First detection of Rio Negro virus (Venezuelan equine encephalitis complex subtype VI) in Córdoba, Argentina

Rio Negro virus (RNV) (Venezuelan equine encephalitis subtype VI) circulates only in Argentina; in northern provinces, isolates have been obtained from mosquitoes and rodents since 1980 and have been associated with acute febrile illness in humans. However, no studies of RNV have been performed in the central area of the country. We carried out molecular and serological detection of RNV in Córdoba, a province of the central part of the country, in mosquitoes and humans, respectively. One mosquito pool tested positive for alphavirus RNA by reverse transcriptase-nested polymerase chain reaction (RT-nested PCR). Subsequent sequencing determined that this alphavirus grouped with RNV. Serological studies detected antibodies to RNV in one human serum sample, which was obtained during the same period that RNV was detected using the aforementioned molecular methods. This is the first report of RNV circulation in the central area of Argentina, indicating an expansion of its original distribution. These results highlight the importance of strengthening surveillance procedures in endemic areas, as well as in new regions where RNV may emerge.

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

Estudio seroepidemiólogico de encefalitis por virus venezolano en la zona de Barlovento / Seroepidemiologic study of encephalitis due to Venezuelan virus in Barlovento zona

El presente trabajo describe el aislamiento de virus encefalomielítico equino, a partir de mosquitos colectados en el campo y su identificación en el laboratorio. El uso de animales centinelas y su seroconversión, demuestra la actividad viral vigente. El impacto de esta antroponosis en la población humana, está descrito mediante el estudio seroepidemiológico, observándose una positividad de 12% de las muestras tomadas