Simposio: Enferemedades transmitidas por mosquitos y otros dípteros

SIMPOSIO

Enfermedades transmitidas por mosquitos y otros dípteros

COORDINA: Raquel Gleiser & María Victoria Micieli

Enfermedades transmitidas por mosquitos y otros dípteros

El simposio aborda los arbovirus emergentes y reemergentes transmitidos por dípteros que afectan a América Latina. La discusión incluirá el reciente brote del virus Oropouche en Brasil, sus vectores primarios, los factores que contribuyen a su propagación y el potencial de expansión futura. La reemergencia de la encefalitis equina del Oeste en Argentina y Uruguay será analizada en el contexto de los cambios ambientales y epidemiológicos. Además, se presentará el conocimiento actual sobre la eco-epidemiología de la encefalitis de Saint Louis, el virus del Nilo Occidental y otros arbovirus transmitidos por mosquitos en América del Sur. Los ponentes analizarán las tendencias del virus del dengue, enfocándose en su situación actual y las perspectivas futuras en América Latina. A través de una revisión integral de la bioecología de los vectores, los patrones epidemiológicos y las implicancias en la salud pública, el simposio tiene como objetivo ofrecer una visión profunda de la dinámica de estas enfermedades y su impacto en la salud humana y animal.

Palabras clave: Mosquitos, arbovirus, salud pública.

Oropouche Virus Spread Beyond the Amazon: Genomic Characterization and Ecological Contexts

GRÄF, Tiago 1

1 Laboratorio de Virologia Molecular, Instituto Carlos Chagas, Fundacao Oswaldo Cruz, Curitiba, Brazil
E-mail address: tiago.graf@fiocruz.br

Oropouche virus (OROV) is an arbovirus endemic in the Amazon region that closely resembles other arboviruses in terms of human disease, leading to potential misdiagnoses. The virus ecology has mostly restricted its occurrence to the Amazon biome; however, after a large 2023–24 OROV epidemic in the Brazilian Amazon region, outbreaks are being reported across Brazil and in other countries in Latin America. Genomic analyses have shown that the virus causing the recent outbreaks is a recombinant form, resulting from a process of reassortment of genomic segments of OROV strains circulating in Brazil and other South American countries. Further studies are needed to clarify whether this new strain has greater replicative and infectious potential, since to date, only two studies have been published, showing contradictory results. Epidemic data show that outside the Amazon region, OROV cases frequency was four times higher in small municipalities than in large municipalities. The planted areas of some agricultural products, such as banana plantations, were positively correlated with OROV cases. The phylogenetic analysis of OROV genomes revealed multiple exportation events of the newly identified reassortant lineage from the Amazon to other Brazilian regions between January and March, 2024. At least three of the previously described OROV phylogenetic clades circulating in the Amazon were the source of viral introductions. Molecular clock analysis estimated that viral introductions happened from 50 days to 100 days before detecting the outbreaks in each state.  Our results confirm that the novel OROV reassortant lineage spread from the Amazon to other regions in early 2024, successfully establishing local transmission. The fact that outbreaks were observed in small municipalities, instead of large urban centers, suggests that local ecological conditions that are ideal for OROV vector occurrence, such as the banana plantation environment, might be important factors driving its spread in Brazil.

Keywords: Oropouche virus, genomic surveillance, phylogeny.

Current situation of dengue and other arboviruses transmitted by Aedes aegypti in Brazil

BRAGA, IA¹,²,³

¹ Latin American Network for Vector Control (RELCOV), Brazil
² Laboratory of Reference in Triatomines and Chagas Disease Epidemiology – Instituto René Rachou – Fiocruz/MG, Brazil
³ Professional Master’s Program in Surveillance and Vector Control – Instituto Oswaldo Cruz – Fiocruz/RJ, Brazil
E-mail address: relcov01@gmail.com

Arboviruses transmitted by Aedes aegypti represent a persistent and evolving public health challenge in Brazil. Dengue reemerged in the 1980s and rapidly became endemic, with recurrent epidemics driven by the successive introduction and co-circulation of all four dengue virus serotypes. Chikungunya was first confirmed in the country in 2014, followed by Zika virus in 2015, both spreading rapidly and triggering major health emergencies, including the Zika-associated microcephaly crisis. Since then, Brazil has experienced overlapping transmission of these three viruses in urban settings, with varying intensity.
The national spread of Aedes aegypti has played a central role in this scenario. Although initially more prevalent in tropical and subtropical areas, the mosquito is now present in all Brazilian states and in over 90% of municipalities, including medium and high-altitude urban centers previously considered unsuitable for its establishment. Environmental degradation, rapid and unplanned urbanization, water storage practices, and climate variability have favored its expansion and persistence, particularly in peri-urban and vulnerable areas.
In 2023, the country recorded approximately 1.6 million probable cases of dengue. In 2024, this number rose sharply, reaching a historic peak of over 6.8 million cases and nearly 2,900 deaths. This unprecedented epidemic was marked by the co-circulation of all four dengue virus serotypes (DENV‑1 to DENV‑4).
In 2025, a significant decline in dengue incidence was observed. By May, the Ministry of Health reported around 1.46 million probable cases, representing a 70% decrease compared to the same period in 2024. However, transmission remains widespread, and the continued presence of multiple serotypes poses a risk for new waves of severe dengue.
Chikungunya followed a similar pattern. After reporting 204,000 cases in 2023, Brazil faced over 420,000 cases in 2024, with approximately 141,000 cases reported through May 2025. Zika virus transmission remained low, with around 9,000 cases in 2023, 11,000 in 2024, and only 2,500 by March 2025.
To address these challenges, Brazil has intensified integrated vector control strategies, including source reduction, insecticide application, and the release of Aedes aegypti infected with Wolbachia. Community engagement and national awareness campaigns have also been reinforced. However, persistent environmental and social vulnerabilities, along with climate variability, continue to demand innovative, sustained, and multisectoral responses.

Keywords: Dengue, chikungunya, Zika, Aedes aegypti, arboviruses, Brazil

Echoes From The Past: Integrating Historical Data and Modern Insights into the Ecology of Equine Encephalitis by Arboviruses in Argentina

DIAZ, Adrián1

1 Laboratorio de Arbovirus, Institute of Virology “Dr. J. M. Vanella”, Faculty of Medical Sciences, National University of Cordoba. Córdoba, Córdoba, Argentina.
E-mail address: adrian.diaz@fcm.unc.edu.ar

The emergence and re-emergence of mosquito-borne arboviruses remains a pressing issue in Argentina and throughout the region. In recent years, Argentina has faced the introduction of West Nile virus (WNV), the emergence of orthobunyaviruses and the re-emergence of Western equine encephalitis virus (WEEV)—all of them posing risks to both animal and human health. In this presentation, I will provide an ecological characterization of hosts and vectors involved in the transmission of these viruses, integrating historical knowledge with recent data from field and laboratory studies. Emphasis will be placed on novel findings related to mosquito vectors in the latest WEEV epizootic, including the detection of UNA virus—an overlooked alphavirus with known pathogenicity in horses and historical circulation in the region. An integrated analysis of ecological, environmental, and molecular data suggests that environmental change, meteorological conditions, land-use modification, and the potential introduction of viruses via migratory birds could be contributing drivers of these emergence events.By combining classical surveillance records, modern molecular diagnostics, and ecological insights, I aim to highlight key environmental and biological factors that may be driving the emergence of these viruses. Understanding these patterns is critical to anticipating future outbreaks and designing effective, integrated surveillance strategies. This talk will reflect on how historical data—often underutilized—can be instrumental when contextualized with contemporary findings, and how interdisciplinary approaches are necessary to grasp the complexity of arbovirus ecology in dynamic landscapes.

Keywords: Equine encephalitis, Vectors, Arbovirus.

Epizootic outbreak of WEE virus in Uruguay: Strengths of inter-institutional collaboration.

FRABASILE, Sandra1, MOREL, Noelia2, PÉREZ, Ramiro3, MOREIRA MARRERO, Lucía1, BURGUEÑO, Analía2, CORTINAS, Ma. Noel4, BASSETTI, Lucía3, NEGRO, Raúl3, RODRÍGUEZ, Sirley3, BÓRMIDA, Victoria4, GAYO, Valeria3, COSTA DE SOUZA, Víctor5, GOMES NAVECA, Felipe5,6, MARTÍNEZ GÓMEZ, Mariela7, GRESH, Lionel7, MENDEZ-RICO, Jairo7, CHIPARELLI, Héctor2, DELFRARO, Adriana1.

1 Sección Virología, Facultad de Ciencias, Universidad de la República, Montevideo, Uruguay.
2 Unidad de Virología, Departamento de Laboratorios de Salud Pública (DLSP), Ministerio de Salud Pública, Montevideo, Uruguay.
3 División de Laboratorios Veterinarios (DILAVE), Dirección General de Servicios Ganaderos (DGSG), Ministerio de Ganadería Agricultura y Pesca, Montevideo (MGAP), Uruguay.
4 Laboratorio de Genómica, Departamento de Laboratorios de Salud Pública (DLSP), Ministerio de Salud Pública, Montevideo, Uruguay
5 Núcleo de Vigilância de Vírus Emergentes, Reemergentes ou Negligenciados – ViVER/EDTA. Instituto Leônidas e Maria Deane, Fiocruz, Manaus, AM, Brazil.
6 Laboratório de Arbovírus e Vírus Hemorrágicos, Instituto Oswaldo Cruz, Fiocruz, Rio de Janeiro, RJ, Brazil.
7Infectious Hazards Management Unit, Health Emergencies Department, Pan-American Health Organization, Washington D.C., USA
E-mail address: adriana@fcien.edu.uy

In November 2023 an outbreak of equine encephalomyelitis in horses was reported in Western Uruguay, concomitantly with an outbreak initiated in the Argentinean provinces of Corrientes and Santa Fe. On 5th December, Western Equine encephalitis virus (WEEV) was laboratory confirmed as the causative agent, in a dead horse from Salto Department. Up to March 2024 the outbreak extended all along the country. The most recent reports of WEEV in the region were a PRNT-seropositive horse collected in 2007, and a fatal human case reported in 2009, both in Uruguay. In North America, there are no reports of equine or human WEEV cases since 1998. 
The rapid identification of the virus was achieved thanks to an interinstitutional collaboration between the health authorities and the academia. Homogenates of brain tissue samples and cerebrospinal fluid were subjected to nucleic acid extraction. Diagnosis was done using a RT-nested PCR targeted on the nsp4 gene, followed by Sanger sequencing and phylogeny. Complete genomes from six samples were obtained by hybrid–capture enrichment Miseq Illumina NGS using the Viral Surveillance Panel from Illumina®. 
Maximum likelihood phylogenetic analysis showed that Uruguayan sequences form a monophyletic group in the WEEV clade, together with Brazilian genomes from the outbreak and group independently from the North American sequences. The outbreak sequences were closely related to an old Argentinean virus isolated from a sick horse in 1950. Two additional Argentinean sequences isolated from a Culex spp mosquito (1980) and a horse (1933) were related to the epizootic clade. The old Uruguayan sequence retrieved from the 2009 case was unrelated to the outbreak and clusters together with USA sequences. The origin and spreading of this outbreak are intriguing but are probably influenced by a highly rainy season and extensive floodings occurred in the previous months, followed by intense mosquito proliferation, specially of the “flooding mosquito” Aedes albifasciatus. Field work is undergoing to identify the amplifying vertebrate hosts and the mosquito species acting as vectors.

Keywords: WEEV, equine, genomics

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Aedes dorsalis, imagen por bradenjudson, CC 1.0, Wikimedia Commons (https://commons.wikimedia.org/wiki/File:Aedes_dorsalis.png) | Las imágenes de las personas miembro de los distintos comités de LA SOVE RELCOV 2025 así como las imágenes de los/as oradores/as fueron provistas por las mismas personas para uso exclusivo en esta página web. Los/as autores/as de estas imágenes se reservan el derecho de uso y reproducción de las mismas.

Cronograma del evento (1)

Viernes 24
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