Eastern Equine Encephalitis Virus: A Scoping Review of the Global Evidence

Powassan and other emerging neuroinvasive arboviruses in North America

PURPOSE OF REVIEW

Arthropod-borne viruses (arboviruses) represent a group of pathogens with increasing global relevance, some of which cause neuroinvasive disease. Transmitted by arthropod vectors and maintained by a variety of primary and amplifying hosts, epidemics are dependent on numerous environmental and anthropogenic factors. This review serves to highlight several important neuroinvasive arboviruses relevant to North America and discuss the neurologic presentations, diagnosis, outcomes, and future trends.

RECENT FINDINGS

Recent shifts in the epidemiology and ecology of arboviruses in North America include the divergence of arboviruses such as dengue and chikungunya from dependence on enzootic cycles, the geographical expansion of Oropouche virus, and the increasing incidence of some established North American arboviruses such as Powassan virus. Accurate identification of the factors contributing to arboviral outbreaks is critical to improve preventive public health measures. Similarly, further elucidating the relevant pathogen and host factors that determine neuroinvasiveness, neurotropism, and neurovirulence will be key to the development of successful vaccines and targeted therapeutics.

SUMMARY

Arboviruses are an important pathogen relevant to human disease. Familiarity with the presentations, diagnostic workup, treatment and preventive strategies, and expected course is critical for clinicians caring for these patients.

Serologic Surveillance for Orthoflaviviruses and Chikungunya Virus in Bats and Opossums in Chiapas, Mexico

We performed serologic surveillance for selected arthropod-borne viruses (arboviruses) in bats and opossums in the Lacandona Rainforest, Chiapas, Mexico, in 2023-2024. Sera were collected from 94 bats of at least 15 species and 43 opossums of three species. The sera were assayed by the plaque reduction neutralization test (PRNT) for antibodies to eight orthoflaviviruses (dengue viruses 1-4, St. Louis encephalitis virus, T'Ho virus, West Nile virus, and Zika virus) and one alphavirus (chikungunya virus; CHIKV). Twelve (12.8%) bats and 15 (34.9%) opossums contained orthoflavivirus-specific antibodies. One bat (a Jamaican fruit bat) was seropositive for Zika virus, and 11 bats contained antibodies to an undetermined orthoflavivirus, as did the 15 opossums. All bats and most opossums seropositive for an undetermined orthoflavivirus had low PRNT titers, possibly because they had been infected with another (perhaps unrecognized) orthoflavivirus not included in the PRNTs. Antibodies that neutralized CHIKV were detected in three (7.0%) opossums and none of the bats. The three opossums had low CHIKV PRNT titers, and therefore, another alphavirus may have been responsible for the infections. In summary, we report serologic evidence of arbovirus infections in bats and opossums in Chiapas, Mexico.

Eastern equine encephalitis virus: Pathogenesis, immune response, and clinical manifestations

Eastern equine encephalitis virus (EEEV) is a lethal Alphavirus transmitted by Culiseta melanura mosquitoes that primarily cycles between birds. Although rare, infections in humans and horses are associated with high mortality rates and severe neurological effects. Climate change appears to be increasing the spread of this virus. This study aims to provide a comprehensive analysis of EEEV, including its transmission dynamics, pathogenesis, induced host immune response, and long-term impacts on survivors. It also highlights the virus's unique immune evasion strategies that complicate disease management and contribute to severe clinical outcomes, such as encephalitis with fever, convulsions, and coma. Survivors often face chronic cognitive, motor, and psychosocial impairments. Despite these significant public health risks, gaps remain in understanding the molecular mechanisms underlying immune evasion and the long-term neurological sequelae in survivors. By collating current knowledge, this review underscores the urgent need for the development of targeted vaccines and therapeutic interventions to mitigate the growing threat of EEEV, particularly in the context of climate change-driven geographical expansion.

Low capacity for molecular detection of Alphaviruses other than Chikungunya virus in 23 European laboratories, March 2022

Alphaviruses comprise over 30 identified species spread worldwide and carry a large global health burden. With vector expansion occurring in and around Europe, it is anticipated this burden will increase. Therefore, regular assessment of the diagnostic capabilities in Europe is important, e.g., by conducting external quality assessments (EQAs). Here we evaluated molecular detection of alphaviruses in expert European laboratories by conducting an EQA in March 2022. Molecular panels included 15 samples: nine alphaviruses, Barmah Forest virus (BFV), chikungunya virus (CHIKV), Eastern equine encephalitis virus (EEEV), Mayaro virus (MAYV), o'nyong-nyong virus (ONNV), Ross River virus (RRV), Sindbis virus (SINV), Venezuelan equine encephalitis virus (VEEV), and Western equine encephalitis virus (WEEV) and four negative control samples. Alphavirus detection was assessed among 23 laboratories in 16 European countries. Adequate capabilities were lacking for several viruses, and approximately half of the laboratories (11/23) relied on pan-alphavirus assays with varying sensitivity and specificity. Only 46% of laboratories characterized all EQA samples correctly. Correct result rates were > 90% for CHIKV, RRV and SINV, but laboratories lacked specificity for ONNV and MAYV and sensitivity for VEEV, BFV, and EEEV. Only two alphaviruses causing human disease circulate or have circulated in Europe, CHIKV and SINV. Molecular detection was satisfactory with both CHIKV and SINV, but < 50% correct for the entire alphaviruses panel. With continued imported cases, and a growing global concern about climate change and vector expansion, focus on progress toward rapid, accurate alphavirus diagnostics in Europe is recommended, as well as regular EQAs to monitor quality.

Public health significance of the white-tailed deer (Odocoileus virginianus) and its role in the eco-epidemiology of tick- and mosquito-borne diseases in North America

White-tailed deer (Odocoileus virginianus) are a ubiquitous species in North America. Their high reproductive potential leads to rapid population growth, and they exhibit a wide range of biological adaptations that influence their interactions with vectors and pathogens. This review aims to characterize the intricate interplay between white-tailed deer and the transmission cycles of various tick- and mosquito-borne pathogens across their range in the eastern United States and southeastern Canada. The first part offers insights into the biological characteristics of white-tailed deer, their population dynamics, and the consequential impacts on both the environment and public health. This contextual backdrop sets the stage for the two subsequent sections, which delve into specific examples of pathogen transmission involving white-tailed deer categorized by tick and mosquito vectors into tick-borne and mosquito-borne diseases. This classification is essential, as ticks and mosquitoes serve as pivotal elements in the eco-epidemiology of vector-borne diseases, intricately linking hosts, the environment, and pathogens. Through elucidating these associations, this paper highlights the crucial role of white-tailed deer in the transmission dynamics of tick- and mosquito-borne diseases. Understanding the interactions between white-tailed deer, vectors, and pathogens is essential for effective disease management and public health interventions.

Innovative strategies and challenges mosquito-borne disease control amidst climate change

The revival of the transmission dynamics of mosquito-borne diseases grants striking challenges to public health intensified by climate change worldwide. This inclusive review article examines multidimensional strategies and challenges linked to climate change and the epidemiology of mosquito-borne diseases such as malaria, dengue, Zika, chikungunya, and yellow fever. It delves into how the biology, pathogenic dynamics, and vector distribution of mosquitoes are influenced by continuously rising temperatures, modified rainfall patterns, and extreme climatic conditions. We also highlighted the high likelihood of malaria in Africa, dengue in Southeast Asia, and blowout of Aedes in North America and Europe. Modern predictive tools and developments in surveillance, including molecular gears, Geographic Information Systems (GIS), and remote sensing have boosted our capacity to predict epidemics. Integrated data management techniques and models based on climatic conditions provide a valuable understanding of public health planning. Based on recent data and expert ideas, the objective of this review is to provide a thoughtful understanding of existing landscape and upcoming directions in the control of mosquito-borne diseases regarding changing climate. This review determines emerging challenges and innovative vector control strategies in the changing climatic conditions to ensure public health.

Structural basis for VLDLR recognition by eastern equine encephalitis virus

Eastern equine encephalitis virus (EEEV) is the most virulent alphavirus that infects humans, and many survivors develop neurological sequelae, including paralysis and intellectual disability. Alphavirus spike proteins comprise trimers of heterodimers of glycoproteins E2 and E1 that mediate binding to cellular receptors and fusion of virus and host cell membranes during entry. We recently identified very-low density lipoprotein receptor (VLDLR) and apolipoprotein E receptor 2 (ApoER2) as cellular receptors for EEEV and a distantly related alphavirus, Semliki Forest virus (SFV). Here, we use single-particle cryo-electron microscopy (cryo-EM) to determine structures of the EEEV and SFV spike glycoproteins bound to the VLDLR ligand-binding domain and found that EEEV and SFV interact with the same cellular receptor through divergent binding modes. Our studies suggest that the ability of LDLR-related proteins to interact with viral spike proteins through very small footprints with flexible binding modes results in a low evolutionary barrier to the acquisition of LDLR-related proteins as cellular receptors for diverse sets of viruses.

Inactivation of highly transmissible livestock and avian viruses including influenza A and Newcastle disease virus for molecular diagnostics

There is a critical need for an inactivation method that completely inactivates pathogens at the time of sample collection while maintaining the nucleic acid quality required for diagnostic PCR testing. This inactivation method is required to alleviate concerns about transmission potential, minimize shipping complications and cost, and enable testing in lower containment laboratories, thereby enhancing disease diagnostics through improved turn-around time. This study evaluated a panel of 10 surrogate viruses that represent highly pathogenic animal diseases. These results showed that a commercial PrimeStore® molecular transport media (PSMTM) completely inactivated all viruses tested by >99.99%, as determined by infectivity and serial passage assays. However, the detection of viral nucleic acid by qRT-PCR was comparable in PSMTM and control-treated conditions. These results were consistent when viruses were evaluated in the presence of biological material such as sera and cloacal swabs to mimic diagnostic sample conditions for non-avian and avian viruses, respectively. The results of this study may be utilized by diagnostic testing laboratories for highly pathogenic agents affecting animal and human populations. These results may be used to revise guidance for select agent diagnostic testing and the shipment of infectious substances.

Eastern Equine Encephalitis Virus: A Case Report and Brief Literature Review of Current Therapeutic and Preventative Strategies

Background: Eastern equine encephalitis virus (EEEV) is a rare mosquito-borne illness exhibiting rapid neurological deterioration and permanent damage. Despite its >30% mortality and >60% long-term neurological damage, EEEV has no approved antiviral medication or vaccination. This report uniquely aims to describe a rare case of EEEV and provide a current literature review of therapeutic and preventative options from the clinical perspective to guide clinicians and public health workers, along with informing them about its impact and current knowledge gaps. Methods: A retrospective chart review of the electronic medical record was performed for a patient's 10-day hospital admission in July 2021. In addition, PubMed was searched using relevant keywords for a literature review of EEEV. Results: A 61-year-old woman presented with dysarthria and right-sided facial droop. Acute ischemic stroke was ruled out, and empiric intravenous (IV) antibiotics were initiated for possible infectious etiology. The patient developed worsening mental status and fever and was intubated, with antibiotics broadened with concern for meningitis along with tick-borne illness. The patient remained encephalopathic and febrile, and lumbar serologies were consistent with viral meningoencephalitis or acute disseminated encephalomyelitis. Several days after collection, quantitative antibody testing returned positive for EEEV. The patient was pronounced dead on hospital day 10. On review of the literature regarding EEEV, supportive care and prevention remain the cornerstone of management. Although early IV immunoglobulin and high-dose steroids have shown potential as treatments to reduce morbidity and mortality, no vaccines have been approved to date. Conclusion: Prospective trials and further investigations into treatment and preventative options may be useful in reducing the morbidity and mortality associated with EEEV.

Designing a Multiepitope Vaccine against Eastern Equine Encephalitis Virus: Immunoinformatics and Computational Approaches

Eastern equine encephalitis virus (EEEV) is a significant threat to human and animal populations, causing severe encephalitis, often leading to long-term neurological complications and even mortality. Despite this, no approved antiviral treatments or EEEV human vaccines currently exist. In response, we utilized immunoinformatics and computational approaches to design a multiepitope vaccine candidate for EEEV. By screening the structural polyprotein of EEEV, we predicted both T-cell and linear B-cell epitopes. These epitopes underwent comprehensive evaluations for their antigenicity, toxicity, and allergenicity. From these evaluations, we selected ten epitopes highly suitable for vaccine design, which were connected with adjuvants using a stable linker. The resulting vaccine construct demonstrated exceptional antigenic, nontoxic, nonallergenic, and physicochemical properties. Subsequently, we employed molecular docking and molecular dynamics simulations to reveal a stable interaction pattern between the vaccine candidate and Toll-like receptor 5. Besides, computational immune simulations predicted the vaccine's capability to induce robust immune responses. Our study addresses the urgent need for effective EEEV preventive strategies and offers valuable insights for EEEV vaccine development. As EEEV poses a severe threat with potential spread due to climate change, our research provides a crucial step in enhancing public health defenses against this menacing zoonotic disease.

Structural basis for VLDLR recognition by eastern equine encephalitis virus

Alphaviruses are arthropod-borne enveloped RNA viruses that include several important human pathogens with outbreak potential. Among them, eastern equine encephalitis virus (EEEV) is the most virulent, and many survivors develop neurological sequelae, including paralysis and intellectual disability. The spike proteins of alphaviruses comprise trimers of heterodimers of their envelope glycoproteins E2 and E1 that mediate binding to cellular receptors and fusion of virus and host cell membranes during entry. We recently identified very-low density lipoprotein receptor (VLDLR) and apolipoprotein E receptor 2 (ApoER2), two closely related proteins that are expressed in the brain, as cellular receptors for EEEV and a distantly related alphavirus, Semliki forest virus (SFV) 1 . The EEEV and SFV spike glycoproteins have low sequence homology, and how they have evolved to bind the same cellular receptors is unknown. Here, we used single-particle cryo-electron microscopy (cryo-EM) to determine structures of the EEEV and SFV spike glycoproteins bound to the VLDLR ligand-binding domain. The structures reveal that EEEV and SFV use distinct surfaces to bind VLDLR; EEEV uses a cluster of basic residues on the E2 subunit of its spike glycoprotein, while SFV uses two basic residues at a remote site on its E1 glycoprotein. Our studies reveal that different alphaviruses interact with the same cellular receptor through divergent binding modes. They further suggest that the ability of LDLR-related proteins to interact with viral spike proteins through very small footprints with flexible binding modes results in a low evolutionary barrier to the acquisition of LDLR-related proteins as cellular receptors for diverse sets of viruses.

Genus Culex Linnaeus, 1758 (Diptera: Culicidae) as an Important Potential Arbovirus Vector in Brazil: An Integrative Review

The genus Culex has 817 species subdivided into 28 subgenera. It has a cosmopolitan distribution, being most abundant in countries with a tropical climate. Understanding the ecology and diversity of viruses circulating in the species of this genus is important for understanding their role as arbovirus vectors in Brazil. To conduct an integrative review to identify the importance of the Culex genus as arbovirus vectors in Brazil. A search was carried out for scientific papers in the PubMed, BVSalud, Patuá-IEC and International Catalogue of Arboviruses: including certain other viruses of vertebrates databases. 36 publications describing arbovirus detections in Culex mosquitoes collected in the field in Brazil were evaluated. A total of 42 arbovirus species were detected, as well as studies analyzing the vector competence of C. quinquefasciatus for the transmission of four different arboviruses. The study of the Culex genus and its role as a vector of arboviruses in Brazil is essential for understanding transmission cycles, with the main aim of reducing cases of human infection. Thus, entomovirological surveillance guides the implementation of actions to detect circulating arboviruses among vectors to anticipate measures aimed at preventing or reducing the risk of arbovirus outbreaks in the country.

Emerging and Novel Viruses in Passerine Birds

There is growing interest in emerging viruses that can cause serious or lethal disease in humans and animals. The proliferation of cloacal virome studies, mainly focused on poultry and other domestic birds, reveals a wide variety of viruses, although their pathogenic significance is currently uncertain. Analysis of viruses detected in wild birds is complex and often biased towards waterfowl because of the obvious interest in avian influenza or other zoonotic viruses. Less is known about the viruses present in the order Passeriformes, which comprises approximately 60% of extant bird species. This review aims to compile the most significant contributions on the DNA/RNA viruses affecting passerines, from traditional and metagenomic studies. It highlights that most passerine species have never been sampled. Especially the RNA viruses from Flaviviridae, Orthomyxoviridae and Togaviridae are considered emerging because of increased incidence or avian mortality/morbidity, spread to new geographical areas or hosts and their zoonotic risk. Arguably poxvirus, and perhaps other virus groups, could also be considered "emerging viruses". However, many of these viruses have only recently been described in passerines using metagenomics and their role in the ecosystem is unknown. Finally, it is noteworthy that only one third of the viruses affecting passerines have been officially recognized.

Dynamics of eastern equine encephalitis virus during the 2019 outbreak in the Northeast United States

Eastern equine encephalitis virus (EEEV) causes a rare but severe disease in horses and humans and is maintained in an enzootic transmission cycle between songbirds and Culiseta melanura mosquitoes. In 2019, the largest EEEV outbreak in the United States for more than 50 years occurred, centered in the Northeast. To explore the dynamics of the outbreak, we sequenced 80 isolates of EEEV and combined them with existing genomic data. We found that, similar to previous years, cases were driven by multiple independent but short-lived virus introductions into the Northeast from Florida. Once in the Northeast, we found that Massachusetts was important for regional spread. We found no evidence of any changes in viral, human, or bird factors which would explain the increase in cases in 2019, although the ecology of EEEV is complex and further data is required to explore these in more detail. By using detailed mosquito surveillance data collected by Massachusetts and Connecticut, however, we found that the abundance of Cs. melanura was exceptionally high in 2019, as was the EEEV infection rate. We employed these mosquito data to build a negative binomial regression model and applied it to estimate early season risks of human or horse cases. We found that the month of first detection of EEEV in mosquito surveillance data and vector index (abundance multiplied by infection rate) were predictive of cases later in the season. We therefore highlight the importance of mosquito surveillance programs as an integral part of public health and disease control.

Interactions of Equine Viruses with the Host Kinase Machinery and Implications for One Health and Human Disease

Zoonotic pathogens that are vector-transmitted have and continue to contribute to several emerging infections globally. In recent years, spillover events of such zoonotic pathogens have increased in frequency as a result of direct contact with livestock, wildlife, and urbanization, forcing animals from their natural habitats. Equines serve as reservoir hosts for vector-transmitted zoonotic viruses that are also capable of infecting humans and causing disease. From a One Health perspective, equine viruses, therefore, pose major concerns for periodic outbreaks globally. Several equine viruses have spread out of their indigenous regions, such as West Nile virus (WNV) and equine encephalitis viruses (EEVs), making them of paramount concern to public health. Viruses have evolved many mechanisms to support the establishment of productive infection and to avoid host defense mechanisms, including promoting or decreasing inflammatory responses and regulating host machinery for protein synthesis. Viral interactions with the host enzymatic machinery, specifically kinases, can support the viral infectious process and downplay innate immune mechanisms, cumulatively leading to a more severe course of the disease. In this review, we will focus on how select equine viruses interact with host kinases to support viral multiplication.

Latest Advances in Arbovirus Diagnostics

Arboviruses are a diverse family of vector-borne pathogens that include members of the Flaviviridae, Togaviridae, Phenuviridae, Peribunyaviridae, Reoviridae, Asfarviridae, Rhabdoviridae, Orthomyxoviridae and Poxviridae families. It is thought that new world arboviruses such as yellow fever virus emerged in the 16th century due to the slave trade from Africa to America. Severe disease-causing viruses in humans include Japanese encephalitis virus (JEV), yellow fever virus (YFV), dengue virus (DENV), West Nile virus (WNV), Zika virus (ZIKV), Crimean-Congo hemorrhagic fever virus (CCHFV), severe fever with thrombocytopenia syndrome virus (SFTSV) and Rift Valley fever virus (RVFV). Numerous methods have been developed to detect the presence of these pathogens in clinical samples, including enzyme-linked immunosorbent assays (ELISAs), lateral flow assays (LFAs) and reverse transcriptase-polymerase chain reaction (RT-PCR). Most of these assays are performed in centralized laboratories due to the need for specialized equipment, such as PCR thermal cyclers and dedicated infrastructure. More recently, molecular methods have been developed which can be performed at a constant temperature, termed isothermal amplification, negating the need for expensive thermal cycling equipment. In most cases, isothermal amplification can now be carried out in as little as 5-20 min. These methods can potentially be used as inexpensive point of care (POC) tests and in-field deployable applications, thus decentralizing the molecular diagnosis of arboviral disease. This review focuses on the latest developments in isothermal amplification technology and detection techniques that have been applied to arboviral diagnostics and highlights future applications of these new technologies.

Development of a recombinant reporter Getah virus for antiviral drug screening assays

Getah virus (GETV), is an often neglected and re-emerging mosquito-borne RNA virus. GETV can cause illness accompanied with high fever, rash, incapacitating arthralgia and chronic arthritis or encephalitic disease in affected animals. Currently, there is no specific treatment or vaccine against GETV infection. In this study, we developed three recombinant viruses by inserting different reporter protein genes between the Cap and pE2 genes. The reporter viruses exhibited high replication capacity similar to the parental virus. The rGECiLOV and rGECGFP viruses were genetically stable within at least ten rounds of passages in BHK-21 cells. We confirmed that the reporter virus, rGECGFP, facilitated the antiviral assays against GETV by testing it with the known inhibitor, ribavirin. It was also found that the compound, doxycycline, showed an inhibitory effect on GETV replication. In addition, rGECGFP was found to be an authentic mimic of the parental virus infection in 3-day-old mice, but with milder pathogenicity. The reporter viruses will contribute to the assessment of viral replication and proliferation, tracking and elucidating of alphavirus-host interactions. In addition, they will help in the screening of potential antiviral compounds.

Eastern, Western, and Venezuelan Equine Encephalitis and West Nile Viruses: Clinical and Public Health Considerations

The continued recognition and emergence of alphavirus and flavivirus diseases is a growing veterinary and public health concern. As the global environment continues to change, mosquito-borne diseases will continue to evolve and expand. Continued development of readily available vaccines for the prevention of these diseases in humans and animals is essential to controlling epizootics of these diseases. Further research into effective antiviral treatments is also sorely needed. This article describes equine encephalitis viruses with a focus on clinical and public health considerations.

Dynamics of Eastern equine encephalitis virus during the 2019 outbreak in the Northeast United States

Eastern equine encephalitis virus (EEEV) causes a rare but severe disease in horses and humans, and is maintained in an enzootic transmission cycle between songbirds and Culiseta melanura mosquitoes. In 2019, the largest EEEV outbreak in the United States for more than 50 years occurred, centered in the Northeast. To explore the dynamics of the outbreak, we sequenced 80 isolates of EEEV and combined them with existing genomic data. We found that, like previous years, cases were driven by frequent short-lived virus introductions into the Northeast from Florida. Once in the Northeast, we found that Massachusetts was important for regional spread. We found no evidence of any changes in viral, human, or bird factors which would explain the increase in cases in 2019. By using detailed mosquito surveillance data collected by Massachusetts and Connecticut, however, we found that the abundance of Cs. melanura was exceptionally high in 2019, as was the EEEV infection rate. We employed these mosquito data to build a negative binomial regression model and applied it to estimate early season risks of human or horse cases. We found that the month of first detection of EEEV in mosquito surveillance data and vector index (abundance multiplied by infection rate) were predictive of cases later in the season. We therefore highlight the importance of mosquito surveillance programs as an integral part of public health and disease control.

Inhibitors of the Ubiquitin-Mediated Signaling Pathway Exhibit Broad-Spectrum Antiviral Activities against New World Alphaviruses

New World alphaviruses including Venezuelan Equine Encephalitis Virus (VEEV) and Eastern Equine Encephalitis Virus (EEEV) are mosquito-transmitted viruses that cause disease in humans and equines. There are currently no FDA-approved therapeutics or vaccines to treat or prevent exposure-associated encephalitic disease. The ubiquitin proteasome system (UPS)-associated signaling events are known to play an important role in the establishment of a productive infection for several acutely infectious viruses. The critical engagement of the UPS-associated signaling mechanisms by many viruses as host–pathogen interaction hubs led us to hypothesize that small molecule inhibitors that interfere with these signaling pathways will exert broad-spectrum inhibitory activity against alphaviruses. We queried eight inhibitors of the UPS signaling pathway for antiviral outcomes against VEEV. Three of the tested inhibitors, namely NSC697923 (NSC), bardoxolone methyl (BARM) and omaveloxolone (OMA) demonstrated broad-spectrum antiviral activity against VEEV and EEEV. Dose dependency and time of addition studies suggest that BARM and OMA exhibit intracellular and post-entry viral inhibition. Cumulatively, our studies indicate that inhibitors of the UPS-associated signaling pathways exert broad-spectrum antiviral outcomes in the context of VEEV and EEEV infection, supporting their translational application as therapeutic candidates to treat alphavirus infections.

Application of a Human Blood Brain Barrier Organ-on-a-Chip Model to Evaluate Small Molecule Effectiveness against Venezuelan Equine Encephalitis Virus

The blood brain barrier (BBB) is a multicellular microenvironment that plays an important role in regulating bidirectional transport to and from the central nervous system (CNS). Infections by many acutely infectious viruses such as alphaviruses and flaviviruses are known to impact the integrity of the endothelial lining of the BBB. Infection by Venezuelan Equine Encephalitis Virus (VEEV) through the aerosol route causes significant damage to the integrity of the BBB, which contributes to long-term neurological sequelae. An effective therapeutic intervention strategy should ideally not only control viral load in the host, but also prevent and/or reverse deleterious events at the BBB. Two dimensional monocultures, including trans-well models that use endothelial cells, do not recapitulate the intricate multicellular environment of the BBB. Complex in vitro organ-on-a-chip models (OOC) provide a great opportunity to introduce human-like experimental models to understand the mechanistic underpinnings of the disease state and evaluate the effectiveness of therapeutic candidates in a highly relevant manner. Here we demonstrate the utility of a neurovascular unit (NVU) in analyzing the dynamics of infection and proinflammatory response following VEEV infection and therapeutic effectiveness of omaveloxolone to preserve BBB integrity and decrease viral and inflammatory load.

Spatiotemporal Environmental Drivers of Eastern Equine Encephalitis Virus in Central Florida: Towards a Predictive Model for a Lethal Disease

Eastern equine encephalitis virus (EEEV) is a mosquito-borne virus that affects humans and horses, with a high case fatality rate in both species. The virus can be transmitted by several mosquito species and maintained in multiple reservoir hosts, making EEEV dynamics difficult to anticipate. In this study, we identified spatial and temporal factors that precede EEEV detection using sentinel chicken surveillance data from Orange County, Florida, from 2003 to 2017. We first examined the land cover and mosquito species composition associated with sentinel chicken sites. We then fit distributed lag nonlinear models of EEEV detection at the county scale, using monthly temperature, precipitation, and Southern Oscillation Index values, and at the sentinel flock-scale, using remotely sensed temperature and wetness indicators. We found positive associations between the percent wooded wetlands and the count of EEEV detections. We found Culiseta melanura (Diptera: Culicidae) were more abundant at positive sites in winter and summer, but Coquillettidia perturbans (Walker) were more abundant at positive sites in spring. In the county-wide model, precipitation, temperature, and Southern Oscillation Index values at lags of two, nine, and twelve months were significant, respectively, while temperature and wetness were significant at lags of eight and six months in the flock-specific models.

Arboviral Equine Encephalitides

A number of viruses transmitted by biological vectors or through direct contact, air, or ingestion cause neurologic disease in equids. Of interest are viruses of the Togaviridae, Flaviviridae, Rhabdoviridae, Herpesviridae, Bornaviridae, and Bunyaviridae families. Many are classified as arboviruses because they use arthropod vectors, whereas others are transmitted directly via ingestion, inhalation, or integument damage. The goal of this article is to provide an overview on pathophysiologic and clinical aspects of arboviruses of equine importance, including alphaviruses (Togaviridae) and flaviviruses (Flaviviridae).

EGR1 Upregulation during Encephalitic Viral Infections Contributes to Inflammation and Cell Death

Early growth response 1 (EGR1) is an immediate early gene and transcription factor previously found to be significantly upregulated in human astrocytoma cells infected with Venezuelan equine encephalitis virus (VEEV). The loss of EGR1 resulted in decreased cell death but had no significant impact on viral replication. Here, we extend these studies to determine the impacts of EGR1 on gene expression following viral infection. Inflammatory genes CXCL3, CXCL8, CXCL10, TNF, and PTGS2 were upregulated in VEEV-infected cells, which was partially dependent on EGR1. Additionally, transcription factors, including EGR1 itself, as well as ATF3, FOS, JUN, KLF4, EGR2, and EGR4 were found to be partially transcriptionally dependent on EGR1. We also examined the role of EGR1 and the changes in gene expression in response to infection with other alphaviruses, including eastern equine encephalitis virus (EEEV), Sindbis virus (SINV), and chikungunya virus (CHIKV), as well as Zika virus (ZIKV) and Rift Valley fever virus (RVFV), members of the Flaviviridae and Phenuiviridae families, respectively. EGR1 was significantly upregulated to varying degrees in EEEV-, CHIKV-, RVFV-, SINV-, and ZIKV-infected astrocytoma cells. Genes that were identified as being partially transcriptionally dependent on EGR1 in infected cells included ATF3 (EEEV, CHIKV, ZIKV), JUN (EEEV), KLF4 (SINV, ZIKV, RVFV), CXCL3 (EEEV, CHIKV, ZIKV), CXCL8 (EEEV, CHIKV, ZIKV, RVFV), CXCL10 (EEEV, RVFV), TNF-α (EEEV, ZIKV, RVFV), and PTGS2 (EEEV, CHIKV, ZIKV). Additionally, inhibition of the inflammatory gene PTGS2 with Celecoxib, a small molecule inhibitor, rescued astrocytoma cells from VEEV-induced cell death but had no impact on viral titers. Collectively, these results suggest that EGR1 induction following viral infection stimulates multiple inflammatory mediators. Managing inflammation and cell death in response to viral infection is of utmost importance, especially during VEEV infection where survivors are at-risk for neurological sequalae.

A comprehensive review of viruses in terrestrial animals from the Caribbean islands of Greater and Lesser Antilles

Viruses pose a major threat to animal health worldwide, causing significant mortalities and morbidities in livestock, companion animals and wildlife, with adverse implications on human health, livelihoods, food safety and security, regional/national economies, and biodiversity. The Greater and Lesser Antilles consist of a cluster of islands between the North and South Americas and is habitat to a wide variety of animal species. This review is the first to put together decades of information on different viruses circulating in companion animals, livestock, and wildlife from the Caribbean islands of Greater and Lesser Antilles. Although animal viral diseases have been documented in the Caribbean region since the 1940s, we found that studies on different animal viruses are limited, inconsistent, and scattered. Furthermore, a significant number of the reports were based on serological assays, yielding preliminary data. The available information was assessed to identify knowledge gaps and limitations, and accordingly, recommendations were made, with the overall goal to improve animal health and production, and combat zoonoses in the region. This article is protected by copyright. All rights reserved.

Eastern Equine Encephalomyelitis in Michigan: Historical Review of Equine, Human, and Wildlife Involvement, Epidemiology, Vector Associations, and Factors Contributing to Endemicity

Eastern equine encephalomyelitis (EEE) is a mosquito-borne viral disease that is an emerging public health concern in the state of Michigan. Although Michigan has one of the highest incidence rates of EEE in the United States, much of the information known about cases in humans, equines, and other animals residing in Michigan is unpublished. This article summarizes such information and explores spatial trends in the historic distribution of EEE in Michigan. Outbreaks in Michigan have occurred over an 80-yr interval, involving only horses in 1942-1943 and 1973-1976, and then episodically from 1980 to 2020, and involving horses, humans, and wild and domestic animals. An estimated 1,036 equine cases (confirmed and suspected) and 36 confirmed human cases have occurred, including 10 in 2019 (6 deaths) and 4 in 2020 (2 deaths). Human cases ranged in age from 1 to 81 yr; 70% were male, and fatality rate of 34.3%. Equine and human cases occurred from July to October, peaked in August, and cluster in space in southwestern and southeastern lower Michigan. Cases occurred in glacial outwash and ice-contact landscapes in glacial interlobate zones. EEE virus (EEEV) was recovered from Culiseta melanura, Coquillettidia perturbans, five species of Aedes, and other mosquito species near horse and human case sites. Virus isolations or presence of neutralizing antibodies in several passerine species of birds suggest broad EEEV-bird associations. White-tailed deer and other wildlife were also affected. Geographic spread to northern areas of the state suggests expansion of this disease system into new and unsuspected foci.

The Complex Epidemiological Relationship between Flooding Events and Human Outbreaks of Mosquito-Borne Diseases: A Scoping Review

BACKGROUND

Climate change is expected to increase the frequency of flooding events. Although rainfall is highly correlated with mosquito-borne diseases (MBD) in humans, less research focuses on understanding the impact of flooding events on disease incidence. This lack of research presents a significant gap in climate change-driven disease forecasting.

OBJECTIVES

We conducted a scoping review to assess the strength of evidence regarding the potential relationship between flooding and MBD and to determine knowledge gaps.

METHODS

PubMed, Embase, and Web of Science were searched through 31 December 2020 and supplemented with review of citations in relevant publications. Studies on rainfall were included only if the operationalization allowed for distinction of unusually heavy rainfall events. Data were abstracted by disease (dengue, malaria, or other) and stratified by post-event timing of disease assessment. Studies that conducted statistical testing were summarized in detail.

RESULTS

From 3,008 initial results, we included 131 relevant studies (dengue n = 45 , malaria n = 61 , other MBD n = 49 ). Dengue studies indicated short-term (< 1  month ) decreases and subsequent (1-4 month) increases in incidence. Malaria studies indicated post-event incidence increases, but the results were mixed, and the temporal pattern was less clear. Statistical evidence was limited for other MBD, though findings suggest that human outbreaks of Murray Valley encephalitis, Ross River virus, Barmah Forest virus, Rift Valley fever, and Japanese encephalitis may follow flooding.

DISCUSSION

Flooding is generally associated with increased incidence of MBD, potentially following a brief decrease in incidence for some diseases. Methodological inconsistencies significantly limit direct comparison and generalizability of study results. Regions with established MBD and weather surveillance should be leveraged to conduct multisite research to a) standardize the quantification of relevant flooding, b) study nonlinear relationships between rainfall and disease, c) report outcomes at multiple lag periods, and d) investigate interacting factors that modify the likelihood and severity of outbreaks across different settings. https://doi.org/10.1289/EHP8887.

Mosquito Control Priorities in Florida-Survey Results from Florida Mosquito Control Districts

Florida lies within a subtropical region where the climate allows diverse mosquito species including invasive species to thrive year-round. As of 2021, there are currently 66 state-approved Florida Mosquito Control Districts, which are major stakeholders for Florida public universities engaged in mosquito research. Florida is one of the few states with extensive organized mosquito control programs. The Florida State Government and Florida Mosquito Control Districts have long histories of collaboration with research institutions. During fall 2020, we carried out a survey to collect baseline data on the current control priorities from Florida Mosquito Control Districts relating to (1) priority control species, (2) common adult and larval control methods, and (3) major research questions to address that will improve their control and surveillance programs. The survey data showed that a total of 17 distinct mosquito species were considered to be priority control targets, with many of these species being understudied. The most common control approaches included truck-mounted ultra-low-volume adulticiding and biopesticide-based larviciding. The districts held interest in diverse research questions, with many prioritizing studies on basic science questions to help develop evidence-based control strategies. Our data highlight the fact that mosquito control approaches and priorities differ greatly between districts and provide an important point of comparison for other regions investing in mosquito control, particularly those with similar ecological settings, and great diversity of potential mosquito vectors, such as in Florida. Our findings highlight a need for greater alignment of research priorities between mosquito control and mosquito research. In particular, we note a need to prioritize filling knowledge gaps relating to understudied mosquito species that have been implicated in arbovirus transmission.