RESUMO
Vertical transmission to progeny ensures the maintenance of arboviruses in their natural vectors. This mechanism is largely reported for dengue virus (DENV) and yellow fever virus (YFV). Few studies have addressed this mechanism for Zika virus (ZIKV), Mayaro virus (MAYV) and other arboviruses. The present study investigated the natural infection rate by arboviruses in 4490 Aedes (Stegomyia) aegypti and 296 Aedes (Stegomyia) albopictus (Diptera: Culicidae) reared from eggs collected with ovitraps in Cuiabá, Mato Grosso State, from February to July, 2017. After viral RNA extraction and reverse transcriptase-polymerase chain reaction protocols for 10 flaviviruses and five alphaviruses, nucleotide sequencing and three passages in C6/36 cells, eight pools of Ae. aegypti positive for DENV-4 genotype II, seven for ZIKV Asian genotype and two for MAYV genotype L were found. In addition, two Ae. albopictus pools were positive for DENV-4 genotype II and two were positive for ZIKV Asian genotype. Infection was confirmed by viral isolation in all positive pools for DENV-4 and for MAYV and in eight of nine for ZIKV. This mechanism may contribute to the spread of arboviruses during epidemics and also to their maintenance in natural vectors during interepidemic periods.
Assuntos
Aedes/virologia , Alphavirus/fisiologia , Vírus da Dengue/fisiologia , Mosquitos Vetores/virologia , Zika virus/fisiologia , Animais , Brasil , Feminino , MasculinoRESUMO
To assess the clinical relevance of a semi-quantitative measurement of human cytomegalovirus (HCMV) DNA in renal transplant recipients within the typical clinical context of a developing country where virtually 100 per cent of both receptors and donors are seropositive for this virus, we have undertaken HCMV DNA quantification using a simple, semi-quantitative, limiting dilution polymerase chain reaction (PCR). We evaluated this assay prospectively in 52 renal transplant patients from whom a total of 495 serial blood samples were collected. The samples scored HCMV positive by qualitative PCR had the levels of HCMV DNA determined by end-point dilution-PCR. All patients were HCMV DNA positive during the monitoring period and a diagnosis of symptomatic infection was made for 4 of 52 patients. In symptomatic patients the geometric mean of the highest level of HCMV DNAemia was 152,000 copies per 106 leukocytes, while for the asymptomatic group this value was 12,050. Symptomatic patients showed high, protracted HCMV DNA levels, whereas asymptomatic patients demonstrated intermittent low or moderate levels. Using a cut-off value of 100,000 copies per 106 leukocytes, the limiting dilution assay had sensitivity of 100 per cent, specificity of 92 per cent, a positive predictive value of 43 per cent and a negative predictive value of 100 per cent for HCMV disease. In this patient group, there was universal HCMV infection but relatively infrequent symptomatic HCMV disease. The two patient groups were readily distinguished by monitoring with the limiting dilution assay, an extremely simple technology immediately applicable in any clinical laboratory with PCR capability.