Long-Term Study of a Hantavirus Reservoir Population in an Urban Protected Area, Argentina.

Green spaces in urban areas can play a key role in protecting wildlife. However, the presence of wildlife in urban areas can lead to human health risks. Although the presence of the rodent species Oligoryzomys flavescens (hantavirus reservoir) has been recorded in cities of Argentina, its population dynamics in this type of habitat is still unknown. Here, we evaluated: (1) long-term spatial and temporal patterns of O. flavescens abundance and how these patterns were influenced by weather factors and (2) the seroprevalence of hantavirus and the identity of the viral lineage circulating in the population that inhabits the Costanera Sur Ecological Reserve, a protected area in the city of Buenos Aires. Genetic results confirmed that the pathogenic ANDES Central Lechiguanas virus is present in O. flavescens populations inhabiting this urban reserve. Abundance of O. flavescens showed interannual and seasonal fluctuations, with maximum values in winter and spring and minimum ones in summer and autumn. Summers with the highest abundances of O. flavescens were preceded by warmer winters, while winters with lower abundances were preceded by warmer summers. On the other hand, accumulated precipitations in the previous 6 months positively affected winter abundance. These results could help the authorities in charge of the green spaces of Buenos Aires to identify priority areas and times of the year for the implementation of preventive measures that minimize the contact of rodents with visitors. Such measures could be intensified when winters are warmer than normal, and summers are cooler and wetter than normal.

Viral load of patients with hantavirus pulmonary syndrome in Argentina.

Hantavirus causes severe illness including pneumonia, which leads to hospitalization and often death. At present, there is no specific treatment available. The hantavirus pathogenesis is not well understood, but most likely both virus-mediated and host-mediated mechanisms, are involved. The aim of this study was to correlate viral load in samples of hantavirus pulmonary syndrome cases and hantavirus infected individuals, with clinical epidemiological parameters and disease outcome. The variables that could potentially be related with viral load were analyzed. The retrospective study included 73 cases or household contacts, with different clinical evolution. Viral load was measured by reverse-transcription and real time polymerase chain reaction. There was no statistically significant association between blood viral RNA levels and severity of disease. However, viral load was inversely correlated with IgG response in a statistically significant manner. The level of viral RNA was significantly higher in patients infected with Andes virus South lineage, and was markedly low in persons infected with Laguna Negra virus. These results suggest that the infecting viral genotype is associated with disease severity, and that high viral load is associated with a low specific IgG response. Sex, age and disease severity were not related with viral load. Further investigations increasing strikingly the number of cases and also limiting the variables to be studied are necessary.

Daily Movements and Microhabitat Selection of Hantavirus Reservoirs and Other Sigmodontinae Rodent Species that Inhabit a Protected Natural Area of Argentina.

Abundance, distribution, movement patterns, and habitat selection of a reservoir species influence the dispersal of zoonotic pathogens, and hence, the risk for humans. Movements and microhabitat use of rodent species, and their potential role in the transmission of hantavirus were studied in Otamendi Natural Reserve, Buenos Aires, Argentina. Movement estimators and qualitative characteristics of rodent paths were determined by means of a spool and line device method. Sampling was conducted during November and December 2011, and March, April, June, October, and December 2012. Forty-six Oxymycterus rufus, 41 Akodon azarae, 10 Scapteromys aquaticus and 5 Oligoryzomys flavescens were captured. Movement patterns and distances varied according to sex, habitat type, reproductive season, and body size among species. O. flavescens, reservoir of the etiologic agent of hantavirus pulmonary syndrome in the region, moved short distances, had the most linear paths and did not share paths with other species. A. azarae had an intermediate linearity index, its movements were longer in the highland grassland than in the lowland marsh and the salty grassland, and larger individuals traveled longer distances. O. rufus had the most tortuous paths and the males moved more during the non-breeding season. S. aquaticus movements were associated with habitat type with longer distances traveled in the lowland marsh than in the salty grassland. Hantavirus antibodies were detected in 20% of A. azarae and were not detected in any other species. Seropositive individuals were captured during the breeding season and 85% of them were males. A. azarae moved randomly and shared paths with all the other species, which could promote hantavirus spillover events.

Induction of protective immunity in a Syrian hamster model against a cytopathogenic strain of Andes virus.

Andes virus (ANDV) is responsible for the Hantavirus Pulmonary Syndrome cases in Argentina and neighboring countries, with moderate to high case-fatality rates. ANDV has some particular features, which make it unique among other members of the Hantavirus genus such as person-to-person transmission and causing a disease similar to Hantavirus Pulmonary Syndrome in the hamster as an animal model. The kinetics of replication in Vero E6 cells of an ANDV strain isolated in Argentina, called Andes/ARG, was studied. Cytopathic effect and the formation of clear plaques were observed and therefore Andes/ARG could be quantified by classic plaque assay. The Andes/ARG strain was found to be highly lethal in Syrian hamsters allowing experiments to demonstrate the protective potential of vaccines. A recombinant nucleocapsid protein of ANDV induced a long lasting antibody response and protective immunity against a homologous challenge, but to a lower extent against heterologous challenge by the Seoul virus.

Intrathecal antibody production in two cases of yellow fever vaccine associated neurotropic disease in Argentina.

During the period 2007-2008 several epizootics of Yellow fever with dead of monkeys occurred in southeastern Brasil, Paraguay, and northeastern Argentina. In 2008 after a Yellow fever outbreak an exhaustive prevention campaign took place in Argentina using 17D live attenuated Yellow fever vaccine. This vaccine is considered one of the safest live virus vaccines, although serious adverse reactions may occur after vaccination, and vaccine-associated neurotropic disease are reported rarely. The aim of this study was to confirm two serious adverse events associated to Yellow fever vaccine in Argentina, and to describe the analysis performed to assess the origin of specific IgM against Yellow fever virus (YFV) in cerebrospinal fluid (CSF). Both cases coincided with the Yellow fever vaccine-associated neurotropic disease case definition, being clinical diagnosis longitudinal myelitis (case 1) and meningoencephalitis (case 2). Specific YFV antibodies were detected in CSF and serum samples in both cases by IgM antibody-capture ELISA. No other cause of neurological disease was identified. In order to obtain a conclusive diagnosis of central nervous system (CNS) infection the IgM antibody index (AI(IgM) ) was calculated. High AI(IgM) values were found in both cases indicating intrathecal production of antibodies and, therefore, CNS post-vaccinal YFV infection could be definitively associated to YFV vaccination.

Partial genetic characterization of Seoul hantavirus in rats from Buenos Aires City, Argentina, and generation of a Seoul recombinant nucleoprotein antigen

Hemorrhagic fever with renal syndrome (HFRS) is a severe infectious disease characterized by fever, hemorrhage, renal impairment, and thrombocytopenia. At least seven hantaviruses cause HFRS: Hantaan, Seoul (SEOV) (distributed worldwide), Dobrava/Belgrade, Saaremaa, Amur, Thailand and Puumala. To investigate the epidemiology of HFRS and virus transmission in Argentina, we constructed a prokaryotic plasmid encoding the SEOV rNP, of 430 amino acids. After expression, the rNP was tested as an antigen for use in an enzyme-linked immunosorbent assay for infection diagnosis. To determine the current level of virus transmission in wild brown rats or Norway rats (Rattus norvegicus) captured in Buenos Aires City, Argentina, we tested tissues from rats that were determined to be serologically positive for the SEOV, and the viral genome were detected by RT-PCR using specific primers for two fragments of M segment-encoding Gn and Gc proteins. The viral genome was detected in 11 of 21 seropositive rats (52.4 per cent) captured in two parklands. Sequence analysis of a 333-nt region of the Gc-encoding M segment revealed 97 per cent and 96 per cent identity with strains of SEOV from Baltimore and Brazil, respectively. Our genetic data confirm a very low diversity among SEOV virus strains...

A febre hemorrágica com síndrome renal (FHSR) é uma doença grave, caracterizada por febre, hemorragia, falência renal e trombocitopenia. Pelo menos sete hantavírus causam a FHSR: Hantaan, Seoul (SEOV) (de distribuição global), Dobrava-Belgrade, Saaremaa, Amur, Thailand e Puumala. Para investigar a epidemiologia da FHRS e a transmissão viral na Argentina, criamos um plasmídio procariótico que "codifica" a nucleoproteína recombinante do vírus SEOV de 430 aminoácidos. Após a expressão, a nucleoproteína recombinante foi testada como antígeno para uso em ensaio imunoenzimático (ELISA) para diagnóstico da infecção. Para determinar o nível atual de transmissão viral em populações de ratos-marrons ou ratazanas (Rattus norvegicus) capturadas na cidade de Buenos Aires, Argentina, testamos tecidos de ratos selecionados para serem sorologicamente positivos para o vírus SEOV, e o seu genoma viral foi detectado após submetido a RT-PCR utilizando primers específicos para dois fragmentos de proteínas Gn e Gc codificadas pelo segmento M. O genoma viral foi detectado em 11 das 21 ratazanas soropositivas (52,4 por cento), previamente capturadas em dois parques. A análise sequencial de uma região gênica (333 nt) do segmento M "codificador" da proteína Gc apresentou 97 por cento e 96 por cento de similaridade com as cepas de SEOV coletadas em Baltimore e no Brasil, respectivamente. Os dados genéticos levantados confirmam a informação de que há uma diversidade muito pequena entre as cepas do vírus SEOV...

Prevalence of hantavirus infection in wild Rattus norvegicus and R. rattus populations of Buenos Aires City, Argentina.

OBJECTIVE: To determine the prevalence of infection with hantaviruses in wild Rattus norvegicus and R. rattus populations in areas of Buenos Aires city. METHODS: Norway rats and black rats were trapped from 2003 to 2005 at 10 sites throughout Buenos Aires city. Blood samples for serological analysis were collected by cardiac puncture from all individuals captured and tested by enzyme-linked immunosorbent assay for Seoul hantavirus- and Andes virus-specific IgG antibodies. RESULTS: Hantavirus seroprevalence was 11.9% in R. norvegicus (n = 151), varying between 0% and 26.1% depending on the site. Bigger sexually active males were more likely to be infected with Seoul virus than females or juvenile individuals. No antibody-reactive rodents were detected among 33 R. rattus analysed. CONCLUSION: Hantavirus infections are geographically widespread in Buenos Aires city and confirm that they have been enzootic there for at least 20 years.