RESUMO
Aedes albopictus (Skuse) is an Asiatic mosquito species that has spread and colonized all continents except Antarctica. It has major public health importance because it is a potential vector of several pathogens. The objectives of our study were to analyze the vector competence of urban and rural strains of Ae. albopictus from São Paulo State (Brazil) for Venezuelan equine encephalitis virus (VEE) subtypes IC, ID, and IF, and to evaluate the effect of infection with subtype IC of VEE on mosquito longevity. Both mosquito strains were susceptible to subtypes IC and ID, but the infection rate for subtype IF was low. Infection and transmission rates of Ae. albopictus for subtype IC were similar to those reported for Ochlerotatus taeniorhynchus (Wiedemann). The high infection, dissemination, and transmission rates for subtype ID reported for Oc. fulvus (Wiedemann) and Culex (Melanoconion) spp. are comparable with those found in this study. We found significant differences in the susceptibility to subtype IC between rural and urban populations of São Paulo. Significant survival rate differences were observed between uninfected and infected mosquitoes, but there were no differences in survival between rural and urban mosquito strains.
Assuntos
Aedes/virologia , Vírus da Encefalite Equina Venezuelana/isolamento & purificação , Encefalomielite Equina Venezuelana/veterinária , Doenças dos Cavalos/virologia , Insetos Vetores/virologia , Aedes/fisiologia , Animais , Brasil , Encefalomielite Equina Venezuelana/epidemiologia , Encefalomielite Equina Venezuelana/transmissão , Geografia , Doenças dos Cavalos/epidemiologia , Doenças dos Cavalos/transmissão , Cavalos , Insetos Vetores/fisiologia , Saúde da População Rural , Saúde da População Urbana , Venezuela/epidemiologiaRESUMO
Allpahuayo virus was initially isolated from arboreal rice rats (Oecomys bicolor and Oecomys paricola) collected during 1997 at the Allpahuayo Biological Station in northeastern Peru. Serological and genetic studies identified the virus as a new member of the Tacaribe complex of the genus Arenavirus. The small (S) segment of the Allpahuayo virus prototype strain CLHP-2098 (Accession No. AY012686) was sequenced, as well as that of sympatric isolate CLHP-2472 (Accession No. AY012687), from the same rodent species. The S segment was 3382 bases in length and phylogenetic analysis indicated that Allpahuayo is a sister virus to Pichinde in clade A. Two ambisense, nonoverlapping reading frames were identified, which result in two predicted gene products, a glycoprotein precursor (GPC) and a nucleocapsid protein (NP). A predicted stable single hairpin secondary structure was identified in the intergenic region between GPC and NP. Details of the genetic organization of Allpahuayo virus are discussed.
Assuntos
Arenavirus/isolamento & purificação , Sigmodontinae/virologia , Sequência de Aminoácidos , Animais , Arenavirus/genética , Arenavirus/imunologia , Sequência de Bases , Testes de Fixação de Complemento , DNA Intergênico , Genoma Viral , Glicoproteínas/genética , Dados de Sequência Molecular , Nucleocapsídeo/genética , Peru , Filogenia , Sorotipagem , Proteínas do Envelope Viral/genéticaRESUMO
During field studies of enzootic Venezuelan equine encephalitis (VEE) viruses associated with epizootic emergence, a large number of virus isolates were made in sylvatic foci of Venezuela and Colombia. To rapidly characterize these isolates, antigenic subtypes were determined by means of immunofluorescence and by single-strand conformational polymorphism (SSCP) analysis by use of an 856-bp fragment from the P62 gene, which we used to distinguish genetic variants. Representative isolates were sequenced to assess the sensitivity of SSCP to detect genetic differences. The SSCP analysis distinguished isolates differing by as little as 1 nucleotide; overall, differences of > or = 1 nucleotide were recognized 89% of the time, and the sensitivity to distinguish strains that differed by only 1 or 4 nucleotides was 17 and 57%, respectively. Phylogenetic analyses of representative sequences showed that all recent isolates from the Catatumbo region of western Venezuela and the middle Magdalena Valley of Colombia were closely related to epizootic subtype IAB and IC strains; strains from Yaracuy and Miranda States were more distantly related. Cocirculation of the same virus genotype in both Colombian and Venezuelan foci indicated that these viruses are readily transported between enzootic regions separated by > 300 km. The SSCP analysis appears to be a simple, fast, and relatively efficient method of screening VEE virus isolates to identify meaningful genetic variants.