Emerging arboviruses: Why today?

Targeting histone epigenetics to control viral infections

During the past decades, many studies have significantly broadened our understanding of complex virus-host interactions to control chromatin structure and dynamics.1, 2 However, the role and impact of such modifications during viral infections is not fully revealed. Indeed, this type of regulation is bidirectional between the virus and the host. While viral replication and gene expression are significantly impacted by histone modifications on the viral chromatin,³ studies have shown that some viral pathogens dynamically manipulate cellular epigenetic factors to enhance their own survival and pathogenesis, as well as escape the immune system defense lines.⁴ In this dynamic, histone posttranslational modifications (PTMs) appear to play fundamental roles in the regulation of chromatin structure and recruitment of other factors.⁵ Genuinely, those PTMs play a vital role in lytic infection, latency reinforcement, or, conversely, viral reactivation.⁶ In this chapter, we will examine and review the involvement of histone modifications as well as their potential manipulation to control infections during various viral life cycle stages, highlighting their prospective implications in the clinical management of human immunodeficiency virus (HIV), herpes simplex virus (HSV), human cytomegalovirus (HCMV), hepatitis B and C viruses (HBV and HCV, respectively), Epstein–Barr virus (EBV), and other viral diseases. Targeting histone modifications is critical in setting the treatment of chronic viral infections with both lytic and latent stages (HIV, HCMV, HSV, RSV), virus-induced cancers (HBV, HCV, EBV, KSHV, HPV), and epidemic/emerging viruses (e.g. influenza virus, arboviruses).

Viral Emerging Pathogen Evolution

The emergence of emerging and reemerging infectious diseases throughout history has been the product of the interaction of infectious agents, immunity, selective pressure, and environmental factors. The origin of the viral ancestors remains controversial, the debate remains whether the viruses existed before their host cells, evolved as molecular structures that adapted to the intracellular development or of the cells that infected or housed them as hosts. The nature of the viruses could propose a hypothetical evolutionary model based on the way they parasitize cells and the way they fuse with their host cells. So far there are no “universal” viral genes that have not allowed the hypotheses of the “common viral ancestor” to be conclusive. Insects have a special role in understanding viral evolution and how they became pathogens, suggesting a coevolutionary scenario of colonization that would initially allow the survival of viruses and later an ecological niche required for the cycle of virus replication. The coevolution of viruses and defense systems of hosts represents a fundamental role in the evolution of both viruses and host cells, a kind of arms race between viruses and hosts, and the deescalation of that war could explain the coexistence of viruses and hosts. Viruses are playing an important role in the understanding of cell evolution and have earned the right to be included in the tree of life. The aim of this chapter is to review the viral evolution and the insects as host.

Recombination of B- and T-cell epitope-rich loci from Aedes- and Culex-borne flaviviruses shapes Zika virus epidemiology

Sporadic human Zika virus (ZIKV) infections have been recorded in Africa and Asia since the 1950s. Major epidemics occurred only after ZIKV emerged in the Pacific islands and spread to the Americas. Specific biological determinants of the explosive epidemic nature of ZIKV have not been identified. Phylogenetic studies revealed incongruence in ZIKV placement in relation to Aedes-borne dengue viruses (DENV) and Culex-borne flaviviruses. We hypothesized that this incongruence reflects interspecies recombination resulting in ZIKV evasion of cross-protective T-cell immunity. We investigated ZIKV phylogenetic incongruence in relation to: DENV T-cell epitope maps experimentally identified ex vivo, published B-cell epitope loci, and CD8⁺ T-cell epitopes predicted in silico for mosquito-borne flaviviruses. Our findings demonstrate that the ZIKV proteome is a hybrid of Aedes-borne DENV proteins interspersed amongst Culex-borne flavivirus proteins derived through independent interspecies recombination events. These analyses infer that DENV-associated proteins in the ZIKV hybrid proteome generated immunodominant human B-cell responses, whereas ZIKV recombinant derived Culex-borne flavivirus-associated proteins generated immunodominant CD8⁺ and/or CD4⁺ T-cell responses. In silico CD8⁺ T-cell epitope ZIKV cross-reactive prediction analyses verified this observation. We propose that by acquiring cytotoxic T-cell epitope-rich regions from Culex-borne flaviviruses, ZIKV evaded DENV-generated T-cell immune cross-protection. Thus, Culex-borne flaviviruses, including West Nile virus and Japanese encephalitis virus, might induce cross-protective T-cell responses against ZIKV. This would explain why explosive ZIKV epidemics occurred in DENV-endemic regions of Micronesia, Polynesia and the Americas where Culex-borne flavivirus outbreaks are infrequent and why ZIKV did not cause major epidemics in Asia where Culex-borne flaviviruses are widespread.

Ecology of West Nile Virus in the Danube Delta, Romania: Phylogeography, Xenosurveillance and Mosquito Host-Feeding Patterns

The ecology of West Nile virus (WNV) in the Danube Delta Biosphere Reserve (Romania) was investigated by combining studies on the virus genetics, phylogeography, xenosurveillance and host-feeding patterns of mosquitoes. Between 2014 and 2016, 655,667 unfed and 3842 engorged mosquito females were collected from four sampling sites. Blood-fed mosquitoes were negative for WNV-RNA, but two pools of unfed Culex pipiens s.l./torrentium collected in 2014 were tested positive. Our results suggest that Romania experienced at least two separate WNV lineage 2 introductions: from Africa into Danube Delta and from Greece into south-eastern Romania in the 1990s and early 2000s, respectively. The genetic diversity of WNV in Romania is primarily shaped by in situ evolution. WNV-specific antibodies were detected for 19 blood-meals from dogs and horses, but not from birds or humans. The hosts of mosquitoes were dominated by non-human mammals (19 species), followed by human and birds (23 species). Thereby, the catholic host-feeding pattern of Culex pipiens s.l./torrentium with a relatively high proportion of birds indicates the species’ importance as a potential bridge vector. The low virus prevalence in combination with WNV-specific antibodies indicate continuous, but low activity of WNV in the Danube Delta during the study period.

Serological evidence of arboviruses and coccidia infecting horses in the Amazonian region of Brazil

Background

Arboviruses and protozoans can cause neurologic disorders in horses. In Brazilian Amazon, several horses presenting signs compatible with disorders caused by these infectious agents have been observed.

Objective

To contribute to the knowledge of this epidemiological picture, we sought to construct a serological diagnostic panel for neurotrophic infectious agents in local horses.

Material and methods

A total of 213 blood samples from horses were collected from 29 farms in three municipalities. Samples were evaluated and considered positive when they met the following criteria: titers ≥ 1:80 with the indirect fluorescent antibody test (IFAT) for apicomplexan protozoans; positive recombinant enzyme-linked immunosorbent assay (ELISA) with subsequent titers ≥ 1:10 by the PRNt for viruses; and detection under direct microscopic examination for Trypanosoma evansi.

Results

No horses were found to be infected by T. evansi, and only two were infected Toxoplasma gondii and/or Neospora spp. The highest protozoan infection rate was observed for Sarcocystis neurona (40.3%; n = 86/213). Among the positive ELISA samples tested by the plaque reduction neutralization test (PRNT₉₀), 92% (n = 76/83) were positive for St Louis Encephalitis virus, 43% (n = 6/14) were positive for West Nile virus and 33% (n = 16/48) were positive for Mayaro virus. Eighteen percent (n = 39/213) of horses were co-infected by S. neurona and at least one arbovirus, particularly SLEV and/or MAYV.

Conclusion

Samples positive for SLEV associated with S. neurona, including samples from horses that had recovered from neurological signs were frequent, and must be considered when investigating the possible causes of neurological diseases in South Roraima horses.

Insights into the Host Specificity of Mosquito-Borne Flaviviruses Infecting Wild Mammals

Mosquito-borne flaviviruses (MBFVs) are of public and animal health concern because they cause millions of human deaths annually and impact domestic animals and wildlife globally. MBFVs are phylogenetically divided into two clades, one is transmitted by Aedes mosquitoes (Ae-MBFVs) associated with mammals and the other by Culex mosquitoes (Cx-MBFVs) associated with birds. However, this assumption has not been evaluated. Here, we synthesized 79 published reports of MBFVs from wild mammals, estimating their host. Then, we tested whether the host specificity was biased to sampling and investigation efforts or to phylogenetic relationships using a viral phylogenetic tree drawn from analyzing whole flavivirus genomes obtained in GenBank. We found in total 18 flaviviruses, nine related to Aedes spp. and nine to Culex spp. infecting 129 mammal species. Thus, this supports that vectors are transmitting MBFV across available host clades and that ornithophilic mosquitoes are readily infecting mammals. Although most of the mosquito species are generalists in their host-feeding preferences, we also found a certain degree of MBFV's specificity, as most of them infect closely related mammal species. The present study integrates knowledge regarding MBFVs, and it may help to understand their transmission dynamics between viruses, vectors, and mammal hosts.

Use of MALDI-TOF MS to identify the culturable midgut microbiota of laboratory and wild mosquitoes

Mosquitoes are responsible for transmitting many pathogens to humans and Aedes aegypti, Aedes albopictus and Culex quinquefasciatus are important vectors in the world. The microbiota plays an important role in developmental studies that involve impacts on the biological cycle of mosquitoes and vector control strategies. In this study, the aim was to understand the environment plays in the microbiota culturable diversity of Aedes aegytpi, Aedes albopictus and Culex quinquefasciatus. Midgut of studied mosquitoes (laboratory-reared and wild) were dissected and analyzed by MALDI-TOF MS to identify the microbiota. Most of the bacteria identified in the microbiota of mosquitoes from the laboratory and field belong to the phylum Proteobacteria. We reported on the microbial diversity among the mosquito species studied where Cx. quinquefasciatus and Ae. albopictus show greater bacterial similarity. The genus Rahnella was present in all mosquito species studied, both in those from the laboratory and those from the wild. Bacillus, Ewingella, Microccocus, Klebsiella and Pantoea are genera was predominant among the mosquitoes studied. The difference of microbiota diversity between mosquitoes laboratory-reared and wild shows that the environment plays an important role in the acquisition of bacteria, mainly in Ae. aegypti and Cx. quinquefasciatus.

Meta-Transcriptomic Comparison of the RNA Viromes of the Mosquito Vectors Culex pipiens and Culex torrentium in Northern Europe

Mosquitoes harbor an extensive diversity of ‘insect-specific’ RNA viruses in addition to those important to human and animal health. However, because most studies of the mosquito virome have been conducted at lower latitudes, little is known about the diversity and evolutionary history of RNA viruses sampled from mosquitoes in northerly regions. Here, we compared the RNA virome of two common northern mosquito species, Culex pipiens and Culex torrentium, collected in south-central Sweden. Following bulk RNA-sequencing (meta-transcriptomics) of 12 libraries, comprising 120 specimens of Cx. pipiens and 150 specimens of Cx. torrentium, we identified 40 viruses (representing 14 virus families) of which 28 were novel based on phylogenetic analysis of the RNA-dependent RNA polymerase (RdRp) protein. Hence, we documented similar levels of virome diversity as in mosquitoes sampled from the more biodiverse lower latitudes. Many viruses were also related to those sampled on other continents, indicative of a widespread global movement and/or long host–virus co-evolution. Although the two mosquito species investigated have overlapping geographical distributions and share many viruses, several viruses were only found at a specific location at this scale of sampling, such that local habitat and geography may play an important role in shaping viral diversity in Culex mosquitoes.

Urbanization creates diverse aquatic habitats for immature mosquitoes in urban areas

Global increases in temperatures and urbanization are impacting the epidemiology of mosquito-borne diseases. Urbanization processes create suitable habitats for vector mosquitoes in which there are a reduced number of predators, and human hosts are widely available. We hypothesize that mosquito vector species, especially Aedes aegypti, are locally concentrated primarily in those specific habitats at the neighborhood levels that provide suitable conditions and environmental resources needed for mosquito survival. Determining how mosquito vector species composition and abundance depend on environmental resources across habitats addresses where different types of vector control need to be applied. Therefore, our goal was to analyze and identify the most productive aquatic habitats for mosquitoes in Miami-Dade County, Florida. Immature mosquito surveys were conducted throughout Miami-Dade County from April 2018 to June 2019, totaling 2,488 inspections. Mosquitoes were collected in 76 different types of aquatic habitats scattered throughout 141 neighborhoods located in the urbanized areas of Miami-Dade County. A total of 44,599 immature mosquitoes were collected and Ae. aegypti was the most common and abundant species, comprising 43% of all specimens collected. Aedes aegypti was primarily found in buckets, bromeliads, and flower pots, concentrated in specific neighborhoods. Our results showed that aquatic habitats created by anthropogenic land-use modifications (e.g., ornamental bromeliads, buckets, etc.) were positively correlated with the abundance of Ae. aegypti. This study serves to identify how vector mosquitoes utilize the resources available in urban environments and to determine the exact role of these specific urban features in supporting populations of vector mosquito species. Ultimately, the identification of modifiable urban features will allow the development of targeted mosquito control strategies optimized to preventatively control vector mosquitoes in urban areas.

A viral metagenomic analysis reveals rich viral abundance and diversity in mosquitoes from pig farms

Mosquitoes harbour a diversity of viruses and are responsible for several mosquito-borne viral diseases of humans and animals, thereby leading to major public health concerns, and significant economic losses across the globe. Viral metagenomics offers a great opportunity for bulk analysis of viral genomes retrieved directly from environmental samples. In this study, we performed a viral metagenomic analysis of five pools of mosquitoes belonging to Aedes, Anopheles and Culex species, collected from different pig farms in the vicinity of Shanghai, China, to explore the viral community carried by mosquitoes. The resulting metagenomic data revealed that viral community in the mosquitoes was highly diverse and varied in abundance among pig farms, which comprised of more than 48 viral taxonomic families, specific to vertebrates, invertebrates, plants, fungi, bacteria and protozoa. In addition, a considerable number of viral reads were related to viruses that are not classified by host. The read sequences related to animal viruses included parvoviruses, anelloviruses, circoviruses, flavivirus, rhabdovirus and seadornaviruses, which might be taken up by mosquitoes from viremic animal hosts during blood feeding. Notably, sample G1 contained the most abundant sequence related to Banna virus, which is of public health interest because it causes encephalitis in humans. Furthermore, non-classified viruses also shared considerable virus sequences in all the samples, presumably belonging to unexplored virus category. Overall, the present study provides a comprehensive knowledge of diverse viral populations carried by mosquitoes at pig farms, which is a potential source of diseases for mammals including humans and animals. These viral metagenomic data are valuable for assessment of emerging and re-emerging viral epidemics.

Assessment of metagenomic Nanopore and Illumina sequencing for recovering whole genome sequences of chikungunya and dengue viruses directly from clinical samples

Background

The recent global emergence and re-emergence of arboviruses has caused significant human disease. Common vectors, symptoms and geographical distribution make differential diagnosis both important and challenging.

Aim

To investigate the feasibility of metagenomic sequencing for recovering whole genome sequences of chikungunya and dengue viruses from clinical samples.

Methods

We performed metagenomic sequencing using both the Illumina MiSeq and the portable Oxford Nanopore MinION on clinical samples which were real-time reverse transcription-PCR (qRT-PCR) positive for chikungunya (CHIKV) or dengue virus (DENV), two of the most important arboviruses. A total of 26 samples with a range of representative clinical Ct values were included in the study.

Results

Direct metagenomic sequencing of nucleic acid extracts from serum or plasma without viral enrichment allowed for virus identification, subtype determination and elucidated complete or near-complete genomes adequate for phylogenetic analysis. One PCR-positive CHIKV sample was also found to be coinfected with DENV.

Conclusions

This work demonstrates that metagenomic whole genome sequencing is feasible for the majority of CHIKV and DENV PCR-positive patient serum or plasma samples. Additionally, it explores the use of Nanopore metagenomic sequencing for DENV and CHIKV, which can likely be applied to other RNA viruses, highlighting the applicability of this approach to front-line public health and potential portable applications using the MinION.

External Control Viral-Like Particle Construction for Detection of Emergent Arboviruses by Real-Time Reverse-Transcription PCR

Arboviruses have been emerging and reemerging worldwide, predominantly in tropical and subtropical areas. As many arbovirus infections, including dengue (DENV), Zika (ZIKV), and chikungunya (CHIKV), have similar signs and symptoms, clinical diagnosis of arbovirus infections is challenging. Therefore, reliable laboratory tests are necessary to improve the clinical management of patients with suspected arbovirus infections. Real-time reverse-transcription PCR (RT-qPCR) is among the more effective methods to distinguish these viruses. The aim of this study was to construct a unique positive external control derived from a unique plasmid using genetic engineering for specific use in RT-qPCR assays to detect Zika, dengue (1-4), and chikungunya. An external control derived from the MS2 bacteriophage was constructed using sequences from arbovirus and human genomes. Laboratories were asked to test the control in the ZDC Biomol kit, a RT-qPCR kit which is able to detect Zika, dengue serotypes 1-4, chikungunya, and an internal human control. RNA extracted from the external control was able to be amplified and detected in RT-qPCR assays for each virus detected by using the ZDC Biomol kit. The external control, samples from viral culture, and infected patient samples display similar amplification using this assay. The pET47b(+)MS2-ZDC vector is a viable expression system for the production of external control viral-like particles (MS2-ZDC). The RNA from the recombinant particles can be easily extracted and can function as a tool to validate all steps of process from the extraction to the amplification of all targets in specific reaction. Thus, the MS2-ZDC particles are laboratory-safe in order to avoid risk for operators, and the phages are effective as positive control for use in the ZDC Biomol kit amplifying all kit targets making them effective for commercial profile.

Sylvatic cycles of arboviruses in non-human primates

Arboviruses infecting people primarily exist in urban transmission cycles involving urban mosquitoes in densely populated tropical regions. For dengue, chikungunya, Zika and yellow fever viruses, sylvatic (forest) transmission cycles also exist in some regions and involve non-human primates and forest-dwelling mosquitoes. Here we review the investigation methods and available data on sylvatic cycles involving non-human primates and dengue, chikungunya, Zika and yellow fever viruses in Africa, dengue viruses in Asia and yellow fever virus in the Americas. We also present current putative data that Mayaro, o'nyong'nyong, Oropouche, Spondweni and Lumbo viruses exist in sylvatic cycles.

Vector Competence: What Has Zika Virus Taught Us?

The unprecedented outbreak of Zika virus (ZIKV) infection in the Americas from 2015 to 2017 prompted the publication of a large body of vector competence data in a relatively short period of time. Although differences in vector competence as a result of disparities in mosquito populations and viral strains are to be expected, the limited competence of many populations of the urban mosquito vector, Aedes aegypti, from the Americas (when its susceptibility is viewed relative to other circulating/reemerging mosquito-borne viruses such as dengue (DENV), yellow fever (YFV), and chikungunya viruses (CHIKV)) has proven a paradox for the field. This has been further complicated by the lack of standardization in the methodologies utilized in laboratory vector competence experiments, precluding meta-analyses of this large data set. As the calls for the standardization of such studies continue to grow in number, it is critical to examine the elements of vector competence experimental design. Herein, we review the various techniques and considerations intrinsic to vector competence studies, with respect to contemporary findings for ZIKV, as well as historical findings for other arboviruses, and discuss potential avenues of standardization going forward.

Updated Phylogeny of Chikungunya Virus Suggests Lineage-Specific RNA Architecture

Chikungunya virus (CHIKV), a mosquito-borne alphavirus of the family Togaviridae, has recently emerged in the Americas from lineages from two continents: Asia and Africa. Historically, CHIKV circulated as at least four lineages worldwide with both enzootic and epidemic transmission cycles. To understand the recent patterns of emergence and the current status of the CHIKV spread, updated analyses of the viral genetic data and metadata are needed. Here, we performed phylogenetic and comparative genomics screens of CHIKV genomes, taking advantage of the public availability of many recently sequenced isolates. Based on these new data and analyses, we derive a revised phylogeny from nucleotide sequences in coding regions. Using this phylogeny, we uncover the presence of several distinct lineages in Africa that were previously considered a single one. In parallel, we performed thermodynamic modeling of CHIKV untranslated regions (UTRs), which revealed evolutionarily conserved structured and unstructured RNA elements in the 3'UTR. We provide evidence for duplication events in recently emerged American isolates of the Asian CHIKV lineage and propose the existence of a flexible 3'UTR architecture among different CHIKV lineages.

Climate drives spatial variation in Zika epidemics in Latin America

Between 2015 and 2017, Zika virus spread rapidly through populations in the Americas with no prior exposure to the disease. Although climate is a known determinant of many Aedes-transmitted diseases, it is currently unclear whether climate was a major driver of the Zika epidemic and how climate might have differentially impacted outbreak intensity across locations within Latin America. Here, we estimated force of infection for Zika over time and across provinces in Latin America using a time-varying susceptible–infectious–recovered model. Climate factors explained less than 5% of the variation in weekly transmission intensity in a spatio-temporal model of force of infection by province over time, suggesting that week to week transmission within provinces may be too stochastic to predict. By contrast, climate and population factors were highly predictive of spatial variation in the presence and intensity of Zika transmission among provinces, with pseudo-R² values between 0.33 and 0.60. Temperature, temperature range, rainfall and population size were the most important predictors of where Zika transmission occurred, while rainfall, relative humidity and a nonlinear effect of temperature were the best predictors of Zika intensity and burden. Surprisingly, force of infection was greatest in locations with temperatures near 24°C, much lower than previous estimates from mechanistic models, potentially suggesting that existing vector control programmes and/or prior exposure to other mosquito-borne diseases may have limited transmission in locations most suitable for Aedes aegypti, the main vector of Zika, dengue and chikungunya viruses in Latin America.

The discovery and global distribution of novel mosquito-associated viruses in the last decade (2007-2017)

In the last decade, virus hunting and discovery has gained pace. This achievement has been driven by three major factors: (a) advancements in sequencing technologies, (b) scaled-up routine arbovirus surveillance strategies, and (c) the "hunt" for emerging pathogens and novel viruses. Many novel viruses have been discovered from a myriad of hosts, vectors, and environmental samples. To help promote understanding of the global diversity and distribution of mosquito-associated viruses and facilitate future studies, we review mosquito-associated viruses discovered between years 2007 and 2017, across the world. In the analyzed period, novel mosquito-associated viruses belonging to 25 families and a general group of unclassified viruses were categorized. The top three discovered novel mosquito-associated viruses belonged to families Flaviviridae (n=32), Rhabdoviridae (n=16), and Peribunyaviridae (n=14). Also, 67 unclassified viruses were reported. Majority of these novel viruses were identified from Culex spp, Anopheles spp, Aedes spp, and Mansonia spp mosquitoes, respectively. Notably, the number of these discovered novels is not representative of intercontinental virus diversity but rather is influenced by the number of studies done in the study period. Some of these newly discovered mosquito-associated viruses have medical significance, either directly or indirectly. For instance, in the study period, 14 novel mosquito-borne viruses that infect mammalian cells in vitro were reported. These viruses pose a danger to the global health security on emerging viral diseases. On the other hand, some of the newly discovered insect specific viruses described herein have potential application as future biocontrol and vaccine agents against known pathogenic arboviruses. Overall, this review outlines the crucial role played by mosquitoes as viral vectors in the global virosphere.

A yellow flag on the horizon: The looming threat of yellow fever to North America

OBJECTIVES

Yellow fever virus historically was a frequent threat to American and European coasts. Medical milestones such as the discovery of mosquitoes as vectors and subsequently an effective vaccine significantly reduced its incidence, in spite of which, thousands of cases of this deathly disease still occur regularly in Sub-Saharan Africa and the Amazonian basin in South America, which are usually not reported. An urban outbreak in Angola, consecutive years of increasing incidence near major Brazilian cities, and imported cases in China, South America and Europe, have brought this virus back to the global spotlight. The aim of this article is to underline that the preventive YFV measures, such as vaccination, need to be carefully revised in order to minimize the risks of new YFV outbreaks, especially in urban or immunologically vulnerable places. Furthermore, this article highlights the diverse factors that have favored the spread of other Aedes spp.-associated arboviral diseases like Dengue, Chikungunya and Zika, to northern latitudes causing epidemics in the United States and Europe, emphasizing the possibility that YFV might follow the path of these viruses unless enhanced surveillance and efficient control systems are urgently initiated.

Arboviruses in the East African Community partner states: a review of medically important mosquito-borne Arboviruses

Mosquito-borne diseases, including arbovirus-related diseases, make up a large proportion of infectious disease cases worldwide, causing a serious global public health burden with over 700,000 deaths annually. Mosquito-borne arbovirus outbreaks can range from global to regional. In the East African Community (EAC) region, these viruses have caused a series of emerging and reemerging infectious disease outbreaks. Member states in the EAC share a lot in common including regional trade and transport, some of the factors highlighted to be the cause of mosquito-borne arbovirus disease outbreaks worldwide. In this review, characteristics of 24 mosquito-borne arboviruses indigenous to the EAC are reviewed, including lesser or poorly understood viruses, like Batai virus (BATV) and Ndumu virus (NDUV), which may escape their origins under perfect conditions to establish a foothold in new geographical locations. Factors that may influence the future spread of these viruses within the EAC are addressed. With the continued development observed in the EAC, strategies should be developed by the Community in improving mosquito and mosquito-borne arbovirus surveillance to prevent future outbreaks.

Long-term shifts in the seasonal abundance of adult Culicoides biting midges and their impact on potential arbovirus outbreaks

Surveillance of adult Culicoides biting midge flight activity is used as an applied ecological method to guide the management of arbovirus incursions on livestock production in Europe and Australia.To date the impact of changes in the phenology of adult vector activity on arbovirus transmission has not been defined. We investigated this at two sites in the UK, identifying 150,000 Culicoides biting midges taken from 2867 collections over a nearly 40 year timescale.Whilst we recorded no change in seasonal activity at one site, shifts in first adult appearance and last adult appearance increased the seasonal activity period of Culicoides species at the other site by 40 days over the time period.Lengthening of the adult activity season was driven by an increase in abundance of Culicoides and correlated with local increases in temperature and precipitation. This diversity in responses poses significant challenges for predicting future transmission and overwintering risk. Policy implications. Our analysis not only shows a dramatic and consistent increase in the adult active period of Culicoides biting midges, but also that this varies significantly between sites. This suggests broad-scale analyses alone are insufficient to understand the potential impacts of changes in climate on arbovirus vector populations. Understanding the impact of climate change on adult Culicoides seasonality and transmission of arboviruses requires the context of changes in a range of other local ecological drivers.

International proficiency trial demonstrates reliable Schmallenberg virus infection diagnosis in endemic and non-affected countries

Schmallenberg virus (SBV), an orthobunyavirus infecting ruminants, emerged in 2011 in Central Europe, spread very rapidly throughout the continent and established an endemic status, thereby representing a constant threat not only to the European livestock population, but also to neighboring countries. Hence, in endemically infected regions, the maintenance and regular verification of diagnostics is needed and in not yet affected regions, suitable diagnostic systems should be established to be prepared for a potential introduction of the disease. In addition, also for the trade of animals into free regions, highly reliable and sensitive diagnostics are of utmost importance. Therefore, a laboratory proficiency trial was initiated to allow for performance evaluations of test systems available for SBV-diagnostics, but also for evaluation of veterinary diagnostic laboratories performing those tests. Ten serum samples (six seropositive, four seronegative) were provided for serological analysis, four of the seropositive samples were provided undiluted, while the remaining samples represented 1/2 and 1/4 dilutions of one of the aforementioned samples in negative serum. Ten further sera (five virus-positive, five negative) were sent to the participants to be analyzed by SBV genome detection methods. A total of 48 diagnostic laboratories from 15 countries of three continents (Europe, Asia, North America) and three kit manufacturers participated in the SBV proficiency test, thereby generating 131 result sets, corresponding to 1310 individual results. The sample panel aimed for serological analysis was tested 72 times; the applied diagnostic methods comprised different commercial ELISAs and standard micro-neutralization tests. The sample set aimed for genome detection was analyzed in 59 approaches by various commercial or in-house (real-time) RT-PCR protocols. Antibody or genome positive samples were correctly identified in every case, independent of the applied diagnostic test system. For seronegative samples, three incorrect, false-positive test results were produced. Virus-negative samples tested false-positive in two cases. Thus, a very high diagnostic accuracy of 99.58% and 99.66% was achieved by the serological and virological methods, respectively. Hence, this ring trial demonstrated that reliable and robust SBV-diagnostics has been established in veterinary diagnostic laboratories in affected and non-affected countries.

Identification of a novel alphavirus related to the encephalitis complexes circulating in southern Brazil

In early 2017, an outbreak caused by an unknown and supposedly viral agent in the Marilena region of southern Brazil was investigated. Since the etiological agent causing the outbreak was not identified from human samples, mosquitoes from this region were collected. Three out of 121 mosquito pools collected from the region tested positive for alphavirus in molecular tests. Next generation sequencing results revealed the presence of a novel alphavirus, tentatively named here as Caainguá virus (CAAV). DNA barcoding analyses indicated that different species of Culex are hosts for CAAV. This new virus was basal to the New World encephalitic alphaviruses in a comprehensive and robust phylogenetic approach using complete genomes. Viral particles were observed in the cytosol and inside of intracellular compartments of cells in mosquito-derived cell cultures. Despite being noninfectious in vertebrate derived cell cultures, primary culturing of CAAV in human mononuclear cells suggests monocytes and lymphocytes as CAAV targets. However, the epidemiological link of CAAV on the human outbreak should be further explored.

Community Composition and Year-round Abundance of Vector Species of Mosquitoes make Miami-Dade County, Florida a Receptive Gateway for Arbovirus entry to the United States

Vector-borne diseases are a heavy burden to human-kind. Global warming and urbanization have a significant impact on vector-borne disease transmission, resulting in more severe outbreaks, and outbreaks in formerly non-endemic areas. Miami-Dade County, Florida was the most affected area in the continental United States during the 2016 Zika virus outbreak. Miami is an important gateway and has suitable conditions for mosquitoes year-round. Therefore, it was critical to establish and validate a surveillance system to guide and improve mosquito control operations. Here we assess two years of mosquito surveillance in Miami established after the 2016 Zika virus outbreak. Our results show that the most abundant mosquito species are either well adapted to urban environments or are adapting to it. The five most abundant species comprised 85% of all specimens collected, with four of them being primary vectors of arboviruses. Aedes aegypti and Culex quinquefasciatus were found year-round throughout Miami regardless of urbanization level, vegetation, or socioeconomic variations. This study serves as a foundation for future efforts to improve mosquito surveillance and control operations.

Evidence for Host Epigenetic Signatures Arising From Arbovirus Infections: A Systematic Review

Background: Arbovirus infections have steadily become a major pandemic threat. This study aimed at investigating the existence of host epigenetic markers arising from the principal arboviruses infections impacting on human health. We set to systematically review all published evidence describing any epigenetic modifications associated with infections from arboviruses, including, but not limited to, microRNAs, DNA methylation, and histone modifications. Methods: A comprehensive search was conducted using the electronic databases PubMed, Science Direct and Cochrane Library from inception to January 4th, 2018. We included reports describing original in vivo or in vitro studies investigating epigenetic changes related to arbovirus infections in either clinical subjects or human cell lines. Studies investigating epigenetic modifications related to the virus or the arthropod vector were excluded. A narrative synthesis of the findings was conducted, contextualizing comparative evidence from in vitro and in vivo studies. Results: A total of 853 unique references were identified and screened by two independent researchers. Thirty-two studies met the inclusion criteria and were reviewed. The evidence was centered mainly on microRNA and DNA methylation signatures implicated with secondary Dengue fever. Evidence for recent epidemic threats, such as the infections by Zika or Chikungunya viruses is still scant. Conclusions: Major epigenetic alterations found on arboviruses infections were miR-146, miR-30e and the Dicer complex. However, existing studies frequently tested distinct hypotheses resulting in a heterogeneity of methodological approaches. Whilst epigenetic signatures associated with arbovirus infections have been reported, existing studies have largely focused on a small number of diseases, particularly dengue. Validation of epigenetic signatures have an untapped potential, but concerted investigations are certainly required to deliver robust candidates of clinical utility for diagnosis, staging and prognosis of specific arboviral diseases.

Vertically transmitted chikungunya, Zika and dengue virus infections: The pathogenesis from mother to fetus and the implications of co-infections and vaccine development

Chikungunya (CHIKV), Zika (ZIKV), and Dengue viruses (DENV) exhibit similar epidemiological and clinical patterns but have different pathophysiological mechanisms of disease manifestations. Differences occur in the severity of clinical presentations with the highest mortality in the general population attributed to DENV and neurological morbidity due to ZIKV. ZIKV and DENV infections can cause fetal loss with ZIKV exhibiting teratogenesis. CHIKV is associated with severe complications in the newborn. Co-circulation of the three viruses and the cross-reactive immune response between ZIKV and DENV viruses has implications for an attenuated clinical response and future vaccine development. Co-infections could increase due to the epidemiologic synergy, but there is limited evidence about the clinical effects, especially for the vulnerable newborn. The purpose of this paper is to review the pathophysiological basis for vertically transmission manifestations due to CHIKV, DENV, and ZIKV, to determine the potential effects of co-circulation on newborn outcomes and the potential for vaccine protection. Inflammatory cytokines are responsible for placental breaches in DENV and ZIKV; Hofbauer cells facilitate the transfer of ZIKV from the placenta to the fetal brain, and high viral loads and mechanical placental disruption facilitate the transmission of CHIKV. Co-infection of these viruses can present with severe manifestations, but the clinical and serologic evidence suggests that one virus predominates which may influence fetal transmission. All three viruses are in different stages of vaccine development with DENV vaccine being fully licensed. Antibody-enhanced infections in seronegative vaccinated candidates who develop natural infection to dengue limit its use and have implications for ZIKV vaccine development. Targeting transmission capacity in the vector could prevent transmission to all three viruses, and breast milk immunity could provide further clues for vaccine development.

Pathogen blocking in Wolbachia-infected Aedes aegypti is not affected by Zika and dengue virus co-infection

Background

Wolbachia’s ability to restrict arbovirus transmission makes it a promising tool to combat mosquito-transmitted diseases. Wolbachia-infected Aedes aegypti are currently being released in locations such as Brazil, which regularly experience concurrent outbreaks of different arboviruses. A. aegypti can become co-infected with, and transmit multiple arboviruses with one bite, which can complicate patient diagnosis and treatment.

Methodology/principle findings

Using experimental oral infection of A. aegypti and then RT-qPCR, we examined ZIKV/DENV-1 and ZIKV/DENV-3 co-infection in Wolbachia-infected A. aegypti and observed that Wolbachia-infected mosquitoes experienced lower prevalence of infection and viral load than wildtype mosquitoes, even with an extra infecting virus. Critically, ZIKV/DENV co-infection had no significant impact on Wolbachia’s ability to reduce viral transmission. Wolbachia infection also strongly altered expression levels of key immune genes Defensin C and Transferrin 1, in a virus-dependent manner.

Conclusions/significance

Our results suggest that pathogen interference in Wolbachia-infected A. aegypti is not adversely affected by ZIKV/DENV co-infection, which suggests that Wolbachia-infected A. aegypti will likely prove suitable for controlling mosquito-borne diseases in environments with complex patterns of arbovirus transmission.

Wolbachia is an endosymbiotic bacterium that infects insects. It has been artificially transferred into Aedes aegypti, a mosquito species that can transmit medically important viruses including dengue, chikungunya, and Zika. Wolbachia in A. aegypti limits infection with these viruses, making the mosquitoes much less capable of transmitting them to people. In tropical areas, where these viral pathogens are commonly found, it is not unusual for outbreaks of different viruses to occur at the same time, which can complicate diagnosis and treatment for those afflicted. Mosquitoes with Wolbachia are currently being released into these areas to reduce transmission of these diseases. In our study, we assessed whether Wolbachia infection in A. aegypti mosquitoes could still effectively inhibit the dengue and Zika viruses if the mosquitoes were fed both viruses at the same time. We found that Wolbachia was still very effective at inhibiting the replication of both viruses in the mosquito, and likewise still greatly reduced the chance of transmission of either virus. Our results suggest that Wolbachia-infected mosquitoes should be able to limit infection with more than one virus, should they encounter them in the field.

Arboviral screening of invasive Aedes species in northeastern Turkey: West Nile virus circulation and detection of insect-only viruses

BACKGROUND

The recent reports of Aedes aegypti and Ae. albopictus populations in Turkey, in parallel with the territorial expansion identified in several surrounding countries, have raised concerns about the establishment and re-establishment of these invasive Aedes mosquitoes in Turkey. This cross-sectional study was performed to detect Aedes aegypti and Ae. albopictus in regions of recent incursions, and screen for viral pathogens known to be transmitted elsewhere by these species.

METHODOLOGY

Mosquitoes were collected at several locations in Artvin, Rize and Trabzon provinces of the Black Sea region during 2016-2017, identified morphologically, pooled and analyzed via generic or specific nucleic acid amplification assays. Viruses in positive pools were identified by product sequencing, cell culture inoculation and next generation sequencing (NGS) in selected specimens.

PRINCIPAL FINDINGS

The study group comprised 791 specimens. Aedes albopictus was the most abundant species in all locations (89.6%), followed by Ae. aegypti (7.8%) and Culex pipiens (2.5%). Mosquitoes were screened for viruses in 65 pools where fifteen (23.1%) were reactive. The infecting strains was identified as West Nile virus (WNV) in 5 pools (7.7%) with Ae. albopictus or Cx. pipiens mosquitoes. The obtained WNV sequences phylogenetically grouped with local and global lineage 1 clade 1a viruses. In 4 (6.2%) and 6 (9.2%) pools, respectively, cell fusing agent virus (CFAV) and Aedes flavivirus (AEFV) sequences were characterized. NGS provided a near-complete AEFV genome in a pool of Ae. albopictus. The strain is provisionally called "AEFV-Turkey", and functional analysis of the genome revealed several conserved motifs and regions associated with virus replication. Merida-like virus Turkey (MERDLVT), a recently-described novel rhabdovirus, was also co-detected in a Cx. pipiens pool also positive for WNV.

CONCLUSIONS/SIGNIFICANCE

Invasive Aedes mosquitoes are established in certain locations of northeastern Turkey. Herein we conclusively show the role of these species in WNV circulation in the region. Biosurveillance is imperative to monitor the spread of these species further into Asia Minor and to detect possible introduction of pathogens.

Serologic Tools and Strategies to Support Intervention Trials to Combat Zika Virus Infection and Disease

Zika virus is an emerging mosquito-borne flavivirus that recently caused a large epidemic in Latin America characterized by novel disease phenotypes, including Guillain-Barré syndrome, sexual transmission, and congenital anomalies, such as microcephaly. This epidemic, which was declared an international public health emergency by the World Health Organization, has highlighted shortcomings in our current understanding of, and preparation for, emerging infectious diseases in general, as well as challenges that are specific to Zika virus infection. Vaccine development for Zika virus has been a high priority of the public health response, and several candidates have shown promise in pre-clinical and early phase clinical trials. The optimal selection and implementation of imperfect serologic assays are among the crucial issues that must be addressed in order to advance Zika vaccine development. Here, I review key considerations for how best to incorporate into Zika vaccine trials the existing serologic tools, as well as those on the horizon. Beyond that, this discussion is relevant to other intervention strategies to combat Zika and likely other emerging infectious diseases.

First outbreak of Oropouche Fever reported in a non-endemic western region of the Peruvian Amazon: Molecular diagnosis and clinical characteristics

INTRODUCTION

Oropouche fever is an under-reported and emerging infectious disease caused by Oropouche virus (OROV). Its incidence is under-estimated mainly due to clinical similarities with other endemic arboviral diseases and the lack of specific diagnostic tests. We report the first outbreak of Oropouche fever in a western region of the Peruvian Amazon in Huanuco, Peru.

METHODS

A transversal study was carried out during an outbreak in the western Region of Huanuco, Peru between January and July of 2016. Blood samples of 268 patients with acute febrile syndrome were collected and analyzed for OROV via RT- PCR and genetic sequencing.

RESULTS

Of all 268 patients, 46 (17%) cases tested positive for OROV. The most common symptoms reported were headache with a frequency of 87% (n = 40) followed by myalgia with 76% (n = 35), arthralgia with 65.2% (n = 30), retro-ocular pain 60.8% (n = 28) and hyporexia with 50% (n = 23). Some patients showed a clinical presentation suggestive of severe OROV infection, of which 4.3% (n = 2) had low platelet count, 8.6% (n = 4) had intense abdominal pain, and 2.1% (n = 1) had a presentation with thoracic pain.

CONCLUSION

This study reports an outbreak of OROV in a region where this virus was not previously identified. The disease caused by OROV is an emerging, underdiagnosed infection that requires further research to determine its virulence, pathogenesis, host range and vectors involved in the urban and sylvatic cycles as well as identifying new genotypes to implement sensitive and specific diagnostic tools that can be applied to endemic regions.

P38 and JNK Mitogen-Activated Protein Kinases Interact With Chikungunya Virus Non-structural Protein-2 and Regulate TNF Induction During Viral Infection in Macrophages

Chikungunya virus (CHIKV), a mosquito-borne Alphavirus, is endemic in different parts of the globe. The host macrophages are identified as the major cellular reservoirs of CHIKV during infection and this virus triggers robust TNF production in the host macrophages, which might be a key mediator of virus induced inflammation. However, the molecular mechanism underneath TNF induction is not understood yet. Accordingly, the Raw264.7 cells, a mouse macrophage cell line, were infected with CHIKV to address the above-mentioned question. It was observed that CHIKV induces both p38 and JNK phosphorylation in macrophages in a time-dependent manner and p-p38 inhibitor, SB203580 is effective in reducing infection even at lower concentration as compared to the p-JNK inhibitor, SP600125. However, inhibition of p-p38 and p-JNK decreased CHIKV induced TNF production in the host macrophages. Moreover, CHIKV induced macrophage derived TNF was found to facilitate TCR driven T cell activation. Additionally, it was noticed that the expressions of key transcription factors involved mainly in antiviral responses (p-IRF3) and TNF production (p-c-jun) were induced significantly in the CHIKV infected macrophages as compared to the corresponding mock cells. Further, it was demonstrated that CHIKV mediated TNF production in the macrophages is dependent on p38 and JNK MAPK pathways linking p-c-jun transcription factor. Interestingly, it was found that CHIKV nsP2 interacts with both p-p38 and p-JNK MAPKs in the macrophages. This observation was supported by the in silico protein-protein docking analysis which illustrates the specific amino acids responsible for the nsP2-MAPKs interactions. A strong polar interaction was predicted between Thr-180 (within the phosphorylation lip) of p38 and Gln-273 of nsP2, whereas, no such polar interaction was predicted for the phosphorylation lip of JNK which indicates the differential roles of p-p38 and p-JNK during CHIKV infection in the host macrophages. In summary, for the first time it has been shown that CHIKV triggers robust TNF production in the host macrophages via both p-p38 and p-JNK/p-c-jun pathways and the interaction of viral protein, nsP2 with these MAPKs during infection. Hence, this information might shed light in rationale-based drug designing strategies toward a possible control measure of CHIKV infection in future.

Mosquito biodiversity and mosquito-borne viruses in the United Arab Emirates

Background

In the last 50 years, the United Arab Emirates (UAE) has experienced rapid population growth and urbanization. Urbanization is known to influence biodiversity, and there appears to be a link between the emergence of arboviruses and urban growth. Very little is known about the UAE mosquito species richness and dominant vectors. We performed a mosquito survey comparing peri-urban sites in Dubai and Al Ain to a protected, natural site in Fujairah emirate. We measured mosquito biodiversity and species composition, and screened mosquito pools for common arboviruses to measure arbovirus activity in the region.

Results

We report ten species of mosquitoes from the UAE, with highest species diversity in the natural site, a protected wadi near the eastern coast. The predominant mosquito was Culex perexiguus, and was associated with peri-urban habitats. The site with lowest mosquito species diversity but relatively high species richness was the peri-urban site of Al Ain Zoo, where we identified Bagaza virus and Barkedji virus, two flaviviruses, in pools of Cx. perexiguus.

Conclusions

Decreased mosquito biodiversity was associated with increased levels of urbanization. The predominance of two species at peri-urban sites was related to the availability of their larval habitats. Arboviruses were associated with the presence of a single predominant mosquito species, Cx. perexiguus.

The influence of raw milk exposures on Rift Valley fever virus transmission

Rift Valley fever virus (RVFV) is a zoonotic phlebovirus that can be transmitted to humans or livestock by mosquitoes or through direct contact with contaminated bodily fluids and tissues. Exposure to bodily fluids and tissues varies by types of behaviors engaged for occupational tasks, homestead responsibilities, or use in dietary or therapeutic capacities. While previous studies have included milk exposures in their analyses, their primary focus on livestock exposures has been on animal handling, breeding, and slaughter. We analyzed data from multiple field surveys in Kenya with the aim of associating RVFV infection to raw milk exposures from common animal species. Of those with evidence of prior RVFV infection by serology (n = 267), 77.2% engaged in milking livestock compared to 32.0% for 3,956 co-local seronegative individuals (p < 0.001), and 86.5% of seropositive individuals consumed raw milk compared to 33.4% seronegative individuals (p < 0.001). Individuals who milked and also consumed raw milk had greater odds of RVFV exposure than individuals whose only contact to raw milk was through milking. Increased risks were associated with exposure to milk sourced from cows (p < 0.001), sheep (p < 0.001), and goats (p < 0.001), but not camels (p = 0.98 for consuming, p = 0.21 for milking). Our data suggest that exposure to raw milk may contribute to a significant number of cases of RVFV, especially during outbreaks and in endemic areas, and that some animal species may be associated with a higher risk for RVFV exposure. Livestock trade is regulated to limit RVFV spread from endemic areas, yet further interventions designed to fully understand the risk of RVFV exposure from raw milk are imperative.

The role of co-infection and swarm dynamics in arbovirus transmission

Arthropod-borne viruses (arboviruses) are transmitted by hematophagous insects, primarily mosquitoes. The geographic range and prevalence of mosquito-borne viruses and their vectors has dramatically increased over the last 50 years. As a result, the most medically important arboviurses now co-exist in many regions, resulting in an increased frequency of co-infections in hosts and vectors. In addition to concurrent infections with human pathogens, mosquito-only viruses and/or enzootic viruses not associated with human disease are ubiquitous in mosquito populations. Moreover, mosquito-borne viruses are largely RNA viruses that exist within individual hosts as a diverse and dynamic swarm of closely related genotypes. Interactions among co-infecting viruses and genotypes can have profound effects on virulence, fitness and evolution. Here, we review our understanding of how these complex interactions influence transmission of mosquito-borne viruses, focusing on the often-neglected virus interactions in the mosquito vector, and identify gaps in our knowledge that should guide future studies.

Metabolomic Insights into Human Arboviral Infections: Dengue, Chikungunya, and Zika Viruses

The global burden of arboviral diseases and the limited success in controlling them calls for innovative methods to understand arbovirus infections. Metabolomics has been applied to detect alterations in host physiology during infection. This approach relies on mass spectrometry or nuclear magnetic resonance spectroscopy to evaluate how perturbations in biological systems alter metabolic pathways, allowing for differentiation of closely related conditions. Because viruses heavily depend on host resources and pathways, they present unique challenges for characterizing metabolic changes. Here, we review the literature on metabolomics of arboviruses and focus on the interpretation of identified molecular features. Metabolomics has revealed biomarkers that differentiate disease states and outcomes, and has shown similarities in metabolic alterations caused by different viruses (e.g., lipid metabolism). Researchers investigating such metabolomic alterations aim to better understand host⁻virus dynamics, identify diagnostically useful molecular features, discern perturbed pathways for therapeutics, and guide further biochemical research. This review focuses on lessons derived from metabolomics studies on samples from arbovirus-infected humans.

Metagenomic Analysis Reveals Three Novel and Prevalent Mosquito Viruses from a Single Pool of Aedes vexans nipponii Collected in the Republic of Korea

Arboviruses continue to be a significant global health concern. The unbiased metagenomic analyses of mosquito-borne and mosquito-specific viruses are useful to understand viral diversity and for the surveillance of pathogens of medical and veterinary importance. Metagenomic analysis was conducted on 6368 mosquitoes (736 pools), covering 16 species from 18 locations throughout the Republic of Korea (ROK) in 2016. In this report, we describe three viruses detected in a single pool of Aedes vexans nipponii collected at Yongsan U.S. Army Garrison, located in a densely populated district of Seoul, the ROK. The three novel viruses, designated as Yongsan bunyavirus 1 (YBV1), Yongsan picorna-like virus 3 (YPLV3) and Yongsan sobemo-like virus 1 (YSLV1), share sequence and structural characteristics with members belonging to the family Bunyaviridae, order Picornavirales, and family Solemoviridae, with shared RNA-dependent RNA polymerase (RdRp) amino acid identities of 40%, 42% and 86%, respectively. The real-time reverse transcription and polymerase chain reaction (RT-PCR) of 3493 Aedes vexans nipponii (257 pools) showed a high prevalence of YBV1 and YSLV1 viruses, which were present in 65% and 62% of tested pools, respectively. This study highlighted the utility of a metagenomic sequencing approach for arbovirus discovery and for a better understanding of the virome of potential medically relevant vectors.

The Wolbachia mobilome in Culex pipiens includes a putative plasmid

Wolbachia is a genus of obligate intracellular bacteria found in nematodes and arthropods worldwide, including insect vectors that transmit dengue, West Nile, and Zika viruses. Wolbachia's unique ability to alter host reproductive behavior through its temperate bacteriophage WO has enabled the development of new vector control strategies. However, our understanding of Wolbachia's mobilome beyond its bacteriophages is incomplete. Here, we reconstruct near-complete Wolbachia genomes from individual ovary metagenomes of four wild Culex pipiens mosquitoes captured in France. In addition to viral genes missing from the Wolbachia reference genome, we identify a putative plasmid (pWCP), consisting of a 9.23-kbp circular element with 14 genes. We validate its presence in additional Culex pipiens mosquitoes using PCR, long-read sequencing, and screening of existing metagenomes. The discovery of this previously unrecognized extrachromosomal element opens additional possibilities for genetic manipulation of Wolbachia.

Forecasting the West Nile Virus in the United States: An Extensive Novel Data Streams-Based Time Series Analysis and Structural Equation Modeling of Related Digital Searching Behavior

BACKGROUND

West Nile virus is an arbovirus responsible for an infection that tends to peak during the late summer and early fall. Tools monitoring Web searches are emerging as powerful sources of data, especially concerning infectious diseases such as West Nile virus.

OBJECTIVE

This study aimed at exploring the potential predictive power of West Nile virus-related Web searches.

METHODS

Different novel data streams, including Google Trends, WikiTrends, YouTube, and Google News, were used to extract search trends. Data regarding West Nile virus cases were obtained from the Centers for Disease Control and Prevention. Data were analyzed using regression, times series analysis, structural equation modeling, and clustering analysis.

RESULTS

In the regression analysis, an association between Web searches and "real-world" epidemiological figures was found. The best seasonal autoregressive integrated moving average model with explicative variable (SARIMAX) was found to be (0,1,1)x(0,1,1)4. Using data from 2004 to 2015, we were able to predict data for 2016. From the structural equation modeling, the consumption of West Nile virus-related news fully mediated the relation between Google Trends and the consumption of YouTube videos, as well as the relation between the latter variable and the number of West Nile virus cases. Web searches fully mediated the relation between epidemiological figures and the consumption of YouTube videos, as well as the relation between epidemiological data and the number of accesses to the West Nile virus-related Wikipedia page. In the clustering analysis, the consumption of news was most similar to the Web searches pattern, which was less close to the consumption of YouTube videos and least similar to the behavior of accessing West Nile virus-related Wikipedia pages.

CONCLUSIONS

Our study demonstrated an association between epidemiological data and search patterns related to the West Nile virus. Based on this correlation, further studies are needed to examine the practicality of these findings.

Evaluation of enhanced oviposition attractant formulations against Aedes and Culex vector mosquitoes in urban and semi-urban areas

Surveillance is not only an important tool to assess the population dynamics of vector mosquitoes, but it can also be used to control vector-borne diseases. Mosquito vectors that belong to several genera such as Anopheles, Aedes, and Culex play a crucial role in the transmission of malaria, dengue, chikungunya, Zika, and elephantiasis diseases worldwide. We tested the efficacy of two commercial-grade oviposition attractant formulations that were developed for the container-inhabiting Aedes aegypti, Aedes albopictus, and Culex quinquefasciatus mosquitoes present in urban or semi-urban environments. These attractants can lure gravid females. Field trials were conducted in residential yards during a post-rainy season in September and October. Our data showed considerable efficacy for both attractants. Aedes-attractant collected 1.6-fold more larvae (101.2 ± 10.5 larvae/trap) than the control, and Culex-attractant collected 1.27-fold more larvae (151.2 ± 12.5 larvae/trap) than the control, resulting in 0.8 and 0.7 oviposition attraction indices (OAIs), respectively. Regression analysis indicated that the Aedes-attractant was more stable than the Culex-attractant. Location and time did not alter the efficacy of these attractants. Our experiment suggests that these attractants can be used for the development of species-specific gravid traps to detect, estimate, and control the mosquito population in urban and semi-urban areas.

Evolutionary and ecological insights into the emergence of arthropod-borne viruses

The emergence of arthropod-borne viruses (arboviruses) is of global concern as they can rapidly spread across countries and to new continents as the recent examples of chikungunya virus and Zika virus have demonstrated. Whereas the global movement patterns of emerging arboviruses are comparatively well studied, there is little knowledge on initial emergence processes that enable sylvatic (enzootic) viruses to leave their natural amplification cycle and infect humans or livestock, often also involving infection of anthropophilic vector species. Emerging arboviruses almost exclusively originate in highly biodiverse ecosystems of tropical countries. Changes in host population diversity and density can affect pathogen transmission patterns and are likely to influence arbovirus emergence processes. This review focuses on concepts from disease ecology, explaining the interplay between biodiversity and pathogen emergence.

Monocyte-Derived Dendritic Cells as Model to Evaluate Species Tropism of Mosquito-Borne Flaviviruses

Several mosquito-borne Flaviviruses such as Japanese encephalitis virus (JEV), West Nile virus (WNV), Dengue Virus (DENV), and Zika virus (ZIKV) can cause severe clinical disease. Being zoonotic, Flaviviruses infect a wide variety of terrestrial vertebrates, which dependent of the virus-host interactions, can enhance ongoing epidemics and maintain the virus in the environment for prolonged periods. Targeted species can vary from amphibians, birds to various mammals, dependent on the virus. For many mosquito-borne flaviviruses the spectrum of targeted species is incompletely understood, in particular with respect to their contribution to the maintenance of virus in certain geographical regions. Furthermore, little is known about virus and host factors contributing to species tropism. The present study utilized human and porcine monocyte-derived dendritic cells (MoDC) as a cell culture model to better understand Flavivirus species tropism and innate immune responses. MoDC were selected based on their presence in the skin and their role as an early target cell for several Flaviviruses and their role as immune sentinels. While differences in viral infectivity and replication were minor when comparing porcine with human MoDC for some of the tested Flaviviruses, a particularly strong replication in human MoDC was found with USUV, while JEV appeared to have a stronger tropism for porcine MoDC. With respect to innate immune responses we found high induction of TNF and IFN-β in both human and porcine MoDC after infection with JEV, WNV, and USUV, but not with DENV, ZIKV, and Wesselsbron virus. Spondweni virus induced these cytokine responses only in porcine MoDC. Overall, innate immune responses correlated with early infectivity and cytokine production. In conclusion, we demonstrate Flavivirus-dependent differences in the interaction with MoDC. These may play a role in pathogenesis but appear to only partially reflect the expected species tropism.

Molecular characterization of viruses associated with encephalitis in São Paulo, Brazil

The objective of this study was to characterize the prevalence of viral encephalitis due to arbovirus infection of the Togaviridae and Flaviviridae families in São Paulo, Brazil. A total of 500 cerebrospinal fluid (CSF) samples collected between August 2012 and January 2013, from patients with symptoms of acute encephalitis were analyzed. Findings suggestive of viral encephalitis-elevations in cell concentration, glucose and total protein-were observed in 234 (46.8%) samples, designated as Group 1. The remaining 266 samples comprised Group 2. All samples were tested for Flaviviruses (dengue virus 1, 2, 3 and 4, yellow fever virus and West Nile virus), Alphavirus (NS5 region) and enterovirus by RT- PCR and for herpesviruses and enteroviruses using CLART-Entherpex. A presumptive viral etiological agent was detected in 26 samples (5.2%), 18 (8.0%) in Group 1 and 8 (3.0%) in Group 2. In Group 1 human herpesviruses were detected in 9 cases, enteroviruses in 7 cases, dengue viruses (DENV) in 2 CSFs and St. Louis encephalitis virus (SLEV) in one case. In Group 2 there were 3 CSFs positive for human herpesviruses, 2 for enteroviruses, 2 for DENV and 1 for SLEV. Detection of arboviruses, even though present in a minority of infected patients, identifies these viruses as a probable etiological agent of encephalitis. This is of special concern in regions where this class of viruses is endemic and has been linked to other recent epidemics.

Genetic diversity of the Yokose virus, XYBX1332, isolated from bats (Myotis daubentonii) in China

BACKGROUND

Yokose virus was first isolated from bats (Miniopterus fuliginosus) collected in Yokosuka, Japan, in 1971, and is a new member of the family Flaviviridae, genus Flavivirus. In this study, we isolated a Yokose virus from a serum sample of Myotis daubentonii (order Chiroptera, family Vespertilionidae) collected in Yunnan province, China in 2013.

METHODS

The serum specimens of bat were used to inoculate in BHK-21 and Vero E6 cells for virus isolation. Then the viral complete genome sequence was obtained and was used for phylogenetic analysis performed by BEAST software package.

RESULTS

The virus was shown to have cytopathic effects in mammalian cells (BHK-21 and Vero E6). Genome sequencing indicated that it has a single open reading frame (ORF), with a genome of 10,785 nucleotides in total. Phylogenetic analysis of the viral genome suggests that XYBX1332 is a Yokose virus (YOKV) of the genus Flavivirus. Nucleotide and amino acid homology levels of the ORF of XYBX1332 and Oita-36, the original strain of YOKV, were 72 and 82%, respectively. The ORFs of XYBX1332 and Oita-36 encode 3422 and 3425 amino acids, respectively. In addition, the non-coding regions (5'- and 3'-untranslated regions [UTRs]) of these two strains differ in length and the homology of the 5'- and 3'-UTRs was 81.5 and 78.3%, respectively.

CONCLUSION

The isolation of YOKV (XYBX1332) from inland China thousands of kilometers from Yokosuka, Japan, suggests that the geographical distribution of YOKV is not limited to the islands of Japan and that it can also exist in the inland areas of Asia. However, there are large differences between the Chinese and Japanese YOKV strains in viral genome.

Integrated Mosquito Management: Is Precision Control a Luxury or Necessity?

The versatility of mosquito species that spread emerging arthropod-borne viruses such as Zika has highlighted the urgent need to re-evaluate mosquito-control standards. The prospect of using precise knowledge of the geographic distribution and vector status of local populations to guide targeted interventions has gained renewed attention, but the feasibility and utility of such an approach remain to be investigated. Using the example of mosquito management in the USA, we present ideas for designing, monitoring, and assessing precision vector control tailored to different environmental and epidemiological settings. We emphasize the technical adjustments that could be implemented in mosquito-control districts to enable targeted control while strengthening traditional management.

Islands as Hotspots for Emerging Mosquito-Borne Viruses: A One-Health Perspective

During the past ten years, an increasing number of arbovirus outbreaks have affected tropical islands worldwide. We examined the available literature in peer-reviewed journals, from the second half of the 20th century until 2018, with the aim of gathering an overall picture of the emergence of arboviruses in these islands. In addition, we included information on environmental and social drivers specific to island setting that can facilitate the emergence of outbreaks. Within the context of the One Health approach, our review highlights how the emergence of arboviruses in tropical islands is linked to the complex interplay between their unique ecological settings and to the recent changes in local and global sociodemographic patterns. We also advocate for greater coordination between stakeholders in developing novel prevention and mitigation approaches for an intractable problem.

Arboviruses in South Africa, known and unknown

The emergence of novel arboviruses of zoonotic potential in South Africa (SA) threatens human health and animal welfare, and affects economic growth and development. These viruses cause severe infections in animals and humans, including neurological diseases, such as encephalitis, resulting in high morbidities, mortalities and economic losses. With increasing reports of Middelburg, Shuni, Sindbis, West Nile and Wesselsbron virus infections in animals and humans in SA, this article reviews and discusses known and currently emerging arboviruses in the country. These reports underscore the need for increased surveillance, vector control management, public health preparedness, focused research, community awareness programs, and the development of rapid and sensitive diagnostic approaches. Furthermore, appropriate medical personnel training and strengthening initiatives for a one-health approach are required to understand and mitigate the emerging arboviral threat to public health.

Survey of mosquito-borne flaviviruses in the Cuitzmala River Basin, Mexico: do they circulate in rodents and bats?

BACKGROUND

RNA viruses commonly infect bats and rodents, including mosquito-borne flaviviruses (MBFV) that affect human and animal health. Serological evidence suggests past interactions between these two mammalian orders with dengue viruses (DENV), West Nile virus (WNV), and yellow fever virus (YFV). Although in Mexico there are reports of these viruses in both host groups, we know little about their endemic cycles or persistence in time and space.

METHODS

Rodents and bats were captured at the Cuitzmala River Basin on the Pacific coast of Jalisco state, Mexico, where MBFV, such as DENV, have been reported in both humans and bats. Samples were taken during January, June, and October 2014, at locations adjacent to the river. Tissue samples were collected from both bats and rodents and serum samples from rodents only. Highly sensitive serological and molecular assays were used to search for current and past evidence of viral circulation.

RESULTS

One thousand nine hundred forty-eight individuals were captured belonging to 21 bat and 14 rodent species. Seven hundred sixty-nine liver and 764 spleen samples were analysed by means of a specific molecular protocol used to detect flaviviruses. Additionally, 708 serum samples from rodents were examined in order to demonstrate previous exposure to dengue virus serotype 2 (which circulates in the region). There were no positive results with any diagnostic test.

DISCUSSION

To our knowledge, this is the first survey of rodents and only the second survey of bats from the Pacific Coast of Mexico in a search for MBFV. We obtained negative results from all samples. We validated our laboratory tests with negative and positive controls. Our findings are consistent with other empirical and experimental studies in which these mammalian hosts may not replicate mosquito-borne flaviviruses or present low prevalence.

CONCLUSIONS

True-negative results are essential for the construction of distribution models and are necessary to identify potential areas at risk. Negative results should not be interpreted as the local absence of MBFV in the region. On the contrary, we need to establish a long-term surveillance programme to find MBFV presence in the mosquito trophic networks, identifying the potential role of rodents and bats in viral dynamics.

Essential Oils as Repellents against Arthropods

The development of effective and safe repellents against arthropods is very important, because there are no effective vaccines against arthropod-borne viruses (arboviruses) and parasites. Arboviruses and parasites are transmitted to humans from arthropods, and mosquitoes are the most common arthropods associated with dengue, malaria, and yellow fever. Enormous efforts have been made to develop effective repellents against arthropods, and thus far synthetic repellents have been widely used. However, the use of synthetic repellents has raised several concerns in terms of environmental and human health risks and safety. Thus, plant essential oils (EOs) have been widely used as an alternative to synthetic repellents. In this review, we briefly introduce and summarize recent studies that have investigated EOs as insect repellents. Current technology and research trends to develop effective and safe repellents from plant EOs are also described in this review.