Genomic Characterization and Seroprevalence Studies on Alphaviruses in Uruguay

Effects of climate change on the occurrence and distribution of Western equine encephalitis virus in South America

OBJECTIVES

The Western equine encephalitis virus (WEEV) is a globally relevant vector-borne pathogen that causes encephalitis. The role of environmental variables in the epidemiology of WEEV has become greater in the context of climate change. In December 2023, a significant resurgence of WEEV began in South America, with major ongoing outbreaks in Argentina and Uruguay. In this study, we employed a machine learning algorithm to model the distribution of WEEV in South America, considering both present and future scenarios.

STUDY DESIGN

Ecological retrospective study.

METHODS

We conducted a modelling study to identify areas with the highest prevalence of WEEV in South America, based on confirmed human and equine cases during the 2023/2024 outbreak and climatic variables. Our analysis utilised Maxent software, a machine learning algorithm for species distribution modelling.

RESULTS

Our results indicate that environmental variables, particularly thermal seasonality and annual rainfall, can directly influence the occurrence of WEEV, leading to increased virus incidence. Consequently, high-risk areas may shift in the future. Countries, such as Paraguay, Venezuela, Colombia, and various regions in Brazil, particularly the Northeast, Midwest, and the Pantanal biomes, will be significantly impacted, drastically altering the current distribution of WEEV.

CONCLUSIONS

The ongoing WEEV outbreak in South America is concerning because it coincides with migratory bird stopovers. These birds are natural hosts that can spread the virus to unaffected areas. Our results will help to identify priority areas for developing preventive measures and establishing epidemiological surveillance.

Equine Encephalomyelitis Outbreak, Uruguay, 2023-2024

We report the genomic analysis from early equine cases of the Western equine encephalitis virus outbreak during 2023-2024 in Uruguay. Sequences are related to a viral isolate from an outbreak in 1958 in Argentina. A viral origin from South America or continuous enzootic circulation with infrequent spillover is possible.

Diagnosis and genomic characterization of the largest western equine encephalitis virus outbreak in Uruguay during 2023-2024

The Western equine encephalitis virus is transmitted between mosquitoes and wild birds. Mosquitoes spread the virus to horses and human populations, causing severe encephalitis and death. The most recent large outbreak occurred in South America from November 2023 to April 2024. We identified and genetically characterized Uruguayan strains during this outbreak to understand their evolutionary trends and rapid expansion. We obtained genomes from 15 strains using a novel multiplex PCR assay combined with next-generation Illumina sequencing. The phylogenetic analysis revealed that viruses from Uruguay and Brazil collected during the outbreak and an Argentine strain from 1958 share a common evolutionary origin and are distinct from North American strains. Phylogenetic and epidemiological data suggest that the outbreak originated in Argentina and spread to Uruguay and Brazil, likely by movements of infected birds. Genomic analysis also revealed mispairing in real-time PCR primers and probes that may affect official diagnostic protocols.

Rio Negro Virus Infection, Bolivia, 2021

In May 2021, an agricultural worker originally from Trementinal, Argentina, sought treatment for febrile illness in Tarija, Bolivia, where he resided at the time of illness onset. The patient tested negative for hantavirus RNA, but next-generation sequencing of a serum sample yielded a complete genome for Rio Negro virus.

Understanding host responses to equine encephalitis virus infection: implications for therapeutic development

INTRODUCTION

Venezuelan, eastern, and western equine encephalitis viruses (VEEV, EEEV, and WEEV) are mosquito-borne New World alphaviruses that cause encephalitis in equids and humans. These viruses can cause severe disease and death, as well as long-term severe neurological symptoms in survivors. Despite the pathogenesis and weaponization of these viruses, there are no approved therapeutics for treating infection.

AREAS COVERED

In this review, we describe the molecular pathogenesis of these viruses, discuss host-pathogen interactions needed for viral replication, and highlight new avenues for drug development with a focus on host-targeted approaches.

EXPERT OPINION

Current approaches have yielded some promising therapeutics, but additional emphasis should be placed on advanced development of existing small molecules and pursuit of pan-encephalitic alphavirus drugs. More research should be conducted on EEEV and WEEV, given their high lethality rates.

Alphavirus Identification in Neotropical Bats

Alphaviruses (Togaviridae) are arthropod-borne viruses responsible for several emerging diseases, maintained in nature through transmission between hematophagous arthropod vectors and susceptible vertebrate hosts. Although bats harbor many species of viruses, their role as reservoir hosts in emergent zoonoses has been verified only in a few cases. With bats being the second most diverse order of mammals, their implication in arbovirus infections needs to be elucidated. Reports on arbovirus infections in bats are scarce, especially in South American indigenous species. In this work, we report the genomic detection and identification of two different alphaviruses in oral swabs from bats captured in Northern Uruguay. Phylogenetic analysis identified Río Negro virus (RNV) in two different species: Tadarida brasiliensis (n = 6) and Myotis spp. (n = 1) and eastern equine encephalitis virus (EEEV) in Myotis spp. (n = 2). Previous studies of our group identified RNV and EEEV in mosquitoes and horse serology, suggesting that they may be circulating in enzootic cycles in our country. Our findings reveal that bats can be infected by these arboviruses and that chiropterans could participate in the viral natural cycle as virus amplifiers or dead-end hosts. Further studies are warranted to elucidate the role of these mammals in the biological cycle of these alphaviruses in Uruguay.

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

Background: Eastern equine encephalitis virus (EEEV) is a mosquito-borne virus that is primarily found in North America and the Caribbean. Over the past decade there has been an increase in virus activity, including large outbreaks in human and horse populations. Predicted climate change is expected to affect the range of mosquitoes including vectors of EEEV, which may alter disease risk posing a public health concern. Methods: A scoping review (ScR) was conducted to identify and characterize the global evidence on EEEV. A thorough search was conducted in relevant bibliographic databases and government websites. Two reviewers screened titles and abstracts for relevance and the characteristics of relevant articles were extracted using a uniformly implemented data collection form. The study protocol was developed a priori and described the methods and tools used and this article follows the PRISMA-ScR guidelines for reporting ScRs. Results: The ScR included 718 relevant research articles. The majority of the articles originated from North America (97%) between 1933 and 2019. EEEV has been identified in 35 species of mosquitoes, over 200 species of birds, various domestic animals, wild mammals, reptiles, and amphibians. Articles identified in this ScR primarily covered three topic areas: epidemiology of hosts and vectors (344 articles) including surveillance results (138), pathogenesis of EEEV in hosts (193), and in vitro studies characterizing EEEV (111). Fewer articles evaluated the accuracy of diagnostic tests (63), the efficacy of mitigation strategies (62), transmission dynamics (56), treatment of EEEV in hosts (10), societal knowledge, attitudes, and perceptions (4), and economic burden (2). Conclusion: With the projected impact of climate change on mosquito populations, it is expected that the risk of EEEV could change resulting in higher disease burden or spread into previously unaffected areas. Future research efforts should focus on closing some of the important knowledge gaps identified in this ScR.

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.

Equine viral encephalitis: prevalence, impact, and management strategies

Members of several different virus families cause equine viral encephalitis, the majority of which are arthropod-borne viruses (arboviruses) with zoonotic potential. The clinical signs caused are rarely pathognomonic; therefore, a clinical diagnosis is usually presumptive according to the geographical region. However, recent decades have seen expansion of the geographical range and emergence in new regions of numerous viral diseases. In this context, this review presents an overview of the prevalence and distribution of the main viral causes of equine encephalitis and discusses their impact and potential approaches to limit their spread.