RESUMO
Phylogenetic analysis of 20 strains of Venezuelan equine encephalitis (VEE) virus subtype IE isolated from 1961 to 1996 in Mexico and throughout Central America showed that VEE virus subtype IE was monophyletic with respect to other VEE virus subtypes. Nonetheless, there were at least three distinct geographically separated VEE virus IE genotypes: northwestern Panama, Pacific coast (Mexico/Guatemala), and Gulf/Caribbean coast (Mexico/Belize). Strains from the Caribbean coast of Guatemala, Honduras, and Nicaragua may cluster with the Gulf/Caribbean genotype, but additional isolates from the region between Guatemala and Panama will be required to firmly establish their phylogenetic position. Viruses associated with two separate equine epizootics in Mexico in the 1990s were phylogenetically related to nonepizootic viruses from neighboring Guatemala and may represent the emergence or re-emergence of equine-virulent VEE virus subtype IE in Middle America.
Assuntos
Vírus da Encefalite Equina Venezuelana/classificação , Vírus da Encefalite Equina Venezuelana/genética , Encefalomielite Equina Venezuelana/veterinária , Doenças dos Cavalos/virologia , Adulto , Sequência de Aminoácidos , Animais , América Central , Criança , Vírus da Encefalite Equina Venezuelana/isolamento & purificação , Encefalomielite Equina Venezuelana/virologia , Cavalos , Humanos , Recém-Nascido , México , Dados de Sequência Molecular , Filogenia , Precursores de Proteínas/química , Precursores de Proteínas/genética , Proteínas do Envelope Viral/química , Proteínas do Envelope Viral/genéticaRESUMO
Two outbreaks of encephalitis consistent with an etiology of Venezuelan equine encephalitis (VEE) virus occurred in equines on the Pacific coast of southern Mexico in 1993 (Chiapas State) and in 1996 (Oaxaca State). In Chiapas, there were 125 cases, of which 63 were fatal and in Oaxaca, there were 32 cases and 12 fatalities. Virus was isolated from two horses from each outbreak, including three brain isolates and one from blood. Virus isolates (93-42124, ISET-Chi93, Oax131, and Oax142) were shown by indirect immunofluorescence, hemagglutination inhibition, monoclonal antibody ELISA, and nucleotide sequencing to be VEE virus, subtype IE, a type previously thought to be equine-avirulent. Genetic characterization and phylogenetic analysis indicated that the outbreak viruses were identical or nearly identical to one another and that they were closely related to equine-avirulent IE strains from Guatemala and the Gulf coast of Mexico. In a plaque-reduction neutralization test, sera collected from healthy horses in Chiapas and Oaxaca reacted significantly better with isolate 93-42124 than with Guatemala IE isolate 68U201, suggesting that subtle genetic changes may have resulted in alteration of neutralization domains. It is not clear whether these differences may also influence equine virulence. However, renewed VEE virus subtype IE activity in Mexico, and its apparent conversion to equine virulence, underscores the need for increased surveillance, additional laboratory and epidemiologic studies in VEE-endemic regions, and possibly new vaccines.
Assuntos
Surtos de Doenças/veterinária , Vírus da Encefalite Equina Venezuelana/classificação , Encefalomielite Equina Venezuelana/veterinária , Doenças dos Cavalos/virologia , Sequência de Aminoácidos , Animais , Animais Recém-Nascidos , Anticorpos Antivirais/sangue , Antígenos Virais/análise , Vírus da Encefalite Equina Venezuelana/genética , Vírus da Encefalite Equina Venezuelana/imunologia , Encefalomielite Equina Venezuelana/epidemiologia , Encefalomielite Equina Venezuelana/virologia , Ensaio de Imunoadsorção Enzimática/veterinária , Feminino , Doenças dos Cavalos/epidemiologia , Cavalos , Masculino , México/epidemiologia , Camundongos , Dados de Sequência Molecular , Testes de Neutralização/veterinária , Filogenia , Reação em Cadeia da Polimerase/veterinária , Sorotipagem/veterinária , Proteínas do Envelope Viral/química , Proteínas do Envelope Viral/genéticaRESUMO
A survey was conducted from October 1, 1993 to June 30, 1995 to determine the arboviral etiologies of febrile illnesses in the city of Iquitos in the Amazon River Basin of Peru. The study subjects were patients who were enrolled at medical care clinics or in their homes by Peruvian Ministry of Health (MOH) workers as part of the passive and active disease surveillance program of the MOH. The clinical criterion for enrollment was the diagnosis of a suspected viral-associated, acute, undifferentiated febrile illness of < or = 5 days duration. A total of 598 patients were enrolled in the study. Demographic information, medical history, clinical data, and blood samples were obtained from each patient. The more common clinical features were fever, headache, myalgia, arthralgia, retro-ocular pain, and chills. Sera were tested for virus by the newborn mouse and cell culture assays. Viral isolates were identified initially by immunofluorescence using polyclonal antibody. An ELISA using viral-specific monoclonal antibodies and nucleotide sequence analysis were used to determine the specific variety of the viruses. In addition, thin and thick blood smears were observed for malaria parasites. Venezuelan equine encephalitis (VEE) virus subtype I, variety ID virus was isolated from 10 cases, including three cases in October, November, and December 1993, five cases in January and February 1994, and two cases in June 1995. The ELISA for IgM and IgG antibody indicated that VEE virus was the cause of an additional four confirmed and four presumptive cases, including five from January through March 1994 and three in August 1994. Sixteen cases were positive for malaria. The 18 cases of VEE occurred among military recruits (n = 7), agriculture workers (n = 3), students (n = 3), and general laborers (n = 5). These data indicated that an enzootic strain of VEE virus was the cause of at least 3% (18 of 598) of the cases of febrile illnesses studied in the city of Iquitos in the Amazon Basin region of Peru.
Assuntos
Encefalomielite Equina Venezuelana/diagnóstico , Encefalomielite Equina Venezuelana/epidemiologia , Adolescente , Adulto , Idoso , Instituições de Assistência Ambulatorial , Anticorpos Antivirais/análise , Células Cultivadas , Criança , Pré-Escolar , Vírus da Encefalite Equina Venezuelana/classificação , Vírus da Encefalite Equina Venezuelana/genética , Vírus da Encefalite Equina Venezuelana/imunologia , Encefalomielite Equina Venezuelana/sangue , Ensaio de Imunoadsorção Enzimática , Mapeamento de Epitopos , Feminino , Técnica Indireta de Fluorescência para Anticorpo , Humanos , Lactente , Malária/diagnóstico , Masculino , Pessoa de Meia-Idade , Epidemiologia Molecular , Peru/epidemiologia , Filogenia , Reação em Cadeia da Polimerase , Vigilância da População , RNA Viral/análise , RNA Viral/genética , Estudos Soroepidemiológicos , SorotipagemRESUMO
Venezuelan equine encephalitis (VEE) virus was isolated in 1993, 1994, and 1995 from human cases of acute, undifferentiated, febrile illness in the Peruvian Amazon Basin. Two virus isolates were recovered in 1994 from Peruvian soldiers at a jungle outpost near Pantoja in northern Peru, and 10 isolates were obtained from military personnel and civilians in 1993-1995 in Iquitos, an urban center in northeastern Peru. The genetic relationship of these isolates to other VEE virus strains was determined by sequencing 856-867 nucleotide reverse transcription-polymerase chain reaction fragments derived from the PE2 glycoprotein gene. The sequences were compared with those of other VEE virus strains, including representatives of the IAB, IC, ID, IE, II, and IIIC subtypes. The two Pantoja isolates were most closely related to subtype IC and ID viruses previously isolated in Colombia and Venezuela, and to the ID viruses isolated during the 1970s in Iquitos. All of the recent Iquitos isolates were similar to one another, but they were more closely related to Panamanian ID strains than to isolates previously obtained in Iquitos, Peru, or in Colombia and Venezuela. The recent Iquitos VEE viral isolates were the first Panama-genotype VEE ID virus strains identified outside of the Republic of Panama.
Assuntos
Vírus da Encefalite Equina Venezuelana/genética , Encefalomielite Equina Venezuelana/epidemiologia , Glicoproteínas de Membrana/genética , Precursores de Proteínas/genética , RNA Viral/análise , Proteínas Virais , Animais , Células Cultivadas , Chlorocebus aethiops , Colômbia/epidemiologia , Encefalomielite Equina Venezuelana/genética , Humanos , Militares , Epidemiologia Molecular , Panamá/epidemiologia , Peru/epidemiologia , Filogenia , Reação em Cadeia da Polimerase , Alinhamento de Sequência , Análise de Sequência de RNA , Venezuela/epidemiologia , Células VeroRESUMO
Venezuelan equine encephalitis (VEE) epidemics and equine epizootics occurred periodically in the Americas from the 1920s until the early 1970s, when the causative viruses, subtypes IAB and IC, were postulated to have become extinct. Recent outbreaks in Columbia and Venezuela have renewed interest in the source of epidemic/epizootic viruses and their mechanism of interepizootic maintenance. We performed phylogenetic analyses of VEE virus isolates spanning the entire temporal and geographic range of strains available, using 857-nucleotide reverse transcription-PCR products including the E3 and E2 genes. Analyses indicated that epidemic/epizootic viruses are closely related to four distinct, enzootic subtype ID-like lineages. One of these lineages, which occurs in Columbia, Peru, and Venezuela, also included all of the epidemic/epizootic isolates; the remaining three ID-like lineages, which occur in Panama, Peru, Florida, coastal Ecuador, and southwestern Columbia, were apparently not associated with epizootic VEE emergence. Within the Columbia/Peru/Venezuela lineage, three distinct monophyletic groups of epidemic/epizootic viruses were delineated, indicating that VEE emergence has occurred independently at least three times (convergent evolution). Representative, complete E2 amino acid sequences were compared to identify potential determinants of equine virulence and epizootic emergence. Amino acids implicated previously in laboratory mouse attenuation generally did not vary among the natural isolates that we examined, indicating that they probably are not involved in equine virulence changes associated with VEE emergence. Most informative amino acids correlated with phylogenetic relationships rather than phenotypic characteristics, suggesting that VEE emergence has resulted from several distinct combinations of mutations that generate viruses with similar antigenic and equine virulence phenotypes.
Assuntos
Vírus da Encefalite Equina Venezuelana/genética , Encefalomielite Equina Venezuelana/epidemiologia , Encefalomielite Equina Venezuelana/virologia , Sequência de Aminoácidos , Sequência de Bases , Evolução Biológica , DNA Viral , Surtos de Doenças , Vírus da Encefalite Equina Venezuelana/classificação , Genótipo , Dados de Sequência Molecular , Filogenia , Homologia de Sequência de Aminoácidos , Proteínas do Envelope Viral/genéticaRESUMO
An outbreak of a febrile illness characterized by headache, ocular pain, myalgia, and arthralgia occurred during June 1994 among Peruvian army troops in Northern Peru. On June 14-16, 1994, clinical data and blood samples were obtained from eight soldiers with a febrile illness, and from 26 others who had a history of febrile illness during the past three months. A follow-up blood sample was obtained 107 days later from four of the febrile and seven of the afebrile soldiers. Serum samples were tested for dengue (DEN), Oropouche (ORO), and Venezuelan equine encephalitis (VEE) IgM and IgG antibodies by an enzyme-linked immunosorbent assay (ELISA). Virus isolation was performed by inoculation of newborn mice and Vero cell cultures. Viral isolates were identified by immunofluorescence, ELISA, and nucleotide sequencing. A VEE virus infection was confirmed in three of the eight febrile soldiers, two by virus isolation, and one by serology. Antigenic analysis indicated that one of the virus isolates was similar to VEE subtype I, variety ID, viruses previously isolated in Colombia and Venezuela. Nucleotide sequence data showed that both viral isolates were identical to one another and closely related to VEE ID viruses previously isolated in Peru, Colombia, and Venezuela. Serologic results showed that two of 26 afebrile soldiers had IgM antibody to VEE and four had IgG antibody to VEE; two febrile soldiers had IgG antibody in their first serum samples. Oropouche-specific IgM antibody was detected in one of the eight febrile and five of the afebrile soldiers, and 18 of the 34 soldiers had low titers of ORO IgG antibody titers, which did not meet the diagnostic criteria for confirmed cases. All soldiers were negative for DEN IgM antibody, and 10 had flavivirus IgG antibody that reacted with DEN antigens. These data indicated that VEE ID virus was one of the causes of illness among Peruvians soldiers and that this was the first association of this VEE subtype with human disease in Peru.
Assuntos
Infecções por Bunyaviridae/epidemiologia , Surtos de Doenças , Encefalomielite Equina Venezuelana/epidemiologia , Adolescente , Adulto , Animais , Anticorpos Antivirais/sangue , Infecções por Bunyaviridae/virologia , Vírus da Encefalite Equina Venezuelana/imunologia , Vírus da Encefalite Equina Venezuelana/isolamento & purificação , Encefalomielite Equina Venezuelana/virologia , Humanos , Imunoglobulina G/sangue , Imunoglobulina M/sangue , Masculino , Camundongos , Orthobunyavirus , Peru/epidemiologia , Estudos Soroepidemiológicos , Vírus Simbu/imunologia , Vírus Simbu/isolamento & purificaçãoRESUMO
BACKGROUND: Venezuelan equine encephalomyelitis (VEE) virus has caused periodic epidemics among human beings and equines in Latin America from the 1920s to the early 1970s. The first major outbreak since 1973 occurred in Venezuela and Colombia during 1995, and involved an estimated 75,000 to 100,000 people. We report an epidemiological and virological investigation of this epidemic. METHODS: Virus isolates were made in cell culture from human serum, human throat swabs, and brain tissue from aborted and stillborn human fetuses, as well as from horse brain tissue and pooled mosquito collections. Human sera were also tested for VEE-specific antibodies. The serotypes of VEE isolates were identified by antigen assays, and viruses were characterised genetically by sequencing PCR products generated from the E3 and E2 genes. Phylogenetic analyses were done to determine evolutionary relations with respect to previous epidemic/epizootic and enzootic VEE virus isolates. Mosquito collections were made to identify possible vectors, and clinical findings were determined by direct observation of patients visiting hospitals and clinics in affected regions, and by inspecting patient records. Equine vaccination and vector control were used in an attempt to halt the spread of the outbreak. FINDINGS: Most affected people had an acute, self-limited febrile illness of 3 to 4 days duration. However, convulsions were often seen in children, and abortions and fetal deaths occurred in pregnant women infected with VEE virus. Antigenic characterisation of 12 virus isolates spanning the temporal and spatial range of the outbreak indicated that all are VEE serotype IC. Phylogenetic analysis revealed that all of the 1995 viruses were closely related to serotype IC viruses isolated during a large VEE outbreak that occurred in the same regions of Colombia and Venezuela from 1962-1964. A 1983 mosquito isolate from north central Venezuela was also closely related to the 1995 isolates. INTERPRETATION: This outbreak was remarkably similar to one that occurred in same regions of Venezuela and Colombia during 1962-1964. Symptoms of infected patients, estimated mortality rates, meteorological conditions preceding the epidemic, and seasonal patterns of transmission were all very similar to those reported in the previous outbreak. In addition, viruses isolated during 1995 were antigenically and genetically nearly identifical to those obtained during 1962-1964. These findings suggest that the epidemic resulted from the re-emergence of an epizootic serotype IC VEE virus. Identification of a similar virus isolate in mosquitoes in Venezuela in 1983, 10 years after epidemic/epizootic VEE activity ceased, raises the possibility of a serotype IC enzootic transmission cycle in northern Venezuela.
Assuntos
Surtos de Doenças , Encefalomielite Equina Venezuelana/epidemiologia , Adolescente , Adulto , Animais , Criança , Pré-Escolar , Colômbia/epidemiologia , Surtos de Doenças/veterinária , Vírus da Encefalite Equina Venezuelana/classificação , Vírus da Encefalite Equina Venezuelana/isolamento & purificação , Encefalomielite Equina Venezuelana/veterinária , Encefalomielite Equina Venezuelana/virologia , Feminino , Doenças dos Cavalos/epidemiologia , Cavalos , Humanos , Lactente , Pessoa de Meia-Idade , Dados de Sequência Molecular , Gravidez , Venezuela/epidemiologiaRESUMO
The complete nuleotide and predicted amino acid sequences of Venezuelan equine encephalitis (VEE) virus subtype IE (isolate 68U201) were determined and compared to those of other antigenic variants within the VEE complex, strains IAB-TrD, IC-P676, ID-3880, IE-Menall, and II-Fe3-7c. The 68U201 structural proteins were most closely related to their Menall counterparts (97--100% identity) and more distantly related to VEE strains of other antigenic varieties (83--93% identity). With the exception of nsP3, the 68U201 nonstructural proteins were 94--95% identical to those of TrD, P676, and 3880 (nonstructural gene sequences are not available for Menall and Fe3-7c). The amino-terminal region of nsP3 (aa 1--329), which is highly conserved among all alphaviruses, was 93--94% identical for all VEE strains. The nsP3 carboxyl region is highly divergent among alphaviruses in general, but well conserved among previously sequenced VEE strains (>90% identity). Surprisingly, the carboxyl region of 68U201 nsP3 (aa 330--563) was only 59--61% identical to that of subtype IAB, IC, and ID viruses, with large insertions and deletions in addition to numerous substitutions. The differences between the 68U201 and other VEE nsP3 carboxyl regions were not randomly distributed, as there were four domains of high similarity within the nonconserved region. To examine this divergence more closely, we sequenced a portion of the Menall ns3 gene. The 68U201 and Menall nsP3 nonconserved regions were 85.3% identical and had the same basic domain structure, which was distinct from the IAB, IC, and ID nsP3 proteins, suggesting that the domain structure of nsP3 may be subtype/variety-specific. VEE nsP3 sequence diversity may reflect ecological differences such as adaptation to different mosquito vectors or vertebrate hosts.