infection. Among the ISGs that inhibit flavivirus replication, certain tripartite motif (TRIM) proteins have been identified. Although involved in other biological processes, TRIMs constitute a large family of antiviral proteins active on a wide range of viruses. Furthermore, whereas some TRIM proteins directly block viral replication, others are positive regulators of the IFN response. Therefore, viruses have developed strategies to evade or counteract TRIM proteins, and some even hijack certain TRIM proteins to their advantage. In this review, we summarize the current state of knowledge on the interactions between flaviviruses and TRIM proteins, covering both direct and indirect antiviral mechanisms. [ABSTRACT FROM AUTHOR]

The most prevalent arthropod-borne viruses, including the dengue viruses, are primarily transmitted by infected mosquitoes. However, the dynamics of dengue virus (DENV) infection and dissemination in human skin following Aedes aegypti probing remain poorly understood. We exposed human skin explants to adult female Ae. aegypti mosquitoes following their infection with DENV-2 by intrathoracic injection. Skin explants inoculated with a similar quantity of DENV-2 by a bifurcated needle were used as controls. Quantitative in situ imaging revealed that DENV replication was greatest in keratinocytes in the base of the epidermis, accounting for 50–60% of all infected cells regardless of the route of inoculation. However, DENV inoculation by Ae. aegypti probing resulted in an earlier and increased viral replication in the dermis, infecting twice as many cells at 24 h when compared to needle inoculation. Within the dermis, enhanced replication of DENV by Ae. aegypti infected mosquitoes was mediated by increased local recruitment of skin-resident macrophages, dermal dendritic cells, and epidermal Langerhans cells relative to needle inoculation. An enhanced but less pronounced influx of resident myeloid cells to the site of mosquito probing was also observed in the absence of infection. Ae. aegypti probing also increased recruitment and infection of dermal mast cells. Our findings reveal for the first time that keratinocytes are the primary targets of DENV infection following Ae. aegypti inoculation, even though most of the virus is inoculated into the dermis during probing. The data also show that mosquito probing promotes the local recruitment and infection of skin-resident myeloid cells in the absence of an intact vasculature, indicating that influx of blood-derived neutrophils is not an essential requirement for DENV spread within and out of skin. [ABSTRACT FROM AUTHOR]

The emergence and re-emergence of arthropod-borne viruses is a public health threat. For routine surveillance in public health laboratories, cost-effective and reproducible methods are essential. In this review, we address the technical considerations of high-throughput sequencing methods (HTS) for arbovirus surveillance in national health laboratories, focusing on pre-sequencing, sequencing, and post-sequencing approaches, underlining the importance of robust wet and dry laboratory workflows for reproducible analysis. We aim to provide insights for researchers and clinicians interested in arbovirus, diagnosis, and surveillance by discussing current advances in sequencing methods and bioinformatics pipelines applied to arboviruses. [ABSTRACT FROM AUTHOR]

Background: To assess whether the 'economic boom' in the tropical seaport city of Barranquilla improved tapped water supplies to socio-economically poor neighbourhoods resulting in: (1) their reduced use for domestic water-storage in large (> 1,000-litre) custom-made cement tanks which are their principal Aedes aegypti breeding sites and (2) their pupae/person index (PPI) values to below their established 0.5–1.5 PPI arbovirus transmission-threshold value, compared to matched neighbourhoods in the: (a) pre-economic boom (2004) period in Barranquilla and (b) economically-neglected seaport city of Buenaventura. Methods: The simple, accurate and robust water surface sweep-net/calibration factor or total count methods were used to determine the total Ae. aegypti pupae numbers in greater or less than 20-litre water-holding container types located 'inside' or 'outside' these neighbourhood premises. The women residents also participated in questionnaire-based responses about their domestic water supplies, water-storage and maintenance and mosquito life stages and disease transmission knowledge, to subsequently plan appropriate resident education programmes. Microsoft Excel 8.0 with OpenEpi was used to determine the samples sizes and the statistical values. Results: Tapped water supplies to the three poor Barranquilla neighbourhoods were dramatically increased from 2004 to 2023 resulting in their residents significantly reducing their: (a) large cement water-storage tanks from 1 per 6.9 (2004) to 1 per 31.2 (2020) premises (z = 10.5: p = 0) and (b) PPI values to 0.16, 0.19 and 0.53 (mean: 0.29: 95% CI ± 0.4) in each study neighbourhood. In contrast, tapped water supplies remained inadequate in the Buenaventura neighborhoods, thereby resulting in their continued use of many large (> 1,000-litre) water-storage containers (Barranquilla: 1 per 31.2 and Buenaventura: 1 per 1.5 premises: z = − 9.26: p = 0), with unacceptably high 0.81, 0.88 and 0.99 PPI values in each study neighbourhood (mean 0.89: 95% CI ± 0.12). Conclusions: Improved tapped water supplies resulted in reduced numbers of large custom-made stoneware water-containers, as are employed by poor residents throughout the world, as well as their Ae. aegypti PPI transmission threshold values which, together with appropriate residents' education programmes, are also urgently to reduce to prevent/reduce Ae. aegypti transmitted human diseases globally. [ABSTRACT FROM AUTHOR]