RESUMO
One hundred and fifty-eight strains of Venezuelan equine encephalomyelitis virus were typed antigenically and classified epidemiologically as either epizootic or enzootic. Plaque sizes for 148 of these strains were determined, and the pH requirements for hemagglutination (HA) of goose erythrocytes of 131 were studied. Only antigenic variant group IABC strains could be classified epidemiologically as epizootic. In vitro these strains were characterized by the formation of small plaques in Vero cells and a relatively narrow pH range for optimum HA reactivity. Experimental studies in horses confirmed the fact that only IABC strains have epizootic potential. We concluded that plaque size in Vero cell monolayers would be a useful method of screening VEE viruses for equine virulent strains. Indirect evidence suggested that small plaques resulted from sensitivity to an anionic substance present in the agar overlay medium.
Assuntos
Vírus da Encefalite Equina Venezuelana/patogenicidade , Cavalos/microbiologia , Animais , Antígenos Virais , Vírus da Encefalite Equina Venezuelana/classificação , Vírus da Encefalite Equina Venezuelana/fisiologia , Testes de Hemaglutinação , Concentração de Íons de Hidrogênio , Sorotipagem , Ensaio de Placa Viral , ViremiaAssuntos
Anticorpos Antibacterianos/análise , Febre Q/imunologia , Adolescente , Adulto , Criança , Feminino , Humanos , Masculino , Doenças Profissionais/imunologia , Panamá , RiscoRESUMO
In late June 1973, a small outbreak of equine encephalitis caused by eastern equine encephalomyelitis (EEE) virus occurred in the Republic of Panama. At least 100 horses were affected by the disease and 40 died. More than 1,700 human sera were obtained from areas of virus activity but no serological evidence for infection was found. Four isolates of EEE virus were recovered, one of which was from a small pool of Culex taeniopus mosquitoes. Serologic studies of infected horses and classification by the short incubation hemagglutination-inhibition tests revealed that these isolates were South American strains. Our evidence suggests that another agent virulent for horses was active during this outbreak.
Assuntos
Encefalomielite Equina/epidemiologia , Encefalomielite Equina/veterinária , Doenças dos Cavalos/epidemiologia , Animais , Anticorpos Antivirais/análise , Encéfalo/microbiologia , Vírus da Encefalite Equina do Leste/isolamento & purificação , Encefalomielite Equina/imunologia , Testes de Inibição da Hemaglutinação , Cavalos , Humanos , PanamáRESUMO
The clinical and laboratory findings in ten humans infected with Venezuelan equine encephalitis virus, subtype I-D, are described in this report. Clinical and laboratory data indicate that, in contrast to equine infections, human infection with these enzootic virus strains (I-D) is similar to human infection with epizootic strains (I-ABC). In most cases there was an abrupt onset of fever, muscle pain, and vomiting. Virus was recovered from sera obtained during the first 3 days of illness. Lymphopenia occurred in all patients, and neutropenia occurred in three. No sequelae of these infections were apparent.
Assuntos
Encefalomielite Equina/patologia , Encefalomielite Equina Venezuelana/patologia , Adolescente , Adulto , Encefalomielite Equina Venezuelana/sangue , Enterovirus/isolamento & purificação , Enterovirus/patogenicidade , Feminino , Humanos , Masculino , Pessoa de Meia-IdadeRESUMO
Forty-five horses were infected peripherally or intrathecally with enzootic or epizootic strains of Venezuelan equine encephalomyelitis (VEE) virus. Low titers of virus appeared in cerebrospinal fluid (CSF) after peripheral inoculation of enzootic or epizootic VEE virus strains. Intrathecal infection with either epizootic or enzootic VEE virus produced higher titers of virus in CSF than did peripheral infection. In contrast to peripheral infections with enzootic strains, intrathecal infections with these strains caused death. The animals that died had widespread histopathologic changes and large amounts of virus in brain tissue. The attenuated VEE virus vaccine strain, TC-83, also multiplied in the brain of horses inoculated intrathecally but caused no clinical disease and little histopathologic damage.