RESUMO
The natural transmission of dengue virus from an infected female mosquito to its progeny, namely the vertical transmission, was researched in wild caught Aedes aegypti during an important outbreak in the town of Santa Cruz de la Sierra, Bolivia. Mosquitoes were collected at the preimaginal stages (eggs, larvae and pupae) then reared up to adult stage for viral detection using molecular methods. Dengue virus serotypes 1 and 3 were found to be co-circulating with significant higher prevalence in male than in female mosquitoes. Of the 97 pools of Ae. aegypti (n = 635 male and 748 female specimens) screened, 14 pools, collected in February-May in 2007, were found positive for dengue virus infection: five DEN-1 and nine DEN-3. The average true infection rate (TIR) and minimum infection rate (MIR) were respectively 1.08% and 1.01%. These observations suggest that vertical transmission of dengue virus may be detected in vectors at the peak of an outbreak as well as several months before an epidemic occurs in human population.
Assuntos
Aedes/virologia , Vírus da Dengue/fisiologia , Dengue/transmissão , Insetos Vetores/virologia , Animais , Bolívia/epidemiologia , Dengue/epidemiologia , Surtos de Doenças , Feminino , Masculino , Fatores SexuaisRESUMO
The conditions of maintenance of YF virus in brazilian Amazonia are not yet elucidated. Generally, the presence of the virus is attested by human cases of sylvatic origin. During a survey done at the exact place where a man have probably been contaminated, it was possible for the first time in South America, to estimate the mean parity rate of a population of the potential vector Haemagogus janthinomys, from which the YF virus was actually isolated. The survival rate (Ts = 0.96), the biting rate (0.60 mosquitoes/man x hour), and the infection rate (1.71%) were also determinated for the same mosquitoes and have values compatible with the probable conditions of the human contamination. However, more data are needed, in particular in relation with other possible human contaminations and/or circulation of the YF virus in the monkey population (extension and duration of the epizootic episode), in order to know what maintenance cycle is prevalent in this region: a low level transmission, with the mosquito being a "vector-reservoir", or a "constantly moving epizootic wave".
Assuntos
Culicidae , Entomologia , Insetos Vetores , Febre Amarela/epidemiologia , Vírus da Febre Amarela/isolamento & purificação , Adolescente , Animais , Brasil/epidemiologia , Culicidae/classificação , Culicidae/crescimento & desenvolvimento , Culicidae/microbiologia , Coleta de Dados , Reservatórios de Doenças , Água Doce , Haplorrinos/microbiologia , Humanos , Masculino , Árvores , Febre Amarela/microbiologia , Febre Amarela/transmissãoRESUMO
The bioecological parameters which are of special importance in the epidemiology of Dengue, Yellow Fever, and other arboviruses are discussed. Three levels are retained: the nature of Aedes aegypti-man contacts, the susceptibility of the mosquito to the pathogen and multiplication of the latter, and the transmission. The trophic preferences, the density variations, the daily survival rate, the egg diapause, and man influences are the main vector-dependent ecological factors. Temperature and genetical nature of viral and mosquito strains are particularly important in susceptibility and multiplication studies. Efficacy of the oral transmission is also temperature-dependent and mainly genetically determined. The true natural role of transovarial transmission is not yet well understood. Thus, the breaking up and/or prevention of epidemics would be possible only with a thorough knowledge of the relation between the above biological factors and the epidemiological situation. A list is provided of the naturally or experimentally Aedes aegypti transmitted arboviruses (103), protozoans (5) and filaria (20).
Assuntos
Aedes/fisiologia , Infecções por Arbovirus/transmissão , Dengue/transmissão , Insetos Vetores , Aedes/microbiologia , Animais , Arbovírus/fisiologia , Brasil , Vírus da Dengue/fisiologia , Ecologia , Feminino , Humanos , Masculino , Febre Amarela/transmissãoRESUMO
Two new rhabdoviruses, designated Carajas and Maraba, are described. Both were isolated from phlebotomine sand flies (Lutzomyia spp.) collected in the Amazon basin of Brazil. One recovery of Carajas virus was made from male sand flies. By complement-fixation and neutralization tests both agents were shown to be members of the vesicular stomatitis virus (VSV) serogroup (genus Vesiculovirus). The pathogenicity of the two viruses in mice and Vero cells is similar to that of VSV-Indiana and VSV-New Jersey. Both Carajas and Maraba viruses replicated in Lutzomyia longipalpis following intrathoracic inoculation, and both agents were transovarially transmitted in this sand fly species.