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1.
Am J Trop Med Hyg ; 35(3): 619-23, 1986 May.
Article in English | MEDLINE | ID: mdl-3706626

ABSTRACT

Laboratory vector competence of Culex (Melanoconion) cedecei was examined for Venezuelan equine encephalomyelitis (VEE) viruses. Colonized adult female mosquitoes originating from a southern Florida population were given bloodmeals from viremic hamsters circulating various titers of 3 hemagglutination inhibition (HI) subtypes of VEE viruses. Following extrinsic incubation of about 3 weeks, mosquitoes were allowed to refeed on uninfected hamsters for transmission trials. Cx. cedecei was highly efficient in becoming infected with and transmitting its sympatric, HI subtype II "Everglades" virus. With bloodmeal titers of 10(0.9) chick embryo cell culture (CEC) plaque forming units (PFU), the infection rate was 9% and transmission occurred following extrinsic incubation. Infection rates were greater than or equal to 80% with oral doses of greater than or equal to 10(1.8), and all infected mosquitoes were capable of transmission following incubation. Cx. cedecei was also highly sensitive to infection with allopatric HI subtype IE Middle American VEE virus isolates. Infection rates were greater than or equal to 50% with bloodmeal titers undetectable by CEC assay. Rates were 100% with oral doses of greater than or equal to 10(0.8) CECPFU. Transmission rates were 100% in all experiments. Similar results were obtained with HI subtype IAB "epizootic" VEE virus isolates from the 1969 Middle American outbreak. Infection rates were 100% with oral doses of greater than or equal to 10(1.2), and transmission rates were 100% after extrinsic incubation. Comparisons with laboratory vector competence of the Middle American enzootic VEE virus vector, Culex (Melanoconion) taeniopus, are discussed.


Subject(s)
Culex/microbiology , Encephalomyelitis, Equine/transmission , Encephalomyelitis, Venezuelan Equine/transmission , Insect Vectors/microbiology , Animals , Cricetinae , Encephalitis Virus, Venezuelan Equine/classification , Encephalitis Virus, Venezuelan Equine/growth & development , Female , Florida , Guatemala , Mesocricetus
2.
Am J Trop Med Hyg ; 33(5): 953-60, 1984 Sep.
Article in English | MEDLINE | ID: mdl-6541436

ABSTRACT

Barriers to dissemination of Middle American epizootic hemagglutination inhibition subtype I-AB, and enzootic, subtype IE, Venezuelan encephalitis (VE) viruses were examined in a colony of the enzootic vector mosquito, Culex (Melanoconion) taeniopus. This species is highly susceptible to oral infection with enzootic, but not epizootic, virus strains. Adult female mosquitoes were intrathoracically inoculated with epizootic virus suspensions to ascertain whether a mesenteron infection barrier exists to these subtype I-AB strains. All inoculated mosquitoes became infected, including those receiving only 10 chick embryo cell culture plaque-forming units (CEC pfu). This confirmed that a mesenteron infection barrier exists to epizootic, but not enzootic Middle American VE strains. Mosquitoes were also given high titer hamster bloodmeals of epizootic viruses and dissected at 2-day intervals to determine the location of virus in the few infected individuals. With mean bloodmeal titers of up to 10(5.3) CEC pfu, only 20% or less of the mosquitoes became infected, and virus replication was confined to the mesenteron. This indicated that a mesenteron escape barrier to epizootic VE viruses exists in this mosquito. Mosquitoes were also given large and small oral doses of enzootic virus strains to compare viral replication patterns. With high titer bloodmeals, virus disseminated from the mesenteron within 4 days of infection, and titers in mosquitoes peaked 7-9 days after infection. All mosquitoes that ingested large doses became infected. Mosquitoes receiving small oral doses of enzootic viruses showed a different pattern of virus replication.(ABSTRACT TRUNCATED AT 250 WORDS)


Subject(s)
Culex/microbiology , Encephalitis Virus, Venezuelan Equine/growth & development , Insect Vectors/microbiology , Animals , Cricetinae , Digestive System/microbiology , Encephalomyelitis, Venezuelan Equine/transmission , Female , Mesocricetus
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