Mosquito saliva enhances virus infection through sialokinin-dependent vascular leakage.

Viruses transmitted by Aedes mosquitoes are an increasingly important global cause of disease. Defining common determinants of host susceptibility to this large group of heterogenous pathogens is key for informing the rational design of panviral medicines. Infection of the vertebrate host with these viruses is enhanced by mosquito saliva, a complex mixture of salivary-gland-derived factors and microbiota. We show that the enhancement of infection by saliva was dependent on vascular function and was independent of most antisaliva immune responses, including salivary microbiota. Instead, the Aedes gene product sialokinin mediated the enhancement of virus infection through a rapid reduction in endothelial barrier integrity. Sialokinin is unique within the insect world as having a vertebrate-like tachykinin sequence and is absent from Anopheles mosquitoes, which are incompetent for most arthropod-borne viruses, whose saliva was not proviral and did not induce similar vascular permeability. Therapeutic strategies targeting sialokinin have the potential to limit disease severity following infection with Aedes-mosquito-borne viruses.

Alpha-mannosidase-2 modulates arbovirus infection in a pathogen- and Wolbachia-specific manner in Aedes aegypti mosquitoes.

Multiple Wolbachia strains can block pathogen infection, replication and/or transmission in Aedes aegypti mosquitoes under both laboratory and field conditions. However, Wolbachia effects on pathogens can be highly variable across systems and the factors governing this variability are not well understood. It is increasingly clear that the mosquito host is not a passive player in which Wolbachia governs pathogen transmission phenotypes; rather, the genetics of the host can significantly modulate Wolbachia-mediated pathogen blocking. Specifically, previous work linked variation in Wolbachia pathogen blocking to polymorphisms in the mosquito alpha-mannosidase-2 (αMan2) gene. Here we use CRISPR-Cas9 mutagenesis to functionally test this association. We developed αMan2 knockouts and examined effects on both Wolbachia and virus levels, using dengue virus (DENV; Flaviviridae) and Mayaro virus (MAYV; Togaviridae). Wolbachia titres were significantly elevated in αMan2 knockout (KO) mosquitoes, but there were complex interactions with virus infection and replication. In Wolbachia-uninfected mosquitoes, the αMan2 KO mutation was associated with decreased DENV titres, but in a Wolbachia-infected background, the αMan2 KO mutation significantly increased virus titres. In contrast, the αMan2 KO mutation significantly increased MAYV replication in Wolbachia-uninfected mosquitoes and did not affect Wolbachia-mediated virus blocking. These results demonstrate that αMan2 modulates arbovirus infection in A. aegypti mosquitoes in a pathogen- and Wolbachia-specific manner, and that Wolbachia-mediated pathogen blocking is a complex phenotype dependent on the mosquito host genotype and the pathogen. These results have a significant impact for the design and use of Wolbachia-based strategies to control vector-borne pathogens.

Improved reference genome of Aedes aegypti informs arbovirus vector control.

Female Aedes aegypti mosquitoes infect more than 400 million people each year with dangerous viral pathogens including dengue, yellow fever, Zika and chikungunya. Progress in understanding the biology of mosquitoes and developing the tools to fight them has been slowed by the lack of a high-quality genome assembly. Here we combine diverse technologies to produce the markedly improved, fully re-annotated AaegL5 genome assembly, and demonstrate how it accelerates mosquito science. We anchored physical and cytogenetic maps, doubled the number of known chemosensory ionotropic receptors that guide mosquitoes to human hosts and egg-laying sites, provided further insight into the size and composition of the sex-determining M locus, and revealed copy-number variation among glutathione S-transferase genes that are important for insecticide resistance. Using high-resolution quantitative trait locus and population genomic analyses, we mapped new candidates for dengue vector competence and insecticide resistance. AaegL5 will catalyse new biological insights and intervention strategies to fight this deadly disease vector.

Comparison of Aedes aegypti arbovirus transmission thresholds in two communities with differing water supply infrastructure.

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.

Releasing incompatible males drives strong suppression across populations of wild and Wolbachia-carrying Aedes aegypti in Australia.

Releasing sterile or incompatible male insects is a proven method of population management in agricultural systems with the potential to revolutionize mosquito control. Through a collaborative venture with the "Debug" Verily Life Sciences team, we assessed the incompatible insect technique (IIT) with the mosquito vector Aedes aegypti in northern Australia in a replicated treatment control field trial. Backcrossing a US strain of Ae. aegypti carrying Wolbachia wAlbB from Aedes albopictus with a local strain, we generated a wAlbB2-F4 strain incompatible with both the wild-type (no Wolbachia) and wMel-Wolbachia Ae. aegypti now extant in North Queensland. The wAlbB2-F4 strain was manually mass reared with males separated from females using Verily sex-sorting technologies to obtain no detectable female contamination in the field. With community consent, we delivered a total of three million IIT males into three isolated landscapes of over 200 houses each, releasing ∼50 males per house three times a week over 20 wk. Detecting initial overflooding ratios of between 5:1 and 10:1, strong population declines well beyond 80% were detected across all treatment landscapes when compared to controls. Monitoring through the following season to observe the ongoing effect saw one treatment landscape devoid of adult Ae. aegypti early in the season. A second landscape showed reduced adults, and the third recovered fully. These encouraging results in suppressing both wild-type and wMel-Ae. aegypti confirms the utility of bidirectional incompatibility in the field setting, show the IIT to be robust, and indicate that the removal of this arbovirus vector from human-occupied landscapes may be achievable.

Aedes albopictus is a competent vector of five arboviruses affecting human health, greater Paris, France, 2023.

Aedes albopictus collected in 2023 in the greater Paris area (Île-de-France) were experimentally able to transmit five arboviruses: West Nile virus from 3 days post-infection (dpi), chikungunya virus and Usutu virus from 7 dpi, dengue virus and Zika virus from 21 dpi. Given the growing number of imported dengue cases reported in early 2024 in France, surveillance of Ae. albopictus should be reinforced during the Paris Olympic Games in July, when many international visitors including from endemic countries are expected.

The SUMOylation pathway suppresses arbovirus replication in Aedes aegypti cells.

Mosquitoes are responsible for the transmission of many clinically important arboviruses that cause significant levels of annual mortality and socioeconomic health burden worldwide. Deciphering the mechanisms by which mosquitoes modulate arbovirus infection is crucial to understand how viral-host interactions promote vector transmission and human disease. SUMOylation is a post-translational modification that leads to the covalent attachment of the Small Ubiquitin-like MOdifier (SUMO) protein to host factors, which in turn can modulate their stability, interaction networks, sub-cellular localisation, and biochemical function. While the SUMOylation pathway is known to play a key role in the regulation of host immune defences to virus infection in humans, the importance of this pathway during arbovirus infection in mosquito vectors, such as Aedes aegypti (Ae. aegypti), remains unknown. Here we characterise the sequence, structure, biochemical properties, and tissue-specific expression profiles of component proteins of the Ae. aegypti SUMOylation pathway. We demonstrate significant biochemical differences between Ae. aegypti and Homo sapiens SUMOylation pathways and identify cell-type specific patterns of SUMO expression in Ae. aegypti tissues known to support arbovirus replication. Importantly, depletion of core SUMOylation effector proteins (SUMO, Ubc9 and PIAS) in Ae. aegypti cells led to enhanced levels of arbovirus replication from three different families; Zika (Flaviviridae), Semliki Forest (Togaviridae), and Bunyamwera (Bunyaviridae) viruses. Our findings identify an important role for mosquito SUMOylation in the cellular restriction of arboviruses that may directly influence vector competence and transmission of clinically important arboviruses.

Brazilian Aedes aegypti as a Competent Vector for Multiple Complex Arboviral Coinfections.

BACKGROUND: Aedes aegypti is a highly competent vector in the transmission of arboviruses, such as chikungunya, dengue, Zika, and yellow fever viruses, and causes single and coinfections in the populations of tropical countries. METHODS: The infection rate, viral abundance (VA), vector competence (VC), disseminated infection, and survival rate were recorded after single and multiple infections of the vector with 15 combinations of chikungunya, dengue, Zika, and yellow fever arboviruses. RESULTS: Infection rates were 100% in all single and multiple infection experiments, except in 1 triple coinfection that presented a rate of 50%. The VC and disseminated infection rate varied from 100% (in single and quadruple infections) to 40% (in dual and triple infections). The dual and triple coinfections altered the VC and/or VA of ≥1 arbovirus. The highest viral VAs were detected for a single infection with chikungunya. The VAs in quadruple infections were similar when compared with each respective single infection. A decrease in survival rates was observed in a few combinations. CONCLUSIONS: A. aegypti was able to host all single and multiple arboviral coinfections. The interference of the chikungunya virus suggests that distinct arbovirus families may have a significant role in complex coinfections.

Mosquito-borne arboviruses in Uganda: history, transmission and burden.

Mosquito-transmitted arboviruses constitute a large proportion of emerging infectious diseases that are both a public health problem and a threat to animal populations. Many such viruses were identified in East Africa, a region where they remain important and from where new arboviruses may emerge. We set out to describe and review the relevant mosquito-borne viruses that have been identified specifically in Uganda. We focused on the discovery, burden, mode of transmission, animal hosts and clinical manifestation of those previously involved in disease outbreaks. A search for mosquito-borne arboviruses detected in Uganda was conducted using search terms 'Arboviruses in Uganda' and 'Mosquitoes and Viruses in Uganda' in PubMed and Google Scholar in 2020. Twenty-four mosquito-borne viruses from different animal hosts, humans and mosquitoes were documented. The majority of these were from family Peribunyaviridae, followed by Flaviviridae, Togaviridae, Phenuiviridae and only one each from family Rhabdoviridae and Reoviridae. Sixteen (66.7%) of the viruses were associated with febrile illnesses. Ten (41.7%) of them were first described locally in Uganda. Six of these are a public threat as they have been previously associated with disease outbreaks either within or outside Uganda. Historically, there is a high burden and endemicity of arboviruses in Uganda. Given the many diverse mosquito species known in the country, there is also a likelihood of many undescribed mosquito-borne viruses. Next generation diagnostic platforms have great potential to identify new viruses. Indeed, four novel viruses, two of which were from humans (Ntwetwe and Nyangole viruses) and two from mosquitoes (Kibale and Mburo viruses) were identified in the last decade using next generation sequencing. Given the unbiased approach of detection of viruses by this technology, its use will undoubtedly be critically important in the characterization of mosquito viromes which in turn will inform other diagnostic efforts.

Mosquito-borne arboviruses in Uganda: history, transmission and burden.

Mosquito-transmitted arboviruses constitute a large proportion of emerging infectious diseases that are both a public health problem and a threat to animal populations. Many such viruses were identified in East Africa, a region where they remain important and from where new arboviruses may emerge. We set out to describe and review the relevant mosquito-borne viruses that have been identified specifically in Uganda. We focused on the discovery, burden, mode of transmission, animal hosts and clinical manifestation of those previously involved in disease outbreaks. A search for mosquito-borne arboviruses detected in Uganda was conducted using search terms 'Arboviruses in Uganda' and 'Mosquitoes and Viruses in Uganda' in PubMed and Google Scholar in 2020. Twenty-four mosquito-borne viruses from different animal hosts, humans and mosquitoes were documented. The majority of these were from family Peribunyaviridae, followed by Flaviviridae, Togaviridae, Phenuiviridae and only one each from family Rhabdoviridae and Reoviridae. Sixteen (66.7 %) of the viruses were associated with febrile illnesses. Ten (41.7 %) of them were first described locally in Uganda. Six of these are a public threat as they have been previously associated with disease outbreaks either within or outside Uganda. Historically, there is a high burden and endemicity of arboviruses in Uganda. Given the many diverse mosquito species known in the country, there is also a likelihood of many undescribed mosquito-borne viruses. New generation diagnostic platforms have great potential to identify new viruses. Indeed, four novel viruses, two of which were from humans (Ntwetwe and Nyangole viruses) and two from mosquitoes (Kibale and Mburo viruses) including the 2010 yellow fever virus (YFV) outbreak were identified in the last decade using next generation sequencing. Given the unbiased approach of detection of viruses by this technology, its use will undoubtedly be critically important in the characterization of mosquito viromes which in turn will inform other diagnostic efforts.

Arboviral central nervous system infections.

PURPOSE OF REVIEW: This review provides an overview of arthropod-borne virus (arbovirus) infections that are important causes of human neurological infections world-wide. As many of the individual viruses in a specific genus or family cause overlapping clinical syndromes, this review discusses important viruses in groups to highlight some of the similarities and differences in groups of neuroinvasive arbovirus infections. RECENT FINDINGS: Arboviruses that cause neurological infections in humans continue to emerge and distribute to new regions. The geographic range of the vectors, the hosts and subsequent arbovirus infections in humans continues to expand and evolve. As emerging arboviruses move into new geographic regions, it is important to examine the associated epidemiological and clinical impacts of these infections as they enter new populations. SUMMARY: Arboviruses from the Flaviviridae, Togaviridae and Bunyaviridae families continue to emerge and spread into new regions. The arboviruses within these virus families cause characteristic neuroinvasive diseases in human populations. A complete understanding of the epidemiological and clinical features of the neuroinvasive arboviruses is important such that these pathogens can be recognized and diagnosed in humans as they emerge. Ongoing research to develop rapid, accurate diagnostics, therapeutic options and vaccines for these pathogens is needed to address future outbreaks of disease in human populations.

Development and lifespan of Culicoides obsoletus s.s. (Meigen) and other livestock-associated species reared at different temperatures under laboratory conditions.

Culicoides Latreille (Diptera: Ceratopogonidae) transmit arboviruses affecting wild and domestic ruminants such as bluetongue (BTV) and Schmallenberg virus (SBV). The sub-adult development and lifespan of Culicoides obsoletus s.s. (Meigen), Culicoides circumscriptus Kieffer and Culicoides paolae Boorman were examined at three different temperatures under laboratory conditions. Insects were collected from field between spring and autumn 2015 in two livestock farms located in Majorca (Spain). Gravid females were held individually at 18, 25 or 30 °C. Low temperatures increased the adult lifespan, time to oviposit and rate of development, whereas high temperatures increased the number of eggs, successful pupation and adult emergence as well as the larvae growth rate. The results showed that C. obsoletus s.s. have optimum development at 18 °C, whereas the optimal rearing temperature for C. circumscriptus and C. paolae was under warmer conditions of 25-30 °C. Variations in temperature/humidity and assays with different materials and substrates for oviposition should be considered in future studies. Understanding the requirements of the different species of Culicoides optimizing the results should be of special interest for predicting environmental change effects on these species, in addition to determining the rearing conditions for candidate Culicoides vectors.

Arboviruses: How Saliva Impacts the Journey from Vector to Host.

Arthropod-borne viruses, referred to collectively as arboviruses, infect millions of people worldwide each year and have the potential to cause severe disease. They are predominately transmitted to humans through blood-feeding behavior of three main groups of biting arthropods: ticks, mosquitoes, and sandflies. The pathogens harbored by these blood-feeding arthropods (BFA) are transferred to animal hosts through deposition of virus-rich saliva into the skin. Sometimes these infections become systemic and can lead to neuro-invasion and life-threatening viral encephalitis. Factors intrinsic to the arboviral vectors can greatly influence the pathogenicity and virulence of infections, with mounting evidence that BFA saliva and salivary proteins can shift the trajectory of viral infection in the host. This review provides an overview of arbovirus infection and ways in which vectors influence viral pathogenesis. In particular, we focus on how saliva and salivary gland extracts from the three dominant arbovirus vectors impact the trajectory of the cellular immune response to arbovirus infection in the skin.

Low toxicity and high efficacy in use of novel approaches to control Aedes aegypti.

Arthropod-borne viruses are a group of etiologic agents accounting for different incapacitating diseases that progress to severe and lethal forms in animal and human targets consequently representing a significant burden on public health and global economies. Although attempts were undertaken to combat Aedes aegypti, the primary urban mosquito vector of several life-threatening diseases, the misuse of chemical pesticides, development of resistance, and toxicity on non-target species still need to be overcome. In this context, it is imperative for development of long-lasting, novel approaches envisioning effective control of Aedes aegypti, mainly in endemic regions. Thus, the present review was undertaken to describe safe and eco-friendly approaches as potential weapons against Aedes aegypti. Accordingly, the findings discussed indicated that biological larvicides and genetic engineering technologies constitute noteworthy alternatives of future mosquito-borne arbovirus disease control efforts.

Infestation of an endemic arbovirus area by sympatric populations of Aedes aegypti and Aedes albopictus in Brazil.

BACKGROUND Aedes aegypti and Aedes albopictus are the most important arbovirus vectors in the world. OBJECTIVES This study aimed to investigate and compare the infestation pattern of these species in a neighbourhood of Recife, Brazil, endemic for arboviruses in 2005 (T1) and 2013 (T2). METHODS Infestation, distribution and relative abundance of these sympatric species were recorded by egg collection using a network of 59 sentinel ovitraps (s-ovt) at fixed sampling stations for 12 months in T1 and T2. FINDINGS A permanent occupation pattern was detected which was characterised by the presence of egg-laying females of one or both species with a high ovitrap positivity index (94.3 to 100%) throughout both years analysed. In terms of abundance, the total of eggs collected was lower (p < 0.005) in T2 (146,153) than in T1 (281,103), although ovitraps still displayed a high index of positivity. The spatial distribution showed the presence of both species in 65.1% of the 148 s-ovt assessed, while a smaller number of traps exclusively contained Ae. aegypti (22%) or Ae. albopictus (13.2%) eggs. MAIN CONCLUSIONS Our comparative analysis demonstrated the robustness of the spatial occupation and permanence of Ae. aegypti and Ae. albopictus populations in this endemic urban area.

Plant Natural Products for the Control of Aedes aegypti: The Main Vector of Important Arboviruses.

The mosquito species Aedes aegypti is one of the main vectors of arboviruses, including dengue, Zika and chikungunya. Considering the deficiency or absence of vaccines to prevent these diseases, vector control remains an important strategy. The use of plant natural product-based insecticides constitutes an alternative to chemical insecticides as they are degraded more easily and are less harmful to the environment, not to mention their lower toxicity to non-target insects. This review details plant species and their secondary metabolites that have demonstrated insecticidal properties (ovicidal, larvicidal, pupicidal, adulticidal, repellent and ovipositional effects) against the mosquito, together with their mechanisms of action. In particular, essential oils and some of their chemical constituents such as terpenoids and phenylpropanoids offer distinct advantages. Thiophenes, amides and alkaloids also possess high larvicidal and adulticidal activities, adding to the wealth of plant natural products with potential in vector control applications.

Arbovirus lifecycle in mosquito: acquisition, propagation and transmission.

Mosquitoes are haematophagous vectors for hundreds of pathogenic viruses that are aetiological agents of human diseases. In nature, mosquito-borne viruses maintain a lifecycle between mosquitoes and vertebrate animals. Viruses are acquired by a naive mosquito from an infected host by blood meals and then propagate extensively in the mosquito's tissues. This mosquito then becomes a virus reservoir and is competent to transmit the viruses to a naive vertebrate host through the next blood meal. To survive in and efficiently cycle between two distinct host environments, mosquito-borne viruses have evolved delicate and smart strategies to comprehensively exploit host and vector factors. Here, we provide an update on recent studies of the mechanisms of virus survival in, acquisition and transmission by mosquitoes.

From dengue to Zika: the wide spread of mosquito-borne arboviruses.

The worldwide invasion of arthropod-borne viruses (arboviruses) in recent decades is responsible for emerging public health threats. Some factors like climate change, urbanisation and uncontrolled population growth are fuelling their widespread. Arboviruses incorporate a vast collection of genetically diverse viral pathogens including that of dengue, Zika and chikungunya. These viruses are peculiar as they are zoonotic and are a serious harm to the society, with no particular therapy to neutralise their effect. So it is the need of the hour to develop an effective treatment against infections caused by them. This review focuses on some of the common families of mosquito-borne arboviruses and their most known members that are a threat to mankind and discusses their genome organisation, worldwide spread and negative influence on public health.

Arboviruses and their related infections in China: A comprehensive field and laboratory investigation over the last 3 decades.

Since the 1980s, a comprehensive field and laboratory investigation has been conducted throughout China, and a total of 29 virus species belonging to 7 families and 13 genera were identified through virological, morphological, and immunological methods, as well as whole-genome sequencing and molecular genetic analyses. Most of the virus isolates belong to 9 genera in the families Flaviviridae, Bunyaviridae, Togaviridae, and Reoviridae. Among them, 4 genera (Orthobunyavirus, Bunyavirus, Phlebovirus, and Nairovirus) belong to the family Bunyaviridae and 3 genera (Seadonavirus, Orbivirus, and Cypovirus) belong to the family Reoviridae. Analyses of the relationships between viruses and human/animal diseases indicated that Japanese encephalitis virus, dengue virus, severe fever with thrombocytopenia syndrome virus, tick-borne encephalitis virus, Crimean-Congo hemorrhagic fever virus, West Nile virus, and Tahyna virus can cause human and animal infections and disease epidemics in China. This review systematically introduces the current status of the diversity and geographical distribution of arboviruses and vectors in China. In addition, our results provide strong technical support for the prevention and control of arboviral diseases, the treatment of epidemics, and the early warning and prediction of diseases, and so they are significant for the control and prevention of arboviral diseases in Asia and around the world.

State estimators for some epidemiological systems.

We consider a class of epidemiological models that includes most well-known dynamics for directly transmitted diseases, and some reduced models for indirectly transmitted diseases. We then propose a simple observer that can be applied to models in this class. The error analysis of this observer leads to a non-autonomous error equation, and a new bound for fundamental matrices is also presented. We analyse and implement this observer in two examples: the classical SIR model, and a reduced Bailey-Dietz model for vector-borne diseases. In both cases we obtain arbitrary exponential convergence of the observer. For the latter model, we also applied the observer to recover the number of susceptible using dengue infection data from a district in the city of Rio de Janeiro.