Emerging arboviruses: Why today?

Usefulness of autocidal gravid ovitraps for the surveillance and control of Aedes (Stegomyia) aegypti (Diptera: Culicidae) in eastern Colombia

In the past decade, new strategies have been developed to control the Aedes aegypti (Diptera: Culicidae) mosquito vector, as well as a broad range of arboviral agents. Vector control surveillance programmes in Puerto Rico and Australia have implemented the Centers for Disease Control and Prevention autocidal gravid ovitrap (AGO), which has had an impact on vector density and, consequently, the epidemiology of arboviral infections. Colombia intends to establish the AGO as a new tool for the surveillance and control of the A. aegypti vector. AGOs were evaluated in a hyperendemic area for dengue virus during an 8-week period in Villavicencio city, eastern Colombia. The results indicated that the AGOs detect a high density of A. aegypti, with positive results for these traps of over 80% and an average catch of six individuals per trap per week. Acceptance of AGOs in the community exceeded 95%, and adherence was around 89%. This study's results demonstrate, for the first time in Colombia, that traps are a useful tool for the surveillance of A. aegypti. Future studies must consider the implementation of AGOs in the region.

The Mayaro virus and its potential epidemiological consequences in Colombia: an exploratory biomathematics analysis

Background

Mayaro virus (Togaviridae) is an endemic arbovirus of the Americas with epidemiological similarities with the agents of other more prominent diseases such as dengue (Flaviviridae), Zika (Flaviviridae), and chikungunya (Togaviridae). It is naturally transmitted in a sylvatic/rural cycle by Haemagogus spp., but, potentially, it could be incorporated and transmitted in an urban cycle by Aedes aegypti, a vector widely disseminated in the Americas.

Methods

The Mayaro arbovirus dynamics was simulated mathematically in the colombian population in the eight biogeographical provinces, bearing in mind the vector’s population movement between provinces through passive transport via truck cargo. The parameters involved in the virus epidemiological dynamics, as well as the vital rates of Ae. aegypti in each of the biogeographical provinces were obtained from the literature. These data were included in a meta-population model in differential equations, represented by a model structured by age for the dynamic population of Ae. aegypti combined with an epidemiological SEI/SEIR-type model. In addition, the model was incorporated with a term of migration to represent the connectivity between the biogeographical provinces.

Results

The vital rates and the development cycle of Ae. aegypti varied between provinces, having greater biological potential between 23 °C and 28 °C in provinces of Imerí, biogeographical Chocó, and Magdalena, with respect to the North-Andean Moorland (9.33–21.38 °C). Magdalena and Maracaibo had the highest flow of land cargo. The results of the simulations indicate that Magdalena, Imerí, and biogeographical Chocó would be the most affected regarding the number of cases of people infected by Mayaro virus over time.

Conclusions

The temperature in each of the provinces influences the local population dynamics of Ae. aegypti and passive migration via transport of land cargo plays an important role on how the Mayaro virus would be disseminated in the human population. Once this arbovirus begins an urban cycle, the most-affected departments would be Antioquia, Santander, Norte de Santander, Cesar (Provinces of Magdalena), and Valle del Cauca, and Chocó (biogeographical province of Chocó), which is why vector control programmes must aim their efforts at these departments and include some type of vector control to the transport of land cargo to avoid a future Mayaro epidemic.

Serologic Evidence of Arthropod-Borne Virus Infections in Wild and Captive Ruminants in Ontario, Canada

Arthropod-borne viruses (arboviruses) are globally widespread, and their transmission cycles typically involve numerous vertebrate species. Serologic testing of animal hosts can provide a routine surveillance approach to monitoring animal disease systems, can provide a surveillance alternative to arthropod testing and human case reports, and may augment knowledge of epizootiology. Wild and captive ruminants represent good candidate sentinels to track geographic distribution and prevalence of select arboviruses. They often are geographically widespread and abundant, inhabit areas shared by humans and domestic animals, and are readily fed on by various hematophagous arthropod vectors. Ontario, Canada, is home to high densities of coexisting humans, livestock, and wild cervids, as well as growing numbers of arthropod vectors because of the effects of climate change. We collected blood samples from 349 livestock (cattle/sheep) and 217 cervids (wild/farmed/zoo) in Ontario (2016-2019) to assess for antibodies to zoonotic and agriculturally important arboviruses. Livestock sera were tested for antibodies to bluetongue virus (BTV) and epizootic hemorrhagic disease virus (EHDV). Sera from cervids were tested for antibodies to BTV, EHDV, West Nile virus (WNV), eastern equine encephalitis virus (EEEV), Powassan virus (POWV), and heartland virus (HRTV). Fifteen (9.0%) cattle were seropositive for EHDV-serotype 2. Nine (4.2%) cervids were seropositive for arboviruses; three confirmed as WNV, three as EEEV, and one as POWV. All animals were seronegative for BTV and HRTV. These results reveal low seroprevalence of important agricultural, wildlife, and zoonotic pathogens and underline the need for continued surveillance in this and other regions in the face of changing environmental conditions.

The Absence of Yellow Fever in Asia: History, Hypotheses, Vector Dispersal, Possibility of YF in Asia, and Other Enigmas

Since the recent epidemics of yellow fever in Angola and Brazil as well as the importation of cases to China in 2016, there has been an increased interest in the century-old enigma, absence of yellow fever in Asia. Although this topic has been repeatedly reviewed before, the history of human intervention has never been considered a critical factor. A two-stage literature search online for this review, however, yielded a rich history indispensable for the debate over this medical enigma. As we combat the pandemic of COVID-19 coronavirus worldwide today, we can learn invaluable lessons from the historical events in Asia. In this review, I explore the history first and then critically examine in depth major hypotheses proposed in light of accumulated data, global dispersal of the principal vector, patterns of YF transmission, persistence of urban transmission, and the possibility of YF in Asia. Through this process of re-examination of the current knowledge, the subjects for research that should be conducted are identified. This review also reveals the importance of holistic approach incorporating ecological and human factors for many unresolved subjects, such as the enigma of YF absence in Asia, vector competence, vector dispersal, spillback, viral persistence and transmission mechanisms.

Seroprevalence, spatial dispersion and factors associated with flavivirus and chikungunha infection in a risk area: a population-based seroprevalence study in Brazil

BACKGROUND

The State of Ceará, in Northeastern Brazil, suffers from a triple burden of arboviruses (dengue, Zika and chikungunya). We measured the seroprevalence of chikungunya, dengue and Zika and its associated factors in the population of Juazeiro do Norte, Southern Ceará State, Brazil.

METHODS

A cross-sectional study of analytical and spatial analysis was performed to estimate the seroprevalence of dengue, Zika and chikungunya, in the year 2018. Participants were tested for IgM and IgG against these three viruses. Those with IgM and/or IgG positive tests results were considered positive. Poisson regression was used to analyze the factors associated with positive cases, in the same way that the spatial analysis of positive cases was performed to verify whether the cases were grouped.

RESULTS

Of the 404 participants, 25.0% (103/404) were positive for CHIKV, 92.0% (373/404) for flavivirus (dengue or Zika) and of these, 37.9% (153/404) samples were classified as probable dengue infection. Of those who reported having had an arbovirus in the past, positive CHIKV cases had 58.7% arthralgia (PR = 4.31; 95% CI: 2.06-9.03; p = 0.000) mainly in the hands, ankles and feet. Age over 60 years had a positive association with cases of flavivirus (PR = 1.29; 95% CI: 1.09-1.54; p = 0.000). Fever, muscle pain, joint pain and skin rash were the most reported symptoms (46.1, 41.0, 38.3 and 28.41%, respectively). The positive cases of chikungunya and dengue or Zika were grouped in space and the city center was most affected area.

CONCLUSIONS

Four years after the introduction of CHIKV, where DENV has been in circulation for over 30 years, 1/4 of the population has already been exposed, showing the extent of the epidemic. The measured prevalence was much higher than that reported by local epidemiological surveillance.

Autochthonous circulation of Saint Louis encephalitis and West Nile viruses in the Province of La Rioja, Argentina

St. Louis encephalitis (SLEV) and West Nile (WNV) arboviruses, which circulate in Argentina, are maintained in enzootic transmission cycles involving Culex mosquitoes (vectors) and birds belonging to orders Passeriformes and Columbiformes (amplifier hosts). The objective of this work was to determine the circulation of both viruses among wild birds in a semiarid ecosystem in the Province of La Rioja through a serologic survey. During spring 2013 and fall 2014, a total of 326 wild birds belonging to 41 species were captured in areas close to the cities of La Rioja and Chilecito, in the Province of La Rioja. While exposure to SLEV and WNV was analyzed in birds' serum through neutralizing antibody detection, viral circulation was estimated through apparent seroprevalence of neutralizing antibodies. The exposure of the avian community to viruses was 3.02% for SLEV and 1.89% for WNV, while 1.19% corresponded to coinfections. Our study confirms for the first time the circulation of SLEV and WNV in wild birds in the Province of La Rioja. Moreover, it is the first study to register neutralizing antibodies for flavivirus in the species Leptotila verreauxi (White-tipped Dove) (WNV) and Melanerpes cactorum (White-fronted Woodpecker) (SLEV). These results suggest that in semiarid ecosystems from northwestern Argentina the requirements and conditions for amplification and enzootic maintenance of SLEV and WNV would be present.

Strategies for Assessing Arbovirus Genetic Variability in Vectors and/or Mammals

Animal arboviruses replicate in their invertebrate vectors and vertebrate hosts. They use several strategies to ensure replication/transmission. Their high mutation rates and propensity to generate recombinants and/or genome segment reassortments help them adapt to new hosts/emerge in new geographical areas. Studying arbovirus genetic variability has been used to identify indicators which predict their potential to adapt to new hosts and/or emergence and in particular quasi-species. Multiple studies conducted with insect-borne viruses laid the foundations for the "trade-off" hypothesis (alternation of host transmission cycle constrains arbovirus evolution). It was extrapolated to tick-borne viruses, where too few studies have been conducted, even though humans faced emergence of numerous tick-borne virus during the last decades. There is a paucity of information regarding genetic variability of these viruses. In addition, insects and ticks do not have similar lifecycles/lifestyles. Indeed, tick-borne viruses are longer associated with their vectors due to tick lifespan. The objectives of this review are: (i) to describe the state of the art for all strategies developed to study genetic variability of insect-borne viruses both in vitro and in vivo and potential applications to tick-borne viruses; and (ii) to highlight the specificities of arboviruses and vectors as a complex and diverse system.

The influence of anthropogenic habitat fragmentation on the genetic structure and diversity of the malaria vector Anopheles cruzii (Diptera: Culicidae)

Fragmentation of natural environments as a result of human interference has been associated with a decrease in species richness and increase in abundance of a few species that have adapted to these environments. The Brazilian Atlantic Forest, which has been undergoing an intense process of fragmentation and deforestation caused by human-made changes to the environment, is an important hotspot for malaria transmission. The main vector of simian and human malaria in this biome is the mosquito Anopheles cruzii. Anthropogenic processes reduce the availability of natural resources at the tree canopies, An. cruzii primary habitat. As a consequence, An. cruzii moves to the border of the Atlantic Forest nearing urban areas seeking resources, increasing their contact with humans in the process. We hypothesized that different levels of anthropogenic changes to the environment can be an important factor in driving the genetic structure and diversity in An. cruzii populations. Five different hypotheses using a cross-sectional and a longitudinal design were tested to assess genetic structure in sympatric An. cruzii populations and microevolutionary processes driving these populations. Single nucleotide polymorphisms were used to assess microgeographic genetic structure in An. cruzii populations in a low-endemicity area in the city of São Paulo, Brazil. Our results show an overall weak genetic structure among the populations, indicating a high gene flow system. However, our results also pointed to the presence of significant genetic structure between sympatric An. cruzii populations collected at ground and tree-canopy habitats in the urban environment and higher genetic variation in the ground-level population. This indicates that anthropogenic modifications leading to habitat fragmentation and a higher genetic diversity and structure in ground-level populations could be driving the behavior of An. cruzii, ultimately increasing its contact with humans. Understanding how anthropogenic changes in natural areas affect An. cruzii is essential for the development of more effective mosquito control strategies and, on a broader scale, for malaria-elimination efforts in the Brazilian Atlantic Forest.

High Seroprevalence of Antibodies against Arboviruses among Pregnant Women in Rural Caribbean Colombia in the Context of the Zika Virus Epidemic

Mosquito-borne viruses such as dengue (DENV), chikungunya (CHIKV), and Zika (ZIKV) have spread in recent decades. We aimed to assess seroprevalence of arboviral infections in pregnant women living in Cereté, Caribbean Colombia. In 2016 a cross-sectional facility-based sero-survey study was performed among pregnant women (N = 90). Most of them (66%) reported at least one symptom or sign compatible with arboviral infection over the previous 15 days. All screened women had a positive IgG for DENV, 89% for ZIKV, and 82% for CHIKV. One woman tested positive for ZIKV IgM. This study shows the high exposure among pregnant women to arboviruses in endemic areas, shown by the high seroprevalence of past arboviral infections. Given the evidence on the potential risks of these arboviral infections on pregnancy and infant outcomes, these results highlight the need for continuous epidemiological surveillance of arboviral diseases, particularly among those most of risk of their harmful consequences.

A Sensitive, Rapid, and Portable CasRx-based Diagnostic Assay for SARS-CoV-2

Since its first emergence from China in late 2019, the SARS-CoV-2 virus has spread globally despite unprecedented containment efforts, resulting in a catastrophic worldwide pandemic. Successful identification and isolation of infected individuals can drastically curtail virus spread and limit outbreaks. However, during the early stages of global transmission, point-of-care diagnostics were largely unavailable and continue to remain difficult to procure, greatly inhibiting public health efforts to mitigate spread. Furthermore, the most prevalent testing kits rely on reagent- and time-intensive protocols to detect viral RNA, preventing rapid and cost-effective diagnosis. Therefore the development of an extensive toolkit for point-of-care diagnostics that is expeditiously adaptable to new emerging pathogens is of critical public health importance. Recently, a number of novel CRISPR-based diagnostics have been developed to detect COVID-19. Herein, we outline the development of a CRISPR-based nucleic acid molecular diagnostic utilizing a Cas13d ribonuclease derived from Ruminococcus flavefaciens (CasRx) to detect SARS-CoV-2, an approach we term SENSR (Sensitive Enzymatic Nucleic-acid Sequence Reporter). We demonstrate SENSR robustly detects SARS-CoV-2 sequences in both synthetic and patient-derived samples by lateral flow and fluorescence, thus expanding the available point-of-care diagnostics to combat current and future pandemics.

Modeling the potential of wAu-Wolbachia strain invasion in mosquitoes to control Aedes-borne arboviral infections

Arboviral infections such as dengue, Zika and chikungunya are fast spreading diseases that pose significant health problems globally. In order to control these infections, an intracellular bacterium called Wolbachia has been introduced into wild-type mosquito populations in the hopes of replacing the vector transmitting agent, Aedes aegypti with one that is incapable of transmission. In this study, we developed a Wolbachia transmission model for the novel wAu strain which possesses several favourable traits (e.g., enhanced viral blockage and maintenance at higher temperature) but not cyctoplasmic incompatibility (CI)-when a Wolbachia-infected male mosquito mates with an uninfected female mosquito, producing no viable offspring. This model describes the competitive dynamics between wAu-Wolbachia-infected and uninfected mosquitoes and the role of imperfect maternal transmission. By analysing the system via computing the basic reproduction number(s) and stability properties, the potential of the wAu strain as a viable strategy to control arboviral infections is established. The results of this work show that enhanced maintenance of Wolbachia infection at higher temperatures can overcome the lack of CI induction to support wAu-Wolbachia infected mosquito invasion. This study will support future arboviral control programs, that rely on the introduction of new Wolbachia variants.

The Role of Temperature in Shaping Mosquito-Borne Viruses Transmission

Mosquito-borne diseases having the greatest impact on human health are typically prevalent in the tropical belt of the world. However, these diseases are conquering temperate regions, raising the question of the role of temperature on their dynamics and expansion. Temperature is one of the most significant abiotic factors affecting, in many ways, insect vectors and the pathogens they transmit. Here, we debate the veracity of this claim by synthesizing current knowledge on the effects of temperature on arboviruses and their vectors, as well as the outcome of their interactions.

Review of Phytochemical Compounds as Antiviral Agents Against Arboviruses from the Genera Flavivirus and Alphavirus

Arboviruses are a diverse group of viruses that are among the major causes of emerging infectious diseases. Arboviruses from the genera flavivirus and alphavirus are the most important human arboviruses from a public health perspective. During recent decades, these viruses have been responsible for millions of infections and deaths around the world. Over the past few years, several investigations have been carried out to identify antiviral agents to treat these arbovirus infections. The use of synthetic antiviral compounds is often unsatisfactory since they may raise the risk of viral mutation; they are costly and possess either side effects or toxicity. One attractive strategy is the use of plants as promising sources of novel antiviral compounds that present significant inhibitory effects on these viruses. In this review, we describe advances in the exploitation of compounds and extracts from natural sources that target the vital proteins and enzymes involved in arbovirus replication.

Genotype-specific neutralizing antibody titers against Japanese encephalitis virus genotypes 1 and 3 in horses immunized with a genotype 3 vaccine

Purpose

Japanese encephalitis is one of the most important mosquito-borne and zoonotic diseases in Asia and the Pacific region. Although the dominant Japanese encephalitis virus (JEV) genotype has shifted from G3 to G1 in Korea since 1990, a G3 strain (Anyang 300) has been used in vaccines for horses for almost 40 years. This study aimed to investigate the seroconversion rates and geometric mean titers (GMTs) of virus-neutralizing antibodies (VNAs) against JEV G1 and G3 in horses immunized with the G3 vaccine.

Materials and Methods

Serum samples of 1,231 horses immunized with the Anyang 300 vaccine were collected in 2018. VNA titers against JEV KV1899 (G1) and Anyang 300 (G3) were measured in all serum samples using the virus neutralization test. Titers were analyzed according to blood sampling time (prior to and following annual revaccination), age, and region.

Results

Rates of VNA titer >10 were 45.1% and 77.8% for G1, and 49.1% and 82.9% for G3 in samples taken before and after revaccination, respectively. GMTs of genotype-specific VNAs against JEV G1 and G3 were 8.3 and 11.6 before revaccination and rose to 27.2 and 65.4 following revaccination. Overall sero-positivity did not significantly differ between genotypes, but GMTs significantly differed among genotypes and sampling times. No significant difference was found in GMTs among age groups or regions.

Conclusion

Genotype-specific neutralizing antibody titers against JEV G1 and G3 differed significantly in horses immunized with the G3 vaccine. Antigenic differences between genotypes could reduce the vaccine's efficacy, requiring the development of a new vaccine.

Examining the Role of Niemann-Pick C1 Protein in the Permissiveness of Aedes Mosquitoes to Filoviruses

Aedes mosquitoes vector many viruses with divergent characteristics, yet the criteria needed for a virus to be vectored by an arthropod remain unknown. The intracellular cholesterol transporter protein Niemann-Pick C1 (NPC1) has been identified as the necessary entry receptor for filoviruses such as Ebola and Marburg viruses. While homologues of NPC1 are observed in mosquitoes, currently no filovirus has been identified as circulating in mosquitoes. This work aimed at increasing the understanding of the mosquito vector by examining the capability of a virus to gain the ability to enter mosquito cells. We developed a model system of Aedes cells expressing human NPC1 (hNPC1) and attempted to infect these cells with recombinant vesicular stomatitis virus expressing the Ebola virus glycoprotein. As compared to the control cells, no significant increase in infection was observed in cells expressing hNPC1, demonstrating that the expression of human NPC1 alone is not sufficient to support filovirus infection, and that host factors other than NPC1 determine filovirus susceptibility of mosquito cells.

From the threat to the large outbreak: dengue on Reunion Island, 2015 to 2018

Background

With more than 300 million infections estimated annually worldwide, dengue is the most prevalent arboviral infection. On Reunion Island, after a large outbreak in 1977–78, only limited episodes of viral circulation or sporadic cases were reported till 2015.

Aim

Our objective was to document and report on the circulation of dengue virus after the occurrence of a small outbreak during austral summer 2015/16 and until the large outbreak of 2018.

Methods

Beside the mandatory notification of biologically confirmed dengue cases, additional systems of surveillance were set up: estimation of dengue-like syndrome in people seeking care by their family doctor, surveillance of emergency department visits related to dengue, surveillance of hospitalised dengue patients and deaths classifications.

Results

After a moderate outbreak during summer 2015/16 with 231 cases, 2017 was characterised by limited viral circulation (97 cases) which, however, persisted during the austral winter. By February 2018, the number of cases had increased and led to a peak at the beginning of May 2018. More than 6,000 cases were reported this year (dengue virus type 2 only). In addition, six deaths of dengue patients were notified.

Conclusion

In 2017, the persistence of transmission during winter created favourable conditions for the emergence of an epidemic during summer 2018. After this moderate epidemic wave, the viral circulation persisted during winter 2018 for the second year, opening the door for the second wave in 2019 and for potential endemisation of the disease on Reunion Island in the near future.

Aedes Mosquito Salivary Components and Their Effect on the Immune Response to Arboviruses

Vector-borne diseases are responsible for over a billion infections each year and nearly one million deaths. Mosquito-borne dengue virus, West Nile, Japanese encephalitis, Zika, Chikungunya, and Rift Valley Fever viruses constitute major public health problems in regions with high densities of arthropod vectors. During the initial step of the transmission cycle, vector, host, and virus converge at the bite site, where local immune cells interact with the vector's saliva. Hematophagous mosquito saliva is a mixture of bioactive components known to modulate vertebrate hemostasis, immunity, and inflammation during the insect's feeding process. The capacity of mosquito saliva to modulate the host immune response has been well-studied over the last few decades and has led to the consensus that the presence of saliva is linked to the enhancement of virus transmission, host susceptibility, disease progression, viremia levels, and mortality. We review some of the major aspects of the interactions between mosquito saliva and the host immune response that may be useful for future studies on the control of arboviruses.

Epidemic Alphaviruses: Ecology, Emergence and Outbreaks

Over the past century, the emergence/reemergence of arthropod-borne zoonotic agents has been a growing public health concern. In particular, agents from the genus Alphavirus pose a significant risk to both animal and human health. Human alphaviral disease presents with either arthritogenic or encephalitic manifestations and is associated with significant morbidity and/or mortality. Unfortunately, there are presently no vaccines or antiviral measures approved for human use. The present review examines the ecology, epidemiology, disease, past outbreaks, and potential to cause contemporary outbreaks for several alphavirus pathogens.

Dengue: A Minireview

Dengue, caused by infection of any of four dengue virus serotypes (DENV-1 to DENV-4), is a mosquito-borne disease of major public health concern associated with significant morbidity, mortality, and economic cost, particularly in developing countries. Dengue incidence has increased 30-fold in the last 50 years and over 50% of the world’s population, in more than 100 countries, live in areas at risk of DENV infection. We reviews DENV biology, epidemiology, transmission dynamics including circulating serotypes and genotypes, the immune response, the pathogenesis of the disease as well as updated diagnostic methods, treatments, vector control and vaccine developments.

A survey of RNA viruses in mosquitoes from Mozambique reveals novel genetic lineages of flaviviruses and phenuiviruses, as well as frequent flavivirus-like viral DNA forms in Mansonia

BACKGROUND

Mosquito-borne diseases involving arboviruses represent expanding threats to sub-Saharan Africa imposing as considerable burden to human and veterinary public health. In Mozambique over one hundred species of potential arbovirus mosquito vectors have been identified, although their precise role in maintaining such viruses in circulation in the country remains to be elucidated. The aim of this study was to screen for the presence of flaviviruses, alphaviruses and bunyaviruses in mosquitoes from different regions of Mozambique.

RESULTS

Our survey analyzed 14,519 mosquitoes, and the results obtained revealed genetically distinct insect-specific flaviviruses, detected in multiple species of mosquitoes from different genera. In addition, smaller flavivirus-like NS5 sequences, frequently detected in Mansonia seemed to correspond to defective viral sequences, present as viral DNA forms. Furthermore, three lineages of putative members of the Phenuiviridae family were also detected, two of which apparently corresponding to novel viral genetic lineages.

CONCLUSION

This study reports for the first-time novel insect-specific flaviviruses and novel phenuiviruses, as well as frequent flavivirus-like viral DNA forms in several widely known vector species. This unique work represents recent investigation of virus screening conducted in mosquitoes from Mozambique and an important contribution to inform the establishment of a vector control program for arbovirus in the country and in the region.

A micro-PRNT for the detection of Ross River virus antibodies in mosquito blood meals: A useful tool for inferring transmission pathways

Introduction

Many arboviruses of public health significance are maintained in zoonotic cycles with complex transmission pathways. The presence of serum antibody against arboviruses in vertebrates provides evidence of their historical exposure but reveals nothing about the vector-reservoir relationship. Moreover, collecting blood or tissue samples from vertebrate hosts is ethically and logistically challenging. We developed a novel approach for screening the immune status of vertebrates against Ross River virus that allows us to implicate the vectors that form the transmission pathways for this commonly notified Australian arboviral disease.

Methods

A micro-plaque reduction neutralisation test (micro-PRNT) was developed and validated on koala (Phascolarctos cinereus) sera against a standard PRNT. The ability of the micro-PRNT to detect RRV antibodies in mosquito blood meals was then tested using two mosquito models. Laboratory-reared Aedes aegypti were fed, via a membrane, on sheep blood supplemented with RRV seropositive and seronegative human sera. Aedes notoscriptus were fed on RRV seropositive and seronegative human volunteers. Blood-fed mosquitoes were harvested at various time points after feeding and their blood meals analysed for the presence of RRV neutralising antibodies using the micro-PRNT.

Results

There was significant agreement of the plaque neutralisation resulting from the micro-PRNT and standard PRNT techniques (R² = 0.65; P<0.0001) when applied to RRV antibody detection in koala sera. Sensitivity and specificity of the micro-PRNT assay were 88.2% and 96%, respectively, in comparison with the standard PRNT. Blood meals from mosquitoes fed on sheep blood supplemented with RRV antibodies, and on blood from RRV seropositive humans neutralised the virus by ≥50% until 48 hr post feeding. The vertebrate origin of the blood meal was also ascertained for the same samples, in parallel, using established molecular techniques.

Conclusions

The small volumes of blood present in mosquito abdomens can be used to identify RRV antibodies and therefore host exposure to arbovirus infection. In tandem with the accurate identification of the mosquito, and diagnostics for the host origin of the blood meal, this technique has tremendous potential for exploring RRV transmission pathways. It can be adapted for similar studies on other mosquito borne zoonoses.

Geographical Genetic Variation and Sources of Korean Aedes albopictus (Diptera: Culicidae) Populations

Aedes albopictus (Skuse, 1894) is a mosquito vector raising global health concerns owing to its transmission of dengue, Zika, and chikungunya viruses. This vector accounts for a large proportion of the Korean mosquito community; however, autochthonous clinical cases resulting from this species remain unreported in South Korea. This study aimed to examine the geographical genetic variations and sources of Ae. albopictus populations in South Korea exclusively on the basis of COI gene analysis from 292 samples collected from 37 localities in 2016-2018 and 290 reference sequences from GenBank. Thirty-eight haplotypes were identified among the 292 Ae. albopictus samples, with H1 (n = 190, 65.1%), H29 (n = 24, 8.22%), and H32 (n = 24, 8.22%) being the most common and widely distributed haplotypes in the mainland, southern coastal region, and Jeju Island, respectively. In general, high haplotype (≥0.5; 44.7%) and low nucleotide (≤0.00148 max.) diversity were observed in these populations. Based on eight regional groups, results of neutral tests and a mismatch analysis supported demographic expansions after bottlenecks. Furthermore, analysis of molecular variance, FST, and K2P distance showed that Gyeongsangnam-do, Jeju Island, and mainland groups were genetically differentiated. Haplotype network and phylogenetic analyses revealed that the sources of the main haplotypes are related to strains from other countries. The current findings need to be validated with additional sampling from heterogeneous habitats and different genetic markers. However, our results suggest that haplotype changes should be closely monitored for efficient vector surveillance and control.

The Emergence of Chikungunya ECSA Lineage in a Mayaro Endemic Region on the Southern Border of the Amazon Forest

Anthropic changes on the edges of the tropical forests may facilitate the emergence of new viruses from the sylvatic environment and the simultaneous circulation of sylvatic and urban viruses in the human population. In this study, we investigated the presence of arboviruses (arthropod-borne viruses) in the sera of 354 patients, sampled from February 2014 to October 2018 in Sinop city. We sequenced the complete genomes of one chikungunya virus (CHIKV)-positive and one out of the 33 Mayaro virus (MAYV)-positive samples. The CHIKV genome obtained here belongs to the East/Central/South African (ECSA) genotype and the MAYV genome belongs to the L genotype. These genomes clustered with other viral strains from different Brazilian states, but the CHIKV strain circulating in Sinop did not cluster with other genomes from the Mato Grosso state, suggesting that at least two independent introductions of this virus occurred in Mato Grosso. Interestingly, the arrival of CHIKV in Sinop seems to not have caused a surge in human cases in the following years, as observed in the rest of the state, suggesting that cross immunity from MAYV infection might be protecting the population from CHIKV infection. These findings reinforce the need for continued genomic surveillance in order to evaluate how simultaneously circulating alphaviruses infecting the human population will unfold.

Antiviral Natural Products for Arbovirus Infections

Over the course of the last 50 years, the emergence of several arboviruses have resulted in countless outbreaks globally. With a high proportion of infections occurring in tropical and subtropical regions where arthropods tend to be abundant, Asia in particular is a region that is heavily affected by arboviral diseases caused by dengue, Japanese encephalitis, West Nile, Zika, and chikungunya viruses. Major gaps in protection against the most significant emerging arboviruses remains as there are currently no antivirals available, and vaccines are only available for some. A potential source of antiviral compounds could be discovered in natural products—such as vegetables, fruits, flowers, herbal plants, marine organisms and microorganisms—from which various compounds have been documented to exhibit antiviral activities and are expected to have good tolerability and minimal side effects. Polyphenols and plant extracts have been extensively studied for their antiviral properties against arboviruses and have demonstrated promising results. With an abundance of natural products to screen for new antiviral compounds, it is highly optimistic that natural products will continue to play an important role in contributing to antiviral drug development and in reducing the global infection burden of arboviruses.

Arboviruses and Muscle Disorders: From Disease to Cell Biology

Infections due to arboviruses (arthropod-borne viruses) have dramatically increased worldwide during the last few years. In humans, symptoms associated with acute infection of most arboviruses are often described as "dengue-like syndrome", including fever, rash, conjunctivitis, arthralgia, and muscular symptoms such as myalgia, myositis, or rhabdomyolysis. In some cases, muscular symptoms may persist over months, especially following flavivirus and alphavirus infections. However, in humans the cellular targets of infection in muscle have been rarely identified. Animal models provide insights to elucidate pathological mechanisms through studying viral tropism, viral-induced inflammation, or potential viral persistence in the muscle compartment. The tropism of arboviruses for muscle cells as well as the viral-induced cytopathic effect and cellular alterations can be confirmed in vitro using cellular models. This review describes the link between muscle alterations and arbovirus infection, and the underlying mechanisms.

Vaccine Advances against Venezuelan, Eastern, and Western Equine Encephalitis Viruses

Vaccinations are a crucial intervention in combating infectious diseases. The three neurotropic Alphaviruses, Eastern (EEEV), Venezuelan (VEEV), and Western (WEEV) equine encephalitis viruses, are pathogens of interest for animal health, public health, and biological defense. In both equines and humans, these viruses can cause febrile illness that may progress to encephalitis. Currently, there are no licensed treatments or vaccines available for these viruses in humans. Experimental vaccines have shown variable efficacy and may cause severe adverse effects. Here, we outline recent strategies used to generate vaccines against EEEV, VEEV, and WEEV with an emphasis on virus-vectored and plasmid DNA delivery. Despite candidate vaccines protecting against one of the three viruses, few studies have demonstrated an effective trivalent vaccine. We evaluated the potential of published vaccines to generate cross-reactive protective responses by comparing DNA vaccine sequences to a set of EEEV, VEEV, and WEEV genomes and determining the vaccine coverages of potential epitopes. Finally, we discuss future directions in the development of vaccines to combat EEEV, VEEV, and WEEV.

Patterns of insecticide resistance in Aedes aegypti: meta-analyses of surveys in Latin America and the Caribbean

BACKGROUND

The re-emergence of worldwide concern with arthropod-borne viruses (arboviruses) draws increasing attention to their mosquito vectors, particularly Aedes aegypti, whose control heavily rely on insecticide use. As a consequence, insecticide resistance is frequent, but the general patterns of occurrence, cross-resistance and prevailing mechanisms remain unrecognized in some areas such as the Neotropical region. Thus, we sought here to recognize the general trends and patterns of insecticide resistance in Latin America and the Caribbean. A systematic literature review (2008-2018) aimed the data-gathering for the region and meta-analyses to address the stated knowledge gap.

RESULTS

A high incidence of insecticide resistance prevails in the mosquito populations of the region. Dichlorodiphenyltrichloroethane (DDT), temephos and deltamethrin were the main insecticides evaluated and the meta-analyses indicate a high frequency of DDT-resistant populations (86.7 ± 0.1%), followed by temephos (75.7 ± 0.1%) and deltamethrin (33.0 ± 0.1%). No evidence of cross-resistance was detected among these three insecticides, and the V1016I knockdown (KDR) site mutation does not explain the patterns of deltamethrin resistance in the region.

CONCLUSION

Resistance to DDT, temephos and deltamethrin is serious and widespread, and there is no cross-resistance among them. Altered target site sensitivity is not the main pyrethroid resistance mechanism, which is likely due to a mix of mechanisms. Therefore, the replacement of deltamethrin and particularly temephos in the region by alternative insecticides is an important resistance management recommendation, but should be done with compounds out of the cross-resistance spectrum for these populations and insecticides. Nonetheless, the non-recognition of the prevalent resistance mechanisms in the region makes this suggestion more difficult to apply and invites more broad-scale studies of resistance mechanisms to fill this knowledge gap and improve the resistance management recommendations. © 2020 Society of Chemical Industry.

Context-Dependent Accuracy of the BG-Counter Remote Mosquito Surveillance Device in North Carolina

There is a clear need for improved vector surveillance approaches that are affordable, labor efficient, and safer than traditional methods. The BG-Counter (Biogents USA, Moorefield, WV) is a device for remotely monitoring mosquito activity in combination with the BG-Sentinel (Biogents USA), a widely used trap for the collection of host-seeking mosquitoes. The BG-Counter uses a wireless connection to provide real-time counts of mosquitoes captured by the BG-Sentinel, allowing users to remotely monitor mosquito populations. This study tested the effectiveness of the BG-Counter in 5 North Carolina counties. A total of 96 trap-days resulted in the collection of >45,000 individual mosquitoes representing 35 species. Aedes albopictus was the most common species collected in all counties, except for New Hanover County where Culex nigripalpus was the most common. The mean daily accuracy ranged from 80.1% (New Hanover County) to 9.4% (Jackson County). There was a significant linear relationship between the actual number of mosquitoes collected and the device counts at all sites except Jackson County, the site with the lowest relative mosquito abundance compared with nontarget organisms. A linear regression of daily BG-Counter accuracy and the daily proportion of mosquitoes to the total number of arthropods collected revealed a significant positive linear relationship, supporting the premise that the BG-Counter is less effective when the relative abundance of mosquitoes is low. Mosquito surveillance programs using the BG-Counter should recognize its context-dependent accuracy and routinely evaluate the accuracy of the device based on local conditions.

Spatial Assessment of Contact Between Humans and Anopheles and Aedes Mosquitoes in a Medium-Sized African Urban Setting, Using Salivary Antibody-Based Biomarkers

BACKGROUND

Anarchic and poorly controlled urbanization led to an increased risk of mosquito-borne diseases (MBD) in many African cities. Here, we evaluate the spatial heterogeneity of human exposure to malaria and arboviral disease vectors in an urban area of northern Senegal, using antibody-based biomarkers of exposure to Anopheles and Aedes mosquito bites.

METHODS

A cross-sectional study was undertaken during the rainy season of 2014 in 4 neighborhoods of Saint-Louis, a city in northern Senegal. Among children aged 6-59 months in each neighborhood, the dried blood spot technique was used to evaluate immunoglobulin G (IgG) responses to both gSG6-P1 (Anopheles) and Nterm-34-kDa (Aedes) salivary peptides as validated biomarkers of respective mosquito bite exposure.

RESULTS

IgG response levels to gSG6-P1 and Nterm-34-kDa salivary peptides varied significantly between the 4 neighborhoods (P < .0001). The level of exposure to Aedes bites also varied according to household access to sanitation services (P = .027), whereas that of exposure to Anopheles bites varied according to insecticide-treated bed net use (P = .006). In addition, spatial clusters of high contact between humans and mosquitoes were identified inside 3 neighborhoods.

CONCLUSIONS

Antibody-based biomarkers of exposure to Anopheles and Aedes mosquito bites could be helpful tools for evaluating the heterogeneity of exposure to malaria and arboviral disease vectors by national control programs.

A Review: Wolbachia-Based Population Replacement for Mosquito Control Shares Common Points with Genetically Modified Control Approaches

The growing expansion of mosquito vectors has made mosquito-borne arboviral diseases a global threat to public health, and the lack of licensed vaccines and treatments highlight the urgent need for efficient mosquito vector control. Compared to genetically modified control strategies, the intracellular bacterium Wolbachia, endowing a pathogen-blocking phenotype, is considered an environmentally friendly strategy to replace the target population for controlling arboviral diseases. However, the incomplete knowledge regarding the pathogen-blocking mechanism weakens the reliability of a Wolbachia-based population replacement strategy. Wolbachia infections are also vulnerable to environmental factors, temperature, and host diet, affecting their densities in mosquitoes and thus the virus-blocking phenotype. Here, we review the properties of the Wolbachia strategy as an approach to control mosquito populations in comparison with genetically modified control methods. Both strategies tend to limit arbovirus infections but increase the risk of selecting arbovirus escape mutants, rendering these strategies less reliable.

Habitat and Seasonality Affect Mosquito Community Composition in the West Region of Cameroon

To identify potential sylvatic, urban and bridge-vectors that can be involved in current or future virus spillover from wild to more urbanised areas, entomological field surveys were conducted in rural, peri-urban and urban areas spanning the rainy and dry seasons in western Cameroon. A total of 2650 mosquitoes belonging to 37 species and eight genera were collected. Mosquito species richness was significantly influenced by the specific combination of the habitat type and the season. The highest species richness was found in the peri-urban area (S = 30, Chao1 = 121 ± 50.63, ACE = 51.97 ± 3.88) during the dry season (S = 28, Chao1 = 64 ± 25.7, ACE = 38.33 ± 3.1). Aedes (Ae.) africanus and Culex (Cx.) moucheti were only found in the rural and peri-urban areas, while Cx. pipiens s.l. and Ae. aegypti were only found in the urban area. Cx. (Culiciomyia) spp., Cx. duttoni and Ae. albopictus were caught in the three habitat types. Importantly, approximately 52% of the mosquito species collected in this study have been implicated in the transmission of diverse arboviruses. This entomological survey provides a catalogue of the different mosquito species that may be involved in the transmission of arboviruses. Further investigations are needed to study the vectorial capacity of each mosquito species in arbovirus transmission.

Human Type I Interferon Antiviral Effects in Respiratory and Reemerging Viral Infections

Type I interferons (IFN-I) are a group of related proteins that help regulate the activity of the immune system and play a key role in host defense against viral infections. Upon infection, the IFN-I are rapidly secreted and induce a wide range of effects that not only act upon innate immune cells but also modulate the adaptive immune system. While IFN-I and many IFN stimulated genes are well-known for their protective antiviral role, recent studies have associated them with potential pathogenic functions. In this review, we summarize the current knowledge regarding the complex effects of human IFN-I responses in respiratory as well as reemerging flavivirus infections of public health significance and the molecular mechanisms by which viral proteins antagonize the establishment of an antiviral host defense. Antiviral effects and immune modulation of IFN-stimulated genes is discussed in resisting and controlling pathogens. Understanding the mechanisms of these processes will be crucial in determining how viral replication can be effectively controlled and in developing safe and effective vaccines and novel therapeutic strategies.

Nano-emulsification Enhances the Larvicidal Potential of the Essential Oil of Siparuna guianensis (Laurales: Siparunaceae) Against Aedes (Stegomyia) aegypti (Diptera: Culicidae)

Siparuna guianensis (Laurales: Siparunaceae) has a terpene-rich essential oil with great potential for larvicides. The poor water miscibility of their compounds makes nano-emulsions of great interest for novel bioactive systems, including for control of Aedes aegypti (Diptera: Culicidae). This species is adapted to urban environments with important role in the epidemiology of some arboviruses such as dengue, chikungunya fever, zika, and urban yellow fever. The aim of the present study was to evaluate the feasibility of nano-emulsification to affect Ae. aegypti larvae. An optimal system was achieved by using a nonionic single surfactant, highlighted by its satisfactory size distribution profile. Moreover, improved larvicidal activity in comparison to bulk essential oil can be observed for the nano-emulsions. The estimated LC50 and LC90 values after 24 h of treatment of larvae with the essential oil were, respectively, 86.5232 and 134.814 µg/ml, while the estimated LC50 and LC90 value after treatment with the nano-emulsion were 24.7572 and 75.2452 µg/ml, respectively. The utilization of a simple technique to produce a fine nano-emulsion opens perspective for further integrative practices of mosquito control and giving value to this Amazon plant species may encourage its sustainable use and contribute to conservation policies.

Multimeric single-domain antibody complexes protect against bunyavirus infections

The World Health Organization has included three bunyaviruses posing an increasing threat to human health on the Blueprint list of viruses likely to cause major epidemics and for which no, or insufficient countermeasures exist. Here, we describe a broadly applicable strategy, based on llama-derived single-domain antibodies (VHHs), for the development of bunyavirus biotherapeutics. The method was validated using the zoonotic Rift Valley fever virus (RVFV) and Schmallenberg virus (SBV), an emerging pathogen of ruminants, as model pathogens. VHH building blocks were assembled into highly potent neutralizing complexes using bacterial superglue technology. The multimeric complexes were shown to reduce and prevent virus-induced morbidity and mortality in mice upon prophylactic administration. Bispecific molecules engineered to present two different VHHs fused to an Fc domain were further shown to be effective upon therapeutic administration. The presented VHH-based technology holds great promise for the development of bunyavirus antiviral therapies.

High Rate of Non-Human Feeding by Aedes aegypti Reduces Zika Virus Transmission in South Texas

Mosquito-borne viruses are emerging or re-emerging globally, afflicting millions of people around the world. Aedes aegypti, the yellow fever mosquito, is the principal vector of dengue, Zika, and chikungunya viruses, and has well-established populations across tropical and subtropical urban areas of the Americas, including the southern United States. While intense arboviral epidemics have occurred in Mexico and further south in the Americas, local transmission in the United States has been minimal. Here, we study Ae. aegypti and Culex quinquefasciatus host feeding patterns and vertebrate host communities in residential environments of South Texas to identify host-utilization relative to availability. Only 31% of Ae. aegypti blood meals were derived from humans, while 50% were from dogs and 19% from other wild and domestic animals. In Cx. quinquefasciatus, 67% of blood meals were derived from chicken, 22% came from dogs, 9% from various wild avian species, and 2% from other mammals including one human, one cat, and one pig. We developed a model for the reproductive number, R0, for Zika virus (ZIKV) in South Texas relative to northern Mexico using human disease data from Tamaulipas, Mexico. We show that ZIKV R0 in South Texas communities could be greater than one if the risk of human exposure to Ae. aegypti bites in these communities is at least 60% that of Northern Mexico communities. The high utilization of non-human vertebrates and low risk of human exposure in South Texas diminishes the outbreak potential for human-amplified urban arboviruses transmitted by Ae. aegypti.

Broad Antiviral Activity of Ginkgolic Acid against Chikungunya, Mayaro, Una, and Zika Viruses

The alphaviruses Chikungunya (CHIKV), Mayaro (MAYV), Una (UNAV), and the flavivirus Zika (ZIKV) are emerging or re-emerging arboviruses which are responsible for frequent epidemic outbreaks. Despite the large impact of these arboviruses on health systems, there are no approved vaccines or treatments to fight these infections. As a consequence, there is an urgent need to discover new antiviral drugs. Natural products are a rich source of compounds with distinct biological activities, including antiviral properties. Thus, we aimed to explore the potential antiviral activity of Ginkgolic acid against the arboviruses CHIKV, MAYV, UNAV, and ZIKV. Viral progeny production in supernatants from cells treated or not treated with Ginkgolic acid was quantified by plaque-forming assay. Ginkgolic acid's direct virucidal activity against these arboviruses was also determined. Additionally, viral protein expression was assessed using Western blot and immunofluorescence. Our results reveal that Ginkgolic acid promotes a dose-dependent decrease in viral titers in all tested viruses. Moreover, the compound demonstrated strong virucidal activity. Finally, we found that viral protein expression was affected by treatment with this drug. Collectively, these findings suggest that Ginkgolic acid could have broader antiviral activity.

From Anonymous to Public Enemy: How Does a Mosquito Become a Feared Arbovirus Vector?

The past few decades have seen the emergence of several worldwide arbovirus epidemics (chikungunya, Zika), the expansion or recrudescence of historical arboviruses (dengue, yellow fever), and the modification of the distribution area of major vector mosquitoes such as Aedes aegypti and Ae. albopictus, raising questions about the risk of appearance of new vectors and new epidemics. In this opinion piece, we review the factors that led to the emergence of yellow fever in the Americas, define the conditions for a mosquito to become a vector, analyse the recent example of the new status of Aedes albopictus from neglected mosquito to major vector, and propose some scenarios for the future.

Genomic Epidemiology as a Public Health Tool to Combat Mosquito-Borne Virus Outbreaks

Next-generation sequencing technologies, exponential increases in the availability of virus genomic data, and ongoing advances in phylogenomic methods have made genomic epidemiology an increasingly powerful tool for public health response to a range of mosquito-borne virus outbreaks. In this review, we offer a brief primer on the scope and methods of phylogenomic analyses that can answer key epidemiological questions during mosquito-borne virus public health emergencies. We then focus on case examples of outbreaks, including those caused by dengue, Zika, yellow fever, West Nile, and chikungunya viruses, to demonstrate the utility of genomic epidemiology to support the prevention and control of mosquito-borne virus threats. We extend these case studies with operational perspectives on how to best incorporate genomic epidemiology into structured surveillance and response programs for mosquito-borne virus control. Many tools for genomic epidemiology already exist, but so do technical and nontechnical challenges to advancing their use. Frameworks to support the rapid sharing of multidimensional data and increased cross-sector partnerships, networks, and collaborations can support advancement on all scales, from research and development to implementation by public health agencies.

Role of autophagy during the replication and pathogenesis of common mosquito-borne flavi- and alphaviruses

Arboviruses that are transmitted to humans by mosquitoes represent one of the most important causes of febrile illness worldwide. In recent decades, we have witnessed a dramatic re-emergence of several mosquito-borne arboviruses, including dengue virus (DENV), West Nile virus (WNV), chikungunya virus (CHIKV) and Zika virus (ZIKV). DENV is currently the most common mosquito-borne arbovirus, with an estimated 390 million infections worldwide annually. Despite a global effort, no specific therapeutic strategies are available to combat the diseases caused by these viruses. Multiple cellular pathways modulate the outcome of infection by either promoting or hampering viral replication and/or pathogenesis, and autophagy appears to be one of them. Autophagy is a degradative pathway generally induced to counteract viral infection. Viruses, however, have evolved strategies to subvert this pathway and to hijack autophagy components for their own benefit. In this review, we will focus on the role of autophagy in mosquito-borne arboviruses with emphasis on DENV, CHIKV, WNV and ZIKV, due to their epidemiological importance and high disease burden.

A need to raise the bar - A systematic review of temporal trends in diagnostics for Japanese encephalitis virus infection, and perspectives for future research

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Japanese encephalitis virus (JEV) remains a leading cause of neurological infection in Asia.

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A systematic review identified 20,212 published human cases of laboratory-confirmed JEV infections from 205 studies.

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15,167 (75%) of cases were confirmed with the lowest confidence diagnostic test, i.e., level 3 or 4, or level 4.

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Only 109 (53%) of the studies reported contemporaneous testing for dengue-specific antibodies.

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A fundamental pre-requisite for the control of JE is lacking — that of a simple and specific diagnostic procedure that can be adapted for point-of-care tests and readily used throughout JE endemic regions of the world.

Objective

Japanese encephalitis virus infection (JE) remains a leading cause of neurological disease in Asia, mainly involving individuals living in remote areas with limited access to treatment centers and diagnostic facilities. Laboratory confirmation is fundamental for the justification and implementation of vaccination programs. We reviewed the literature on historical developments and current diagnostic capability worldwide, to identify knowledge gaps and instill urgency to address them.

Methods

Searches were performed in Web of Science and PubMed using the term 'Japanese encephalitis' up to 13th October 2019. Studies reporting laboratory-confirmed symptomatic JE cases in humans were included, and data on details of diagnostic tests were extracted. A JE case was classified according to confirmatory levels (Fischer et al., 2008; Campbell et al., 2011; Pearce et al., 2018; Heffelfinger et al., 2017), where level 1 represented the highest level of confidence.

Findings

20,212 published JE cases were identified from 205 studies. 15,167 (75%) of these positive cases were confirmed with the lowest-confidence diagnostic tests (level 3 or 4, or level 4). Only 109 (53%) of the studies reported contemporaneous testing for dengue-specific antibodies.

Conclusion

A fundamental pre-requisite for the control of JEV is lacking — that of a simple and specific diagnostic procedure that can be adapted for point-of-care tests and readily used throughout JE-endemic regions of the world.

Opossum Cathelicidins Exhibit Antimicrobial Activity Against a Broad Spectrum of Pathogens Including West Nile Virus

This study aimed to characterize cathelicidins from the gray short-tailed opossum in silico and experimentally validate their antimicrobial effects against various pathogenic bacteria and West Nile virus (WNV). Genome-wide in silico analysis against the current genome assembly of the gray short-tailed opossum yielded 56 classical antimicrobial peptides (AMPs) from eight different families, among which 19 cathelicidins, namely ModoCath1 – 19, were analyzed in silico to predict their antimicrobial domains and three of which, ModoCath1, -5, and -6, were further experimentally evaluated for their antimicrobial activity, and were found to exhibit a wide spectrum of antimicroial effects against a panel of gram-positive and gram-negative bacterial strains. In addition, these peptides displayed low-to-moderate cytotoxicity in mammalian cells as well as stability in serum and various salt and pH conditions. Circular dichroism analysis of the spectra resulting from interactions between ModoCaths and lipopolysaccharides (LPS) showed formation of a helical structure, while a dual-dye membrane disruption assay and scanning electron microscopy analysis revealed that ModoCaths exerted bactericidal effects by causing membrane damage. Furthermore, ModoCath5 displayed potent antiviral activity against WNV by inhibiting viral replication, suggesting that opossum cathelicidins may serve as potentially novel antimicrobial endogenous substances of mammalian origin, considering their large number. Moreover, analysis of publicly available RNA-seq data revealed the expression of eight ModoCaths from five different tissues, suggesting that gray short-tailed opossums may be an interesting source of cathelicidins with diverse characteristics.

Tryptophan Trimers and Tetramers Inhibit Dengue and Zika Virus Replication by Interfering with Viral Attachment Processes

Here, we report a class of tryptophan trimers and tetramers that inhibit (at low micromolar range) dengue and Zika virus infection in vitro These compounds (AL family) have three or four peripheral tryptophan moieties directly linked to a central scaffold through their amino groups; thus, their carboxylic acid groups are free and exposed to the periphery. Structure-activity relationship (SAR) studies demonstrated that the presence of extra phenyl rings with substituents other than COOH at the N1 or C2 position of the indole side chain is a requisite for the antiviral activity against both viruses. The molecules showed potent antiviral activity, with low cytotoxicity, when evaluated on different cell lines. Moreover, they were active against laboratory and clinical strains of all four serotypes of dengue virus as well as a selected group of Zika virus strains. Additional mechanistic studies performed with the two most potent compounds (AL439 and AL440) demonstrated an interaction with the viral envelope glycoprotein (domain III) of dengue 2 virus, preventing virus attachment to the host cell membrane. Since no antiviral agent is approved at the moment against these two flaviviruses, further pharmacokinetic studies with these molecules are needed for their development as future therapeutic/prophylactic drugs.

Abundance and Updated Distribution of Aedes aegypti (Diptera: Culicidae) in Cabo Verde Archipelago: A Neglected Threat to Public Health

BACKGROUND

Mosquito-borne viruses, such as Zika, dengue, yellow fever, and chikungunya, are important causes of human diseases nearly worldwide. The greatest health risk for arboviral disease outbreaks is the presence of the most competent and highly invasive domestic mosquito, Aedes aegypti. In Cabo Verde, two recent arbovirus outbreaks were reported, a dengue outbreak in 2009, followed by a Zika outbreak in 2015. This study is the first entomological survey for Ae. aegypti that includes all islands of Cabo Verde archipelago, in which we aim to evaluate the actual risk of vector-borne arboviruses as a continuous update of the geographical distribution of this species.

METHODS

In order to assess its current distribution and abundance, we undertook a mosquito larval survey in the nine inhabited islands of Cabo Verde from November 2018 to May 2019. Entomological larval survey indices were calculated, and the abundance analyzed. We collected and identified 4045 Ae. aegypti mosquitoes from 264 positive breeding sites in 22 municipalities and confirmed the presence of Ae. aegypti in every inhabited island. Results: Water drums were found to be the most prevalent containers (n = 3843; 62.9%), but puddles (n = 27; 0.4%) were the most productive habitats found. The overall average of the House, Container, and Breteau larval indices were 8.4%, 4.4%, and 10.9, respectively. However, 15 out of the 22 municipalities showed that the Breteau Index was above the epidemic risk threshold.

CONCLUSION

These results suggest that if no vector control measures are considered to be in place, the risk of new arboviral outbreaks in Cabo Verde is high. The vector control strategy adopted must include measures of public health directed to domestic water storage and management.

Oropouche infection a neglected arbovirus in patients with acute febrile illness from the Peruvian coast

Objective

To evaluate the frequency of infection caused by the Oropouche virus (OROV) in 496 patients with acute febrile disease (AFI), whose samples were obtained for the analysis of endemic arboviruses in a previous investigation carried out in 2016.

Results

OROV was detected in 26.4% (131/496) of serum samples from patients with AFI. Co-infections with Dengue virus (7.3%), Zika virus (1.8%) and Chikungunya (0.2%) were observed. The most common clinical symptoms reported among the patients with OROV infections were headache 85.5% (112/131), myalgia 80.9% (106/131), arthralgia 72.5% (95/131) and loss of appetite 67.9% (89/131). Headache and myalgia were predominant in all age groups. Both OROV infections and co-infections were more frequent in May, June and July corresponding to the dry season of the region.

Perspectives Regarding the Risk of Introduction of the Japanese Encephalitis Virus (JEV) in the United States

Japanese encephalitis (JE) is a zoonotic, emerging disease transmitted by mosquito vectors infected with the Japanese encephalitis virus (JEV). Its potential for emergence into susceptible regions is high, including in the United States (US), and is a reason of economic concern among the agricultural community, and to public health due to high morbidity and mortality rates in humans. While exploring the complexities of interactions involved with viral transmission, we proposed a new outlook on the role of vectors, hosts and the environment under changing conditions. For instance, the role of feral pigs may have been underappreciated in our previous work, given research keeps pointing to the importance of susceptible populations of wild swine in naïve regions as key elements for the introduction of emergent vector-borne diseases. High risk of JEV introduction has been associated with the transportation of infected mosquitoes via aircraft. Nonetheless, no JEV outbreaks have been reported in the US to date and results from a qualitative risk assessment considered the risk of establishment to be negligible under the current conditions (environmental, vector, pathogen, and host). In this work, we discuss virus-vector-host interactions and ecological factors important for virus transmission and spread, review research on the risk of JEV introduction to the US considering the implications of risk dismissal as it relates to past experiences with similar arboviruses, and reflect on future directions, challenges, and implications of a JEV incursion.

Ecological aspects of potential arbovirus vectors (Diptera: Culicidae) in an urban landscape of Southern Amazon, Brazil

Amazon has been under intense human pressure, especially in the so-called "Arc of Deforestation" in the Eastern and Southern regions. Changes in biodiversity due to landscape disturbance in municipalities at the Arc of Deforestation are likely to impact mosquito species leading to the potential for emergence of arboviruses. Our aim was to describe the composition and structure of culicids in Sinop, a municipality located in the Southern Amazon at the State of Mato Grosso, as well as their presence in urban habitats, analyzing climate variables and potential risk of arbovirus transmission. Mosquitoes were collected in four habitats located in urban environments for 12 months. We recovered 5,210 adult mosquitoes from mosquito traps. Among the 33 species identified, 19 are associated with arbovirus transmission. Higher abundance, richness, diversity, and equitability of mosquito species were observed in urban forest parks and in new neighborhoods located in the outskirts of the city, nearby forest fragments and agricultural areas. As the environment consolidates as urban, both abundance and richness decrease. Highly urbanized neighborhoods had higher dominance of Culex quinquefasciatus, a mosquito associated with different arboviruses, including West Nile and Saint Louis encephalitis virus. The medically important species Cx. declarator, Cx. (Melanoconion) ssp., Aedeomyia squamipennis and Aedes scapularis were found in the four habitats. It is possible that these mosquitoes are adapting to different habitats and as a consequence, they are reaching urbanized areas. Mosquito abundance was higher in the days of high temperature and low precipitation in urban forest parks and in highly urbanized neighborhoods. These results suggest that Sinop region is a key area for surveillance of arbovirus vectors.

Tudor-SN Promotes Early Replication of Dengue Virus in the Aedes aegypti Midgut

Diseases caused by mosquito-borne viruses have been on the rise for the last decades, and novel methods aiming to use laboratory-engineered mosquitoes that are incapable of carrying viruses have been developed to reduce pathogen transmission. This has stimulated efforts to identify optimal target genes that are naturally involved in mosquito antiviral defenses or required for viral replication. Here, we investigated the role of a member of the Tudor protein family, Tudor-SN, upon dengue virus infection in the mosquito Aedes aegypti. Tudor-SN knockdown reduced dengue virus replication in the midgut of Ae. aegypti females. In immunofluorescence assays, Tudor-SN localized to the nucleolus in both Ae. aegypti and Aedes albopictus cells. A reporter assay and small RNA profiling demonstrated that Tudor-SN was not required for RNA interference function in vivo. Collectively, these results defined a novel proviral role for Tudor-SN upon early dengue virus infection of the Ae. aegypti midgut.

Entomological Assessment of the Status and Risk of Mosquito-borne Arboviral Transmission in Ghana

Entomological surveillance is one of the tools used in monitoring and controlling vector-borne diseases. However, the use of entomological surveillance for arboviral infection vector control is often dependent on finding infected individuals. Although this method may suffice in highly endemic areas, it is not as effective in controlling the spread of diseases in low endemic and non-endemic areas. In this study, we examined the efficiency of using entomological markers to assess the status and risk of arbovirus infection in Ghana, which is considered a non-endemic country, by combining mosquito surveillance with virus isolation and detection. This study reports the presence of cryptic species of mosquitoes in Ghana, demonstrating the need to combine morphological identification and molecular techniques in mosquito surveillance. Furthermore, although no medically important viruses were detected, the importance of insect-specific viruses in understanding virus evolution and arbovirus transmission is discussed. This study reports the first mutualistic relationship between dengue virus and the double-stranded RNA Aedes aegypti totivirus. Finally, this study discusses the complexity of the virome of Aedes and Culex mosquitoes and its implication for arbovirus transmission.

Complete Genome Sequences of Dengue Virus Type 2 Epidemic Strains from Reunion Island and the Seychelles

Dengue virus has recently reemerged in the southern Indian Ocean islands, causing outbreaks in Reunion Island and the Seychelles. In the present study, we determined the complete genome sequences of closely related clinical isolates of dengue virus type 2 circulating in the Seychelles in 2016 and Reunion Island in 2018.

Dengue virus has recently reemerged in the southern Indian Ocean islands, causing outbreaks in Reunion Island and the Seychelles. In the present study, we determined the complete genome sequences of closely related clinical isolates of dengue virus type 2 circulating in the Seychelles in 2016 and Reunion Island in 2018.

Insecticide resistance genes affect Culex quinquefasciatus vector competence for West Nile virus

Insecticide resistance has been reported to impact the interactions between mosquitoes and the pathogens they transmit. However, the effect on vector competence for arboviruses still remained to be investigated. We examined the influence of two insecticide resistance mechanisms on vector competence of the mosquito Culex quinquefasciatus for two arboviruses, Rift Valley Fever virus (RVFV) and West Nile virus (WNV). Three Cx. quinquefasciatus lines sharing a common genetic background were used: two insecticide-resistant lines, one homozygous for amplification of the Ester² locus (SA2), the other homozygous for the acetylcholinesterase ace-1 G119S mutation (SR) and the insecticide-susceptible reference line Slab. Statistical analyses revealed no significant effect of insecticide-resistant mechanisms on vector competence for RVFV. However, both insecticide resistance mechanisms significantly influenced the outcome of WNV infections by increasing the dissemination of WNV in the mosquito body, therefore leading to an increase in transmission efficiency by resistant mosquitoes. These results showed that insecticide resistance mechanisms enhanced vector competence for WNV and may have a significant impact on transmission dynamics of arboviruses. Our findings highlight the importance of understanding the impacts of insecticide resistance on the vectorial capacity parameters to assess the overall consequence on transmission.