Historical, Epidemiological and Ecological Aspects of Arboviruses in Argentina: Flaviviridae, Bunyaviridae and Rhabdoviridae

RESUMO

This is a review of the arboviruses in Argentina belonging to families Flaviviridae, Bunyaviridae and Rhabdoviridae. Of the many viruses beloging to these families, the flavivirus St. Louis encephalitis (SLE), has been most intensively studies. 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 antibody 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 recognized. Possible explanations for this discrepancy include virus strain differences in virulence, ecologic factors determining the rate os virus transmission, and the lack of disease recognition and specific laboratory diagnosisof human meningoencephalitis. The transmission cycle of attenuated SLE virus strains isolated from rodents has not been studied. Ilheus virus has been isolated only once from a human being. The available serological data are difficult to interpret due to cross-reactivity with other flaviviruses, and the ecology and medical importance of this agent remain uncertain. Dengue has not been recognized in Argentina since 1916, although its vector, Aedes aegypti, was not eradicated 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 yet been reported, outbreaks of dengue in bordering countries (Brazil, Paraguay, Bolovia) since 1986, clearly signal that the country in once again at risk of importation and spread of the viruse