West Nile Virus in Argentina : a new emerging infectious agent raising new challenges

El virus West Nile es un flavivirus patógeno para humanos en el Viejo Mundo que ha experimentado recientemente un proceso de emergencia en el continente americano. Desde su introducción en 1999 en EEUU, se ha convertido en un patógeno de preocupación para las poblaciones de aves silvestres al haber provocado allí eventos masivos de mortalidad y porque numerosas especies de aves han experimentado disminuciones significativas de sus poblaciones. Para 2001 el virus ya se había dispersado fuera de EEUU, extendiéndose por América del Sur, América Central y el Caribe. Debido a la falta de un sistema de vigilancia activo para esta patología, no se conoce su verdadero impacto sobre las poblaciones silvestres en esas regiones. Sin embargo, la ausencia de epizootias indica una marcada diferencia en el comportamiento epidemiológico del virus con respecto a EEUU. En Argentina, su ecoepidemiología está poco estudiada y ha recibido poca atención en el ámbito ornitológico. Existen antecedentes de aislamiento viral en equinos enfermos y muertos, casos febriles y de encefalitis en humanos y detección de anticuerpos en aves silvestres en provincias del centro y norte del país. En este trabajo se brinda un análisis actualizado de la situación ecoepidemiológica del virus West Nile, aclarando conceptos básicos de virología y epidemiología para generar un acercamiento e interés de los ornitólogos en el área de los patógenos de importancia para la conservación de las aves. Hace falta una mayor inversión y participación en actividades de investigación interdisciplinarias para aclarar aspectos básicos de la biología, ecología y epidemiología de este nuevo patógeno en el continente americano.The West Nile virus, a human pathogen flavivirus, has recently shown an emerging process through the American continent. Since its introduction in 1999 into the United States, it became a concerned pathogen for wild bird populations, because of massive bird deaths events and significant bird population declines. By 2001 the virus has reached countries in South America, Central America and the Caribbean. The true role of this virus as pathogen for wild birds there is unknown, mainly due to the lack of active surveillance systems. Notwithstanding, there is no epizootic event reported yet, in contrast with the epidemiological behaviour of the virus in the United States. In Argentina, its ecoepidemiology is mostly unknown and it has received little attention from ornithologists. There are reports of viral isolations from dead equines, encephalitis and febrile human cases, as well as neutralizing antibodies detections in wild birds in central and northern provinces. In this review we provide an updated analysis regarding the ecoepidemiology of West Nile virus, and we give basic insights related to basic virological and epidemiological concepts in order to call the attention of ornithologists on the relationship between pathogens and bird conservation. Stronger support on interdisciplinary scientific projects is necessary to provide insight into the biology, ecology and epidemiology of this new viral pathogen in the American continent

Incidence of the nordihydroguaiaretic acid content on the in vitro antiviral activity of extracts obtained from larrea divaricata cav. (Zygophyllaceae)

The South American species Larrea divaricata Cav. (Zygophyllaceae) has been widely used in folk medicine against infectious diseases. In previous studies, we reported that several extracts obtained from the aerial parts of this species and the nordihydroguaiaretic acid (NDGA), its main lignan, inhibited Junin Virus (JUNV) in vitro. In this work, the objective was to assess whether NDGA is truly responsible for the antiviral activity produced by the extracts. Therefore, the presence and amount of NDGA in extracts were determined by HPLC. We established that NDGA in the extracts analyzed is required to inhibit JUNV and observed that some components of the bioactive extracts would increase the antiviral effect of NDGA. On the other hand, we estimated the selectivity index for NDGA against JUNV. Thus, NDGA and extracts containing this lignan exhibited potential therapeutic effects against the etiologic agent of the Argentine Hemorrhagic Fever, an endemo-epidemic illness in this country.Colegio de Farmacéuticos de la Provincia de Buenos Aire

Determination of non-toxic and subtoxic concentrations of potential antiviral natural anthraquinones

Anthraquinones-rich extracts of Heterophyllaea pustulata Hook f. (Rubiaceae) exhibited in vitro antiviral activity against Herpes Simplex Virus Type I, from which several anthraquinones (AQs) were isolated and identified. The Maximum Non-Cytotoxic Concentration (MNCC), the subtoxic concentration (SubTC), and the CC50 of each AQ were determined on a mammalian eukaryotic cell line (Vero cells) by means of Neutral Red uptake assay; the cytopathic effect was simultaneously evaluated by optical microscopy. The range of concentrations where each AQ did not exhibit cytotoxicity was established, which is limited by the MNCC: rubiadin 1-methyl ether, damnacanthol and pustuline were found to be markedly less cytotoxic. To the remaining AQs, we could estimate a SubTC (about 10 μg/mL) that assures 80 % cellular viability. Therefore, we determined a concentration range which could be used to evaluate the antiviral effect of each AQ since it ensures the viability of the host cell.Colegio de Farmacéuticos de la Provincia de Buenos Aire

Phylodynamics of Hepatitis C Virus Subtype 2c in the Province of Córdoba, Argentina

The Hepatitis C Virus Genotype 2 subtype 2c (HCV-2c) is detected as a low prevalence subtype in many countries, except in Southern Europe and Western Africa. The current epidemiology of HCV in Argentina, a low-prevalence country, shows the expected low prevalence for this subtype. However, this subtype is the most prevalent in the central province of Córdoba. Cruz del Eje (CdE), a small rural city of this province, shows a prevalence for HCV infections of 5%, being 90% of the samples classified as HCV-2c. In other locations of Córdoba Province (OLC) with lower prevalence for HCV, HCV-2c was recorded in about 50% of the samples. The phylogenetic analysis of samples from Córdoba Province consistently conformed a monophyletic group with HCV-2c sequences from all the countries where HCV-2c has been sequenced. The phylogeographic analysis showed an overall association between geographical traits and phylogeny, being these associations significant (α = 0.05) for Italy, France, Argentina (places other than Córdoba), Martinique, CdE and OLC. The coalescence analysis for samples from CdE, OLC and France yielded a Time for the Most Common Recent Ancestor of about 140 years, whereas its demographic reconstruction showed a “lag” phase in the viral population until 1880 and then an exponential growth until 1940. These results were also obtained when each geographical area was analyzed separately, suggesting that HCV-2c came into Córdoba province during the migration process, mainly from Europe, which is compatible with the history of Argentina of the early 20th century. This also suggests that the spread of HCV-2c occurred in Europe and South America almost simultaneously, possibly as a result of the advances in medicine technology of the first half of the 20th century

Comparison of Argentinean Saint Louis Encephalitis Virus Non-Epidemic and Epidemic Strain Infections in an Avian Model

St. Louis encephalitis virus (SLEV, Flavivirus, Flaviviridae) is an emerging mosquito-borne pathogen in South America, with human SLEV encephalitis cases reported in Argentina and Brazil. Genotype III strains of SLEV were isolated from Culex quinquefasciatus mosquitoes in Cordoba, Argentina in 2005, during the largest SLEV outbreak ever reported in South America. The present study tested the hypothesis that the recent, epidemic SLEV strain exhibits greater virulence in birds as compared with a non-epidemic genotype III strain isolated from mosquitoes in Santa Fe Province 27 years earlier. The observed differences in infection parameters between adult House sparrows (Passer domesticus) that were needle-inoculated with either the epidemic or historic SLEV strain were not statistically significant. However, only the House sparrows that were infected with the epidemic strain achieved infectious-level viremia titers sufficient to infect Cx. spp. mosquitoes vectors. Furthermore, the vertebrate reservoir competence index values indicated an approximately 3-fold increase in amplification potential of House sparrows infected with the epidemic strain when pre-existing flavivirus-reactive antibodies were present, suggesting the possibility that antibody-dependent enhancement may increase the risk of avian-amplified transmission of SLEV in South America

Mapping environmental susceptibility to Saint Louis encephalitis virus, based on a decision tree model of remotelysensed data

In response to the first human outbreak (January - May 2005) of Saint Louis encephalitis (SLE) virus in Córdoba province, Argentina, we developed an environmental SLE virus risk map for the capital, i.e. Córdoba city. The aim was to provide a map capable of detecting macro-environmental factors associated with the spatial distribution of SLE cases, based on remotely sensed data and a geographical information system. Vegetation, soil brightness, humidity status, distances to water-bodies and areas covered by vegetation were assessed based on pre-outbreak images provided by the Landsat 5TM satellite. A strong inverse relationship between the number of humans infected by SLEV and distance to high-vigor vegetation was noted. A statistical non-hierarchic decision tree model was constructed, based on environmental variables representing the areas surrounding patient residences. From this point of view, 18% of the city could be classified as being at high risk for SLEV infection, while 34% carried a low risk, or none at all. Taking the whole 2005 epidemic into account, 80% of the cases came from areas classified by the model as medium-high or high risk. Almost 46% of the cases were registered in high-risk areas, while there were no cases (0%) in areas affirmed as risk free

West Nile Virus in Argentina: a new emerging infectious agent raising new challenges

El virus West Nile es un flavivirus patógeno para humanos en el Viejo Mundo que ha experimentado recientemente un proceso de emergencia en el continente americano. Desde su introducción en 1999 en EEUU, se ha convertido en un patógeno de preocupación para las poblaciones de aves silvestres al haber provocado allí eventos masivos de mortalidad y porque numerosas especies de aves han experimentado disminuciones significativas de sus poblaciones. Para 2001 el virus ya se había dispersado fuera de EEUU, extendiéndose por América del Sur, América Central y el Caribe. Debido a la falta de un sistema de vigilancia activo para esta patología, no se conoce su verdadero impacto sobre las poblaciones silvestres en esas regiones. Sin embargo, la ausencia de epizootias indica una marcada diferencia en el comportamiento epidemiológico del virus con respecto a EEUU. En Argentina, su ecoepidemiología está poco estudiada y ha recibido poca atención en el ámbito ornitológico. Existen antecedentes de aislamiento viral en equinos enfermos y muertos, casos febriles y de encefalitis en humanos y detección de anticuerpos en aves silvestres en provincias del centro y norte del país. En este trabajo se brinda un análisis actualizado de la situación ecoepidemiológica del virus West Nile, aclarando conceptos básicos de virología y epidemiología para generar un acercamiento e interés de los ornitólogos en el área de los patógenos de importancia para la conservación de las aves. Hace falta una mayor inversión y participación en actividades de investigación interdisciplinarias para aclarar aspectos básicos de la biología, ecología y epidemiología de este nuevo patógeno en el continente americano.The West Nile virus, a human pathogen flavivirus, has recently shown an emerging process through the American continent. Since its introduction in 1999 into the United States, it became a concerned pathogen for wild bird populations, because of massive bird deaths events and significant bird population declines. By 2001 the virus has reached countries in South America, Central America and the Caribbean. The true role of this virus as pathogen for wild birds there is unknown, mainly due to the lack of active surveillance systems. Notwithstanding, there is no epizootic event reported yet, in contrast with the epidemiological behaviour of the virus in the United States. In Argentina, its ecoepidemiology is mostly unknown and it has received little attention from ornithologists. There are reports of viral isolations from dead equines, encephalitis and febrile human cases, as well as neutralizing antibodies detections in wild birds in central and northern provinces. In this review we provide an updated analysis regarding the ecoepidemiology of West Nile virus, and we give basic insights related to basic virological and epidemiological concepts in order to call the attention of ornithologists on the relationship between pathogens and bird conservation. Stronger support on interdisciplinary scientific projects is necessary to provide insight into the biology, ecology and epidemiology of this new viral pathogen in the American continent