Reemergencia de la encefalitis equina del oeste (WEEV) en la Argentina: una revisión de aspectos epidemiológicos, virológicos y clínicos de relevancia / Reemergence of western equine encephalitis in Argentina

La encefalitis equina del oeste (WEEV, por su sigla en inglés, Western Equine Encephalitis) es una enfermedad reemergente en Argentina a partir del año 2023. La co-municación inicial fue en 1933, las últimas epizootias ocurrieron en 1983 y el último caso humano se registró en 1996. Se revisan las características del agente causal, la ecología con especial referencia a los vectores iden-tificados en el país, su competencia en la transmisión y el ciclo así como los factores de riesgo para adquirir la enfermedad. La situación epidemiológica en equinos y humanos desde noviembre 2023 hasta marzo 2024 es analizada. Se describen las formas clínicas de presen-tación de la enfermedad humana, las posibilidades evo-lutivas, los datos disponibles en los casos confirmados y el tratamiento. La metodología y algoritmo empleados para el diagnóstico etiológico en el Centro Nacional de Referencia son detallados. Las estrategias para la pre-vención y el control se basan en la vacunación de los equinos, el saneamiento ambiental y el control del foco ante la presentación de la enfermedad animal (vigilancia epidemiológica activa)

Western equine encephalitis (WEE) is a re-emerging dis-ease in Argentina starting in 2023. Since the initial notifi-cation in 1933, the last epizootics occurred in 1983, and the last human case was recorded in 1996.The charac-teristics of the causative agent, the ecology with special reference to vectors identified in the country, their compe-tence in transmission, and the cycle as well as the risks factors for acquiring the disease, are reviewed.The epidemiological situation in horses and humans from November 2023 to March 2024 is analyzed. The clinical presentation of the human disease, its evolutionary po-tential, available data in confirmed cases, and the treat-ment are described.The methodology and algorithm used for the etiological diagnosis at the National Reference Center are detailed. Strategies for prevention and control are based on vaccination of horses, environmental sani-tation and outbreak control in the presence of the animal disease (active epidemiological surveillance)

Protocolo del Sistema Nacional de Vigilancia Epidemiológica: enfermedades zoonóticas. No. 08 / Protocol of the National Epidemiological Surveillance System: zoonotic diseases. No. 08

Estos protocolos están dirigido a personal médico, paramédico y otros profesionales que realizan acciones gerenciales y operativas de vigilancia epidemiológica en los servicios de salud del país, y están divididos en varios tomos para dar a conocer y actualizar la identificación y medidas de control para diversos padecimientos a fin de continuar con el mejoramiento de las capacidades técnicas de los trabajadores de salud, que permita planificar la prestación de servicios con decisiones partiendo de un enfoque epidemiológico comprobado, para responder a los cambios de tendencias epidemiológicas y con ello contribuir al fortalecimiento de prácticas asertivas de la salud pública de nuestro país.

Prevalence of antibodies to equine alphaviruses in the State of Pará, Brazil / Prevalência de anticorpos para alphavirus em equinos do estado do Pará, Brasil

The State of Pará comprises 26% of Brazilian Amazon region, where a large diversity of arboviruses has been described. This study sought to assess the prevalence and distribution of hemagglutination inhibition (HI) antibodies against antigens of four alphaviruses (Togaviridae: Alphavirus ) from the species: Eastern equine encephalitis (EEEV), Western equine encephalitis (WEEV), Mayaro virus (MAYV), and Mucambo virus (MUCV) in 753 serum samples of horses in Pará State, Brazil. All investigated arboviruses were detected and indicate that horses are susceptible to these alphaviruses, and show evidences of their active circulation in farm animals in the Brazilian Amazon.(AU)

O estado do Pará corresponde a 26% da Amazônia brasileira, onde uma grande diversidade de arbovírus foi descrita. Este estudo procurou avaliar a prevalência e a distribuição de anticorpos inibidores da hemaglutinação (IH) contra antígenos de quatro alfavirus (Togaviridae: Alphavirus ), das espécies: Vírus da encefalite equina do leste (EEEV), Vírus da encefalite equina do oeste (WEEV), Vírus mayaro (MAYV) e Vírus mucambo (MUCV), de 753 amostras de soro de equinos no estado do Pará, Brasil. Todos os arbovirus pesquisados foram detectados, indicando que os equinos são suscetíveis a esses Alphavirus e mostrando evidências de sua circulação ativa em animais de fazenda na Amazônia brasileira.(AU)

Zoonotic encephalitides caused by arboviruses: transmission and epidemiology of alphaviruses and flaviviruses

In this review, we mainly focus on zoonotic encephalitides caused by arthropod-borne viruses (arboviruses) of the families Flaviviridae (genus Flavivirus) and Togaviridae (genus Alphavirus) that are important in both humans and domestic animals. Specifically, we will focus on alphaviruses (Eastern equine encephalitis virus, Western equine encephalitis virus, Venezuelan equine encephalitis virus) and flaviviruses (Japanese encephalitis virus and West Nile virus). Most of these viruses were originally found in tropical regions such as Africa and South America or in some regions in Asia. However, they have dispersed widely and currently cause diseases around the world. Global warming, increasing urbanization and population size in tropical regions, faster transportation and rapid spread of arthropod vectors contribute in continuous spreading of arboviruses into new geographic areas causing reemerging or resurging diseases. Most of the reemerging arboviruses also have emerged as zoonotic disease agents and created major public health issues and disease epidemics.

Apuntes para el desarrollo de sistemas de vigilancia para la detección precoz del Virus del Oeste del Nilo / Notes on the development of surveillance systems for West Nile virus early detection

A finales de 1999 se presentaron en los Estados Unidos los primeros casos humanos producidos por el Virus del Oeste del Nilo, el cual circulaba tan solo en el norte de África, Oriente Medio, el Cáucaso, los Balcanes y la cuenca Mediterránea. Luego de su aparición se ha extendido en dos años a la mitad occidental de los Estados Unidos, Canadá y algunas islas del Caribe, por lo se espera se disemine por todo el continente ya que su principal reservorio son las aves incluyendo las migratorias. En este artículo se revisan los elementos fundamentales que se han descubierto de esta nueva epidemia, así como las recomendaciones actuales sobre sistemas de vigilancia del virus

Historical, epidemiological and ecological aspects of arboviruses in Argentina: Togaviridae, Alphavirus

This is a review of the arboviruses in Argentina belonging to families Flaviridae, Bunyaviridae and Rhabdoviridae. Of the many viruses belonging to these families, the flavivirus St. Louis encephalitis (SLE), has been most intensively studied. SLE virus strains have been recovered from three sources: 2 strains from humans with an undifferentiated, febrile disease; 6 from mosquitoes; and 2 from rodents. The viruses recovered from rodents are attenuated and those from mosquitoes are virulent based on a neuroinvasiveness test in mice; the degree of virulence of the mosquito strains remain to be analyzed. Serological surveys indicate a wide distribution and endemicity of SLE virus in the temperate and subtropical areas (central and northern Argentina), but no data are available from the andean region or from the South. The virulent SLE virus strains appear to be transmitted between Culex (Cx.)spp. from which they were isolated, and wild birds, based on antobody prevalence. A urban cycle may involve Cx. quinquefasciatus (source of a viral isolate and a competent experimental vector) and abundant birds (house sparrows, doves, and/or chickens), chickens are experimentally competent host species. Despite similarities in the ecology of SLE between Argentina and North America, urban outbreaks of SLE have not been recognized. Possible explanations for this discrepancy include virus strain differences in virulenc, ecologic factors determining the rate of virus transmission, and the lack of disease recognition and specific laboratory diagnosis of human meningoencephalitis. The transmission cycle of attenuated SLE virus strains isolated from rodentshas not been studied. Ilheus virus has isolated only once from a human being. The available serological data are difficult to interpret due to cross-reactivity with other flaviviruses, and the ecologyand medical importance of this agent remain uncertain. Dengue has not been recognized in Argentina since 1916, although is vector, Aedes aegypti, was not erradicated until 1963. Dengue was previously present in coastal localities of Chaco. Corrientes and Misiones Provinces. Within the last few years, Argentina was reinfested by Ae. aegypti. Although no human cases have vet been reported, outbreaks of dengue in bordering countries (Brazil, Paraguay, Bolivia) since 1986, cleary signal that the country in once againat risk of importantion ans spread of the virus

Effects of ultraviolet radiation on structural components of enveloped RNA viruses

The interaction of ultraviolet radiation and virus particles of Western Equine Encephalomyelitis Virus (WEE) and Newcastle Disease Virus (NDV) which have respectively RNA of positive (RNA+) and negative (RNA-) polarity as genomes, was studied using purified particles. The purified virus preparations were irradiated at a range from 1,000 to 6,000 joules per m2 with posterior analysis of their propagation in primary cell cultures of chicken embryos. It could be observed that a radiation dose of to 4,500 joules per m2 could induce 10(9) TCID50 per ml as minimal loss of titer for WEE virus and NDV. The hemagglutination assay was used as a toll to evaluate the alterations caused by UV radiation on the molecular arrangement of virus proteins. Alterations of the virus hemagglutinating activity were only observe when radiation levels higher than 6,000 joules per m2 were used. The results from hemolysis assays showed the importance of the loss of the envelope integrity and the damages to nucleoprotein structures during the inactivation process, when we used radiation doses higher than 6,000 joules per m2. This model of study can increase our comprehension of the radiation effects on the cell physiology and biological components of the cell membranes.

Effects of low pH on hemagglutinating and hemolytic activities of west equine encephalomyelitis virus

1. The hemagglutinating (HA) and hemolytic (HL) activities mediated by egg-propagated west equine encephalomyelitis (WEE) virus preparations were investigated. 2. The purified virus preparation exhibited the best HA and HL activity at pH 6.0 and 6.0-6.2, respectively, as observed in the HA and HL tests. 3. In the virus preparations, both HA and HL activities were completely lost upon pretreatment at low pH (6.0). 4. The present results suggest that the alphavirus-mediated HA and HL activities against chicken erythrocytes can be considered to be a fusion from without

Peroral susceptibility of Aedes alblifasciatus and Culex pipiens complex mosquitoes (Diptera: Culicidae) from Argentina to western equine encephalitis virus

The transmission cycle of western equine encephalitis (WEE) virus in South America is unknown. A WEE virus strain was isolated from Aedes albifasciatus in Argentina during the WEE epizootic of 1982-83. Also, Culex pipiens from Argentina was reported to be able to transmit WEE virus experimentally, but other results indicate that Cx. pipiens from the USA is refractory to this virus. We determined the susceptibility of Argentina strains of Ae. albifasciatus and Culex pipiens complex mosquitoes to infection by WEE virus by the oral route. Adult females were fed on chicks infected with a WEE virus strain isolated in Cordoba Province, Argentina, or were fed on a blood/virus suspension. Each mosquito ingested between 10(1.6) to 10(6.4) vero cell plaque-forming units of virus. Each of 28 Ae. albifasciatus was positive for virus from the fourth day postfeeding, and there was evidence for virus replication. In contrast, 0/44 Cx. p. quinquefasciatus and only 1/15 Cx. p. pipiens was positive. Aedes albifasciatus is susceptible to infection by WEE virus and should be considered a potential vector of this virus in Argentina. Both subspecies of Cx.pipiens are refractory to peroral infection by WEE virus and probably do not play a role in the WEE virus cicle in Argentina

Anticuerpos contra el virus de la encefalitis equina venezolana en la población humana del Distrito Mara del Estado Zulia. Venezuela / Antibodies against venezuelan equine encephalitis virus in the human population of Distrito Mara Estado Zulia. Venezuela

Con el propósito de conocer la presencia de anticuerpos contra el virus de la Encefalitis Equina Venezolana, en la población humana del Distrito Mara, Estado Zulia, Venezuela, se tomaron entre junio, julio y septiembre de 1988, 239 muestras de sangre. Estas provenían de las poblaciones de San Rafael de Mara (78), Santa Cruz de Mara (69), Carrasquero (33), 4 Bocas-La Sierrita (33), Isla de San Carlos (7) e Isla de Toas (19). Las muestras fueron ordenadas de acuerdo al sexo y edad. De los sujetos estudiados, 89 fueron menores de 15 años y 150, de 15 años y más. Utilizando el método de inhibición de la hemaglutinación, se encontró que del total de muestras, 224 resultaron negativas, representando un 93,7%. Quince tuvieron títulos superiores a 1:20, lo que representó solo un 6,3% de positividad. De estos resultados se desprende que la mayoría de la población estudiada no tenía anticuerpos contra el vitus de la Encefalitis Equina Venezolana, sobre todo los niños nacidos después de la última epidemia ocurrida en 1973, lo cual representa un alerta sobre la situación inmunológica de la población de este Distrito en relación a este virus, y que en cualquier momento puede originarse una nueva epidemia

Partial purification of western equine encephalitis virus by fractionation procedures.

Concentracao, purificacao parcial e fracionamento do virus da encefalite equina do oeste (WEE) foram realizados pelos processos de precipitacao com sulfato de amonia e centrifugacao a alta velocidade. As hemaglutininas foram achadas nas fracoes de antigenos soluveis obtidos, pela precipitacao com solucao de sulfato de amonio, nas concentracoes de 30, 40 e 50 porcento.Os antigenos do tipo de fixacao de complemento foram achados, tanto nas fracoes de antigenos soluveis, como nas preparacoes contendo os antigenos precipitados. Pelo menos dois antigenos do tipo precipitinas foram determinados nas fracoes precipitadas pelas solucoes de sulfato de amonia, nas concentracoes de 70 e 80%. As fracoes correspondentes a concentracao de sulfato de amonia nos valores 40 e 50 porcento apresentaram a maior reatividade nas reacoes de fixacao complemento (FC), hemaglutinacao (HA) e imunodifusao (ID)