RESUMO
Following a 19-year hiatus, Venezuelan equine encephalitis (VEE) reemerged in western Venezuela in December 1992. This outbreak is important in understanding VEE emergence because phylogenetic studies imply that sympatric, enzootic, subtype ID VEE viruses mutated to generate the epizootic/epidemic. Although the 1992-1993 strains belong to subtype IC, a serotype implicated in extensive outbreaks during the 1960s and in 1995, relatively small numbers of human and equine cases occurred in 1992-1993. We, therefore, evaluated the pathogenicity of these Venezuelan enzootic ID and epizootic IC viruses to determine 1) if they exhibit phenotypes like those described previously for more distantly related enzootic and epizootic strains, and 2) if the 1992-1993 outbreak was limited by the inability of these IC viruses to exploit equines as amplification hosts. All strains were virulent in mice and guinea pigs, but were benign for cotton rats, natural hosts of enzootic viruses. However, only the IC strains produced equine disease, with mean peak viremias of 10(5) suckling mouse 50% lethal doses per mL serum, and some titers exceeding 10(7). These viremias approximate those observed previously with VEE strains isolated during more extensive epizootics, suggesting that efficient equine amplification did not limit the scope and duration of the 1992-1993 outbreak. Enzootic ID virus infection protected all horses from challenge with epizootic strain P676, supporting the hypothesis that epizootics bypass regions of enzootic transmission due to natural immunization of equines by enzootic VEE viruses.
Assuntos
Surtos de Doenças/veterinária , Vírus da Encefalite Equina Venezuelana/patogenicidade , Encefalomielite Equina Venezuelana/epidemiologia , Encefalomielite Equina Venezuelana/virologia , Doenças dos Cavalos/virologia , Viremia/virologia , Animais , Anopheles , Chlorocebus aethiops , Cricetinae , Vírus da Encefalite Equina Venezuelana/classificação , Encefalomielite Equina Venezuelana/sangue , Feminino , Cobaias , Doenças dos Cavalos/sangue , Doenças dos Cavalos/epidemiologia , Cavalos , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C3H , Camundongos Endogâmicos C57BL , Distribuição Aleatória , Ratos , Doenças dos Roedores/virologia , Sigmodontinae , Venezuela/epidemiologia , Células Vero , VirulênciaRESUMO
This report describes Trocara virus, a newly recognized member of the genus Alphavirus, that has been isolated from Aedes serratus mosquitoes collected at two widely separated sites in the Amazon Basin. Biological, antigenic and genetic characteristics of the new virus are given. Results of these studies indicate that Trocara virus is the first member of a newly discovered antigenic complex within the family Togaviridae genus Alphavirus. The public health and veterinary importance of Trocara virus is still unknown.
Assuntos
Aedes/virologia , Alphavirus/genética , Alphavirus/isolamento & purificação , Alphavirus/ultraestrutura , Animais , Brasil , Testes de Fixação de Complemento , Cricetinae , Primers do DNA , Testes de Hemaglutinação , Camundongos , Microscopia Eletrônica , Peru , Reação em Cadeia da Polimerase , RNA Viral/isolamento & purificação , Reação em Cadeia da Polimerase Via Transcriptase ReversaRESUMO
The nucleotide sequence of the S RNA segment of the Oropouche (ORO) virus prototype strain TRVL 9760 was determined and found to be 754 nucleotides in length. In the virion-complementary orientation, the RNA contained two overlapping open reading frames of 693 and 273 nucleotides that were predicted to encode proteins of 231 and 91 amino acids, respectively. Subsequently, the nucleotide sequences of the nucleocapsid genes of 27 additional ORO virus strains, representing a 42 year interval and a wide geographical range in South America, were determined. Phylogenetic analyses revealed that all the ORO virus strains formed a monophyletic group that comprised three distinct lineages. Lineage I contained the prototype strain from Trinidad and most of the Brazilian strains, lineage II contained six Peruvian strains isolated between 1992 and 1998, and two strains from western Brazil isolated in 1991, while lineage III comprised four strains isolated in Panama during 1989.
Assuntos
Genes Virais , Nucleocapsídeo/genética , Vírus Simbu/genética , Animais , Sequência de Bases , Primers do DNA/genética , Humanos , Dados de Sequência Molecular , Fases de Leitura Aberta , Orthobunyavirus/classificação , Orthobunyavirus/genética , Filogenia , RNA Viral/genética , Vírus Simbu/classificação , Vírus Simbu/isolamento & purificação , América do SulRESUMO
Eastern equine encephalitis virus (EEEV), the sole species in the EEE antigenic complex, is divided into North and South American antigenic varieties based on hemagglutination inhibition tests. Here we describe serologic and phylogenetic analyses of representatives of these varieties, spanning the entire temporal and geographic range available. Nucleotide sequencing and phylogenetic analyses revealed additional genetic diversity within the South American variety; 3 major South/Central American lineages were identified including one represented by a single isolate from eastern Brazil, and 2 lineages with more widespread distributions in Central and South America. All North American isolates comprised a single, highly conserved lineage with strains grouped by the time of isolation and to some extent by location. An EEEV strain isolated during a 1996 equine outbreak in Tamaulipas State, Mexico was closely related to recent Texas isolates, suggesting southward EEEV transportation beyond the presumed enzootic range. Plaque reduction neutralization tests with representatives from the 4 major lineages indicated that each represents a distinct antigenic subtype. A taxonomic revision of the EEE complex is proposed.
Assuntos
Variação Antigênica/genética , Vírus da Encefalite Equina do Leste/genética , Encefalomielite Equina/epidemiologia , Variação Genética , Filogenia , Sequência de Aminoácidos , Animais , Sequência de Bases , Aves , América Central/epidemiologia , Primers do DNA/química , DNA Viral/química , Surtos de Doenças/veterinária , Vírus da Encefalite Equina do Leste/imunologia , Cavalos , Humanos , Testes de Neutralização/veterinária , América do Norte/epidemiologia , RNA Viral/isolamento & purificação , Reação em Cadeia da Polimerase Via Transcriptase Reversa/veterinária , Alinhamento de Sequência , Análise de Sequência de RNA , Sigmodontinae/virologia , América do Sul/epidemiologiaRESUMO
This paper reports the first isolation of Mayaro (MAY) virus from a patient infected in French Guiana. The identification was initially performed using immunofluorescent antibody testing with specific mouse antibody, and confirmed by plaque-reduction neutralization testing and reverse transcription-polymerase chain reaction. To determine if MAY virus infection is widespread in French Guiana, a serosurvey was performed to determine the prevalence of antibody to this virus in various ethnic groups and areas of French Guiana. Human sera (n = 1,962) were screened using the hemagglutination inhibition (HI) test. To determine whether MAY virus circulates in the rain forest, a serosurvey in monkey populations was performed. Monkey sera (n = 150) were also screened for antibody to MAY virus using HI testing. Of the human sera tested, 6.3% were positive for anti-MAY virus antibodies. Significant differences in MAY virus seroprevalence between different age groups were observed. Seroprevalence rates increased with age, with a large increase in people 10-19 years of age in comparison with those less than 10 years of age. After adjustment for age, significant differences were also found between places of residence. The prevalence of anti-MAY virus antibody was higher in people living in contact with the forest, especially in the Haut Oyapock area (odds ratio [OR] = 97.7, 95% confidence interval [CI] = 48.2-197.9) and along the Maroni River (OR = 39.7, 95% CI = 20.6-76.6). The ethnic differences observed in this study were probably due to differences in residence. Among monkeys, higher seroprevalence rates were found in Alouatta seniculus (66.0%) than in Saguinus midas (18.2%). Among Alouatta, the seroprevalence increased significantly with weight (and therefore with age). This study indicates that MAY virus is present in French Guiana, and human infections occur in areas where people live near the tropical rain forest.
Assuntos
Infecções por Alphavirus/epidemiologia , Alphavirus/isolamento & purificação , Anticorpos Antivirais/sangue , Doenças dos Macacos/epidemiologia , Adolescente , Adulto , Distribuição por Idade , Idoso , Idoso de 80 Anos ou mais , Alouatta , Alphavirus/genética , Alphavirus/imunologia , Animais , Criança , Pré-Escolar , Feminino , Imunofluorescência , Guiana Francesa/epidemiologia , Testes de Inibição da Hemaglutinação , Humanos , Lactente , Masculino , Pessoa de Meia-Idade , Testes de Neutralização , Reação em Cadeia da Polimerase , Prevalência , SaguinusRESUMO
This paper characterizes Guanarito virus, the etiologic agent of Venezuelan hemorrhagic fever. Based on its morphology and antigenic properties, Guanarito virus appears to be a new member of the Tacaribe complex of the genus Arenavirus, family Arenaviridae. Complement fixation and indirect fluorescent antibody tests showed that Guanarito virus and its antiserum are broadly cross-reactive with other members of the Tacaribe complex, but it can be differentiated from other members of the complex by neutralization test. Guanarito virus causes mortality in suckling mice and adult guinea pigs, but not in adult mice. Inoculated rhesus monkeys developed viremia and became ill; however, they subsequently recovered and responded with production of antibody. To date, all isolates of Guanarito virus have come from sick persons or wild rodents living within a single geographic focus in the central plains of Venezuela.
Assuntos
Arenavirus do Novo Mundo/patogenicidade , Febre Hemorrágica Americana/microbiologia , Adulto , Animais , Animais Lactentes , Antígenos Virais/análise , Antígenos Virais/imunologia , Arenavirus do Novo Mundo/imunologia , Arenavirus do Novo Mundo/ultraestrutura , Linhagem Celular , Testes de Fixação de Complemento , Reações Cruzadas , Efeito Citopatogênico Viral , Imunofluorescência , Cobaias , Humanos , Macaca mulatta , Masculino , Camundongos , Microscopia Eletrônica , Testes de Neutralização , Venezuela , Células Vero , Viremia/microbiologiaRESUMO
An outbreak of severe haemorrhagic illness began in the municipality of Guanarito, Portuguesa State, Venezuela, in September, 1989. Subsequent detailed study of 15 cases confirmed the presence of a new viral disease, designated Venezuelan haemorrhagic fever. Characteristic features are fever, toxicity, headache, arthralgia, diarrhoea, conjunctivitis, pharyngitis, leucopenia, thrombocytopenia, and haemorrhagic manifestations. Other features include facial oedema, cervical lymphadenopathy, nausea/vomiting, cough, chest or abdominal pain, and convulsions. The patients ranged in age from 6 to 54 years; all were residents of rural areas in central Venezuela, and 9 died. Infection with Guanarito virus, a newly recognised arenavirus, was shown by direct culture or by serological confirmation in all cases. Epidemiological studies suggest that the disease is endemic in some rural areas of central Venezuela and that it is rodent-borne. Venezuelan haemorrhagic fever has many similarities to Lassa fever and to the arenavirus haemorrhagic fevers that occur in Argentina and Bolivia.
Assuntos
Surtos de Doenças , Febre Hemorrágica Americana/epidemiologia , Doença Aguda , Adolescente , Adulto , Animais , Animais Selvagens/microbiologia , Arenavirus do Novo Mundo/isolamento & purificação , Criança , Feminino , Febre Hemorrágica Americana/complicações , Febre Hemorrágica Americana/transmissão , Humanos , Masculino , Pessoa de Meia-Idade , Roedores/microbiologia , Saúde da População Rural , Venezuela/epidemiologiaRESUMO
Three geographical strains of Aedes aegypti from Thailand (Amphur), East Africa (Kampala), and the West Indies (Santo Domingo) were compared for susceptibility to infection with low-passage yellow fever virus (French viscerotropic) as well as for ability to transmit virus by bite at varying extrinsic incubation periods. Santo Domingo strain appeared the most competent and Kampala the least when mosquitoes were exposed to a low level virus-infecting blood meal; at higher virus levels, a similar trend was noted but differences were less evident and in no case were the differences statistically significant. All three strains were infected with and transmitted yellow fever virus.
Assuntos
Aedes/microbiologia , Insetos Vetores , Vírus da Febre Amarela , África Oriental , Animais , Especificidade da Espécie , Tailândia , Índias Ocidentais , Vírus da Febre Amarela/crescimento & desenvolvimentoRESUMO
Pacui virus, originally obtained from forest rodents, was isolated 100 times from 61,437 specimens (658 pools) of the phlebotomine fly Lutzomyia flaviscutellata, collected from rodent-baited traps in the forests of Belem, Para, Brazil in the period October 1968 through September 1970. Isolations were made from engorged and unengorged females and from males (3 strains), and occurred in all 24 months. Pacui virus also was isolated from the blood of two wild rodents (Oryzomys), but not from 424 L. infraspinosa, 12,000 mosquitoes, or sentinel mice. Pacui virus neutralizing antibodies were detected in serum of six bait animals after exposure to biting flies in the forest, in 30% of wild rodents surveyed (including two from Amapa Territory), and in 10% of marsupials, but were absent in human survey sera and in bats. Low-passage Pacui virus produced viremia in and was lethal to infant mice by the subcutaneous route. L. flaviscutellata was most abundant in the dry season, in which period Pacui virus isolations increased. This fly is strongly attracted to rodents close to the ground. L. flaviscutellata also yielded single strains of Guama, Icoaraci, and BeAr 177325 viruses.