RESUMEN
This article describes clinical, etiologic and pathologic diagnosis of an outbreak of equine leukoencephalomalacia. Two samples of the corn consumed by the affected horses contained fumonisin B1 at levels of 46 and 53 ug/g and Fusarium moniliforme, a good in vitro mycotoxin producer.
Asunto(s)
Animales , Zea mays/microbiología , Encefalomielitis Equina/microbiología , Fusarium/aislamiento & purificación , Enfermedades de los Caballos/microbiología , Ingestión de Alimentos , Muestras de Alimentos , Encefalomielitis Equina/patología , Encefalomielitis Equina/veterinaria , Caballos , Enfermedades de los Caballos/patologíaRESUMEN
Evolution of viruses in the eastern equine encephalomyelitis (EEE) complex was studied by analyzing RNA sequences and oligonucleotide fingerprints from isolates representing the North and South American antigenic varieties. By using homologous sequences of Venezuelan equine encephalomyelitis virus as an outgroup, phylogenetic trees revealed three main EEE virus monophyletic groups. A North American variety group included all isolates from North America and the Caribbean. One South American variety group included isolates from the Amazon basin in Brazil and Peru, while the other included strains from Argentina, Guyana, Ecuador, Panama, Trinidad, and Venezuela. No evidence of heterologous recombination was obtained when three separate regions of the EEE virus genome were analyzed independently. Estimates of the overall rate of EEE virus evolution (nucleotide substitution) were 1.6 x 10(-4) substitution per nucleotide per year for the North American group and 4.3 x 10(-4) for the Argentina-Panama South American group. Evolutionary rate estimates for the North American group increased over 10-fold (from about 2 x 10(-5) to 4 x 10(-4)) concurrent with divergence of two monophyletic groups during the early 1970s. The North and South American antigenic varieties diverged roughly 1,000 years ago, while the two main South American groups diverged about 450 years ago. Analysis of multiple strains isolated from an upstate New York transmission focus during the same years suggested that, in certain locations, EEE virus may be relatively isolated for short time periods.
Asunto(s)
Virus de la Encefalitis Equina del Este/clasificación , Virus de la Encefalitis Equina del Este/genética , ARN Viral/genética , Antígenos Virales/genética , Secuencia de Bases , Evolución Biológica , Región del Caribe , América Central , Encefalomielitis Equina/microbiología , Variación Genética , Datos de Secuencia Molecular , Mutagénesis , América del Norte , Homología de Secuencia de Ácido Nucleico , América del Sur , Factores de TiempoRESUMEN
Comparative studies are described on the virulence of the western equine encephalomyelitis (WEE) complex viruses for mice. Three epizootic WEE virus strains (McMillan, Cba 87, and Cba CIV 180) and five enzootic WEE complex viruses (Highlands J [HJ], Y62-33, Aura, Fort Morgan [FM], and WEE AG80-646) were examined. The neurovirulence and the neuroinvasiveness of these viruses for adult mice were established and correlated with viremia and virus replication in brain tissue. Adult mice inoculated intraperitoneally showed differential responses that corresponded to the epidemiologic attributes of WEE viruses. Viruses associated with equine epizootics were neurovirulent and neuroinvasive, whereas enzootic viruses were neither neuroinvasive nor neurovirulent. In North America, HJ virus appears to be an antigenic link with an intermediate virulence between epizootic WEE virus and the enzootic FM virus. The HJ virus has been associated with rare cases of sporadic equine and human diseases. In South America, no virus with intermediate virulence characteristics has been described. We speculate that epizootics may arise from nonpathogenic strains such as AG80-646 maintained in enzootic transmission cycles.
Asunto(s)
Virus de la Encefalitis Equina del Oeste/patogenicidad , Encefalomielitis Equina/microbiología , Animales , Animales Lactantes , Encéfalo/microbiología , Culicidae/microbiología , Brotes de Enfermedades , Virus de la Encefalitis Equina del Oeste/fisiología , Encefalomielitis Equina/epidemiología , Humanos , Ratones , América del Norte/epidemiología , América del Sur/epidemiología , Viremia/microbiología , Virulencia , Replicación ViralRESUMEN
Neutralizing antibodies to EEE (6.7%), WEE (1.2%), ILH (26.6%), MAG (28.2%) and TCM (15.7%) viruses were found in sera of 432 equines of the Brazilian Pantanal, area where undiagnosed horse deaths are frequently observed. A 4-fold rise in CF titer to EEE virus was detected in acute and convalescent sera of an encephalitis horse sacrificed in 1992. Antibodies to EEE, ILH, MAG and TCM viruses were detected in horses less than 2 years old indicating recent circulation of these viruses in the Pantanal. The evidence of recent equine encephalitis associated with rising CF titer to EEE warrants a more intensive study with attempts to isolate virus from horses with clinical manifestations of encephalitis.
Asunto(s)
Encefalomielitis Equina/veterinaria , Enfermedades de los Caballos/epidemiología , Animales , Anticuerpos Antivirales , Brasil/epidemiología , Encefalomielitis Equina/epidemiología , Encefalomielitis Equina/inmunología , Encefalomielitis Equina/microbiología , Enfermedades de los Caballos/inmunología , Enfermedades de los Caballos/microbiología , Caballos/microbiologíaRESUMEN
An overview of ecological, epidemiological and clinical findings of potential arthropod-borne encephalitis viruses circulating in the Amazon Region of Brazil are discussed. These viruses are the Eastern Equine Encephalitis (EEE), Western Equine Encephalitis (WEE), St. Louis Encephalitis (SLE), Mucambo (MUC) and Pixuna (PIX). These last two are subtypes (III and IV) of Venezuelan Equine Encephalitis virus. The areas of study were the highways and projects of development, as well as places where outbreaks of human diseases caused by arboviruses had been detected. These viruses are widespread in all Amazonia, and at least four of them, EEE, WEE, SLE and MUC are pathogenic to man. EEE and WEE infections were detected by serology, while SLE and MUC by either serology and virus isolation. The PIX virus has the lowest prevalence and, it was isolated in only a few cases, one being from a laboratory infection. Wild birds are the main hosts for all these viruses, except MUC, whose major hosts are rodents. The symptoms presented by infected people were generally a mild febrile illness. Although, jaundice was observed in two individuals from whom SLE was isolated. A comparison of the clinical symptoms presented by the patients in the Amazon Region and other areas of America, especially in the USA is made. In Brazilian Amazon region epidemics have not been detected although, at least, one EEE epizootic was recorded in Bragança, Para State, in 1960. At that time, of 500 horses that were examined 61% were positive to EEE by HI and of them 8.2% died. On the other hand, SLE has caused four epizootics in a forest near Belem. Wild birds and sentinel monkeys were infected, but no human cases were reported.
Asunto(s)
Virus de la Encefalitis , Encefalitis por Arbovirus/epidemiología , Encefalomielitis Equina/epidemiología , Animales , Aves/microbiología , Brasil/epidemiología , Encefalitis por Arbovirus/microbiología , Encefalomielitis Equina/microbiología , Humanos , Insectos Vectores/microbiología , RatonesRESUMEN
In 1983, 17 virus strains were isolated from mosquitoes collected during an outbreak of western equine encephalitis in Santa Fe Province, Argentina. Strains of western equine encephalitis, Venezuelan equine encephalitis, St. Louis encephalitis, and Antequera viruses were isolated, as were several bunyaviruses of the California and Bunyamwera serogroups and a new vesiculovirus. Complement fixation and neutralization tests were used to identify the California serogroup virus as a subtype of Melao virus, the Bunyamwera serogroup virus as a subtype of both Maguari and Playas viruses, and the vesiculovirus as a newly recognized agent for which the name Calchaqui virus is proposed. A limited serosurvey of horses and humans in Santa Fe Province and horses from the adjacent Santiago del Estero Province was performed to determine the prevalence of neutralizing antibody to the subtypes of Melao and Maguari viruses and to Calchaqui virus. The high prevalence of antibodies to these three agents indicates the need for further studies of their disease potential in horses, because they are closely related to several other viruses that are known equine pathogens.
Asunto(s)
Virus Bunyamwera/aislamiento & purificación , Bunyaviridae/aislamiento & purificación , Virus de la Encefalitis de California/aislamiento & purificación , Encefalomielitis Equina/microbiología , Enfermedades de los Caballos/microbiología , Virus de la Estomatitis Vesicular Indiana/aislamiento & purificación , Animales , Argentina , Pruebas de Fijación del Complemento , Culex/microbiología , Culicidae/microbiología , Encefalomielitis Equina/veterinaria , Femenino , Técnica del Anticuerpo Fluorescente , Caballos/microbiología , Humanos , Pruebas de Neutralización , Células Vero/microbiología , Ensayo de Placa ViralRESUMEN
This is the introductory paper to a series on the ecology of arboviruses in Argentina. Epizootics of equine encephalitis have occurred since at least 1908, principally in the Pampa and Espinal biogeographic zones, with significant economic losses; human cases of encephalitis have been rare or absent. Both western equine and eastern equine encephalitis viruses have been isolated from horses during these epizootics, but the mosquitoes responsible for transmission have not been identified. A number of isolations of Venezuelan equine encephalitis (VEE) virus were reported between 1936 and 1958 in Argentina, but the validity of these findings has been seriously questioned. Nevertheless, serological evidence exists for human infections with a member of the VEE virus complex. Serological surveys conducted in the 1960s indicate a high prevalence of infection of humans and domestic animals with St. Louis encephalitis (SLE), and 2 SLE virus strains have been isolated from rodents. Human disease, however, has rarely been associated with SLE infection. Only 7 isolations of other arboviruses have been described (3 of Maguari, 1 of Aura, 2 of Una, and 1 of an untyped Bunyamwera group virus). In 1977, we began longitudinal field studies in Santa Fe Province, the epicenter of previous equine epizootics, and in 1980 we extended these studies to Chaco and Corrientes provinces. The study sites are described in this paper.
Asunto(s)
Infecciones por Arbovirus/epidemiología , Animales , Infecciones por Arbovirus/microbiología , Arbovirus , Argentina , Aves , Bovinos , Niño , Clima , Ecología , Virus de la Encefalitis de San Luis , Virus de la Encefalitis Equina Venezolana , Virus de la Encefalitis Equina del Oeste , Encefalitis de San Luis/epidemiología , Encefalitis de San Luis/microbiología , Encefalomielitis Equina/epidemiología , Encefalomielitis Equina/microbiología , Encefalomielitis Equina/veterinaria , Encefalomielitis Equina Venezolana/epidemiología , Encefalomielitis Equina Venezolana/microbiología , Encefalomielitis Equina Venezolana/veterinaria , Geografía , Enfermedades de los Caballos/epidemiología , Enfermedades de los Caballos/microbiología , Caballos/microbiología , HumanosAsunto(s)
Humanos , Animales , Cuba , Reservorios de Enfermedades , Ecología , Especificidad de la Especie , Animales/microbiología , Animales Salvajes/microbiología , Anticuerpos Antivirales/análisis , Arbovirus/aislamiento & purificación , Arbovirus/inmunología , Aves/microbiología , /aislamiento & purificación , Encefalomielitis Equina/microbiología , Encefalomielitis Equina/transmisión , Mamíferos/microbiología , Reptiles/microbiologíaAsunto(s)
Grupos de Población Animal/microbiología , Animales Salvajes/microbiología , Arbovirus/aislamiento & purificación , Animales , Anticuerpos Antivirales/análisis , Arbovirus/inmunología , Aves/microbiología , Cuba , Reservorios de Enfermedades , Ecología , Virus de la Encefalitis Equina del Este/aislamiento & purificación , Encefalomielitis Equina/microbiología , Encefalomielitis Equina/transmisión , Humanos , Mamíferos/microbiología , Reptiles/microbiología , Especificidad de la EspecieRESUMEN
Comparative data with regard to the properties of Venezuelan equine encephalomyelitis (VEE) virus isolated from HeLa carrier cultures by transfection in different cell cultures have been obtained. Introduction of DNA extracted from the carrier cultures into BHK-21 cell cultures resulted in production of an actively multiplying medium-plaque virus, and parallel addition of the same DNA preparations in chick fibroblast or monkey kidney cultures led to production of small-plaque virus with a low reproduction potential. The virus produced by transfection of BHK-21 cells differed from that produced in chick fibroblast and monkey kidney cultures in electrophoretic mobility of virion envelope proteins. The infection of these cultures with virions as well as infection with genome RNA did not result in production of differing virus variants. The importance of the experimental genetic data for the problem of the nature of the infectious principle of cellular DNA preparations and of the form of existence of viral genome in chronically infected cultures with infection of the integrative type is discussed.
Asunto(s)
Virus de la Encefalitis Equina Venezolana/genética , Encefalomielitis Equina/microbiología , Variación Genética , Transfección , Animales , Embrión de Pollo , Enfermedad Crónica , Virus de la Encefalitis Equina Venezolana/aislamiento & purificación , Fibroblastos/microbiología , Haplorrinos , Células HeLa/microbiología , Humanos , Riñón , Ensayo de Placa Viral , Cultivo de VirusAsunto(s)
Adyuvantes Inmunológicos/inmunología , Benzofuranos/inmunología , Encefalomielitis Equina/microbiología , Encefalomielitis Equina Venezolana/microbiología , Fluorenos/inmunología , Tilorona/inmunología , Vacunas Atenuadas/inmunología , Animales , Anticuerpos Antivirales/análisis , Formación de Anticuerpos , Femenino , Formaldehído , Macaca mulatta , Masculino , RatonesRESUMEN
Virion polypeptide compositions of 26 isolates of Venezuelan encephalitis virus were analyzed by a reproducible and comparative technique of discontinuous sodium dodecyl sulfate-polyacrylamide slab gel electrophoresis. Although the molecular weight of the core polypeptide for each isolate was 36,000, numbers and molecular weights of envelope glycoproteins were heterogeneous. Isolates associated with human, but not equine, disease usually had two glycoproteins of 50,000 to 51,000 and 51,000 to 55,000 molecular weight, whereas isolates associated with both human and equine disease usually had an additional, third polypeptide band of either 45,000 to 46,000 or 56,000 to 58,000 molecular weight. The former isolates were in hemagglutination inhibition subtypes I-D, I-E, III, or IV, and the latter were in subtypes I-A, I-B, I-C, or II. Thus virion envelope glycoproteins should be useful markers of Venezuelan encephalitis virus isolates in epidemiological investigations.
Asunto(s)
Virus de la Encefalitis Equina Venezolana/análisis , Encefalomielitis Equina/microbiología , Encefalomielitis Equina Venezolana/microbiología , Glicoproteínas/análisis , Enfermedades de los Caballos/microbiología , Proteínas Virales/análisis , Animales , Antígenos Virales , Virus de la Encefalitis Equina Venezolana/inmunología , Encefalomielitis Equina Venezolana/veterinaria , Pruebas de Inhibición de Hemaglutinación , Caballos , Humanos , Peso MolecularRESUMEN
Mice of different ages were infected i.p. or i.c. by 23 different strains of VEE virus. The course of the virus host interaction was specified in terms of the efficiency of infection, the outcome of infection as lethality or protection and the survival time. These separately quantifiable features all showed several host-maturation events that combine to provide a multifactorial specification of virus-strains and host-responses. This base-line for correlations with the responses of principal hosts (equidae and man) may be expanded to test correlations with the antigenic or in vitro characteristics of virus-strains.
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Virus de la Encefalitis Equina Venezolana/patogenicidad , Encefalomielitis Equina/microbiología , Encefalomielitis Equina Venezolana/microbiología , Envejecimiento , Animales , Encefalomielitis Equina Venezolana/inmunología , Inmunidad , Dosificación Letal Mediana , Masculino , RatonesRESUMEN
This study reports the induction in vivo of aneuploidy in bone marrow cells of the Syrian hamster after short-term infection with Venezuelan encephalitis virus.
Asunto(s)
Aneuploidia , Aberraciones Cromosómicas/microbiología , Virus de la Encefalitis Equina Venezolana/fisiología , Encefalomielitis Equina/microbiología , Encefalomielitis Equina Venezolana/microbiología , Animales , Médula Ósea/microbiología , Células Cultivadas , Trastornos de los Cromosomas , Cricetinae , Encefalomielitis Equina Venezolana/genéticaAsunto(s)
Virus de la Encefalitis Equina Venezolana/patogenicidad , Encefalomielitis Equina/microbiología , Encefalomielitis Equina Venezolana/microbiología , Animales , Encéfalo/microbiología , Modelos Animales de Enfermedad , Virus de la Encefalitis Equina Venezolana/crecimiento & desarrollo , Encefalomielitis Equina Venezolana/mortalidad , Inmunización Pasiva , Masculino , Ratas , Replicación ViralRESUMEN
Eighty-three wild mammals of ten species were inoculated with a first mouse passage level Venezuelan encephalitis (VE) virus isolated from south Texas in 1971 during the VE outbreak. Rodents were highly susceptible to VE infection and circulated VE virus at levels ranging from 10(7.7) to 10(11.5) suckling mouse intracranial lethal doses per ml for 2 to 4 days. These levels of virus could easily infect vector mosquitoes. Mortality was high in all species of rodents except Sigmodon hispidus, adult Neotoma micropus, and adult Peromyscus leucopus. Lagomorphs were susceptible to VE infection but circulated VE virus at or near mosquito threshold levels for 1 day only. Raccoons and opossums were relatively resistant to VE infection or circulated low levels of virus in the blood. Juvenile animals of four species were more susceptible and experienced higher viremias than did adults. In two of the four, mortality was higher in the juveniles than in adults. A consideration of results obtained during this study and those of other investigators led to the conclusion that equines were of major importance, that canines, lagomorphs and rodents were of minor importance, and that other species tested were of no importance as virus amplifiers in VE epizootics.