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Dengue virus (DENV) 1-4 is the etiological agent of dengue, the most important viral infection transmitted by Aedes spp mosquitoes to humans. Our goal was to identify the circulating DENV in Aedes aegypti collected in an area of Brazil where all four DENV serotypes had already been detected in humans, understand the epidemiology better, and to test the vector as a virological surveillance tool. Twenty-eight larvae pools and 174 females of Aedes aegypti were screened by reverse transcriptase quantitative polymerase chain reaction and semi-nested PCR assays. PCR products were sequenced, and phylogenetic analyses were performed. Nine larvae pools (32.1%) were positive for DENV, four (44.4%) with DENV-3, and five (55.6%) with more than one serotype. Fifteen females (8.6%) were positive for any DENV serotype. DENV-1 isolates belong to genotype V, DENV-2 to American-Asian genotype, DENV-3 to genotypes I and III, and DENV-4 to genotypes I and II. We demonstrate for the first time the co-circulation of all four DENV serotypes in larvae pools and adult Aedes aegypti in a hyperendemic area. This scenario represents a challenge for disease control and reinforces the importance of virological surveillance in the vector as a tool for predicting circulating DENV serotypes in humans.

Background Dengue is a vector-borne disease caused by the dengue virus (DENV). Despite the crucial role of Aedes mosquitoes in DENV transmission, pure vector indices poorly correlate with human infections. Therefore there is great need for a better understanding of the spatial and temporal scales of DENV transmission between mosquitoes and humans. Here, we have systematically monitored the circulation of DENV in individual Aedes spp. mosquitoes and human patients from Caratinga, a dengue endemic city in the state of Minas Gerais, in Southeast Brazil. From these data, we have developed a novel stochastic point process pattern algorithm to identify the spatial and temporal association between DENV infected mosquitoes and human patients. Methods The algorithm comprises of: (i) parameterization of the variogram for the incidence of each DENV serotype in mosquitoes; (ii) identification of the spatial and temporal ranges and variances of DENV incidence in mosquitoes in the proximity of humans infected with dengue; and (iii) analysis of the association between a set of environmental variables and DENV incidence in mosquitoes in the proximity of humans infected with dengue using a spatio-temporal additive, geostatistical linear model. Results DENV serotypes 1 and 3 were the most common virus serotypes detected in both mosquitoes and humans. Using the data on each virus serotype separately, our spatio-temporal analyses indicated that infected humans were located in areas with the highest DENV incidence in mosquitoes, when incidence is calculated within 2.5–3 km and 50 days (credible interval 30–70 days) before onset of symptoms in humans. These measurements are in agreement with expected distances covered by mosquitoes and humans and the time for virus incubation. Finally, DENV incidence in mosquitoes found in the vicinity of infected humans correlated well with the low wind speed, higher air temperature and northerly winds that were more likely to favor vector survival and dispersal in Caratinga. Conclusions We have proposed a new way of modeling bivariate point pattern on the transmission of arthropod-borne pathogens between vector and host when the location of infection in the latter is known. This strategy avoids some of the strong and unrealistic assumptions made by other point-process models. Regarding virus transmission in Caratinga, our model showed a strong and significant association between high DENV incidence in mosquitoes and the onset of symptoms in humans at specific spatial and temporal windows. Together, our results indicate that vector surveillance must be a priority for dengue control. Nevertheless, localized vector control at distances lower than 2.5 km around premises with infected vectors in densely populated areas are not likely to be effective. Electronic supplementary material The online version of this article (10.1186/s13071-018-2662-6) contains supplementary material, which is available to authorized users.

Dengue is currently regarded as a major public health problem worldwide. In a hyperendemic region during an outbreak, we detected the co-circulation of all Dengue virus (DENV) serotypes including two different genotypes of DENV-3 and DENV-4, and concurrent infections with up to three serotypes were identified in symptomatic patients. A total of 49 acute phase plasma samples from patients clinically suspected of dengue were collected during the 4 weeks of May 2013. DENV-1-4 was detected by reverse transcriptase semi-nested polymerase chain reaction in 33 samples (67.3%), of which 26 DNA fragments were sequenced. Twenty samples (76.9%) were identified with a single DENV serotype and six (23.1%) with more than one serotype. DENV-3 was the predominant serotype of the outbreak. On the basis of phylogenetic analyses, DENV-1 isolates belong to genotype V, DENV-2 to American-Asian genotype, DENV-3 to genotypes I and III, and DENV-4 to genotypes I and II.

Dengue virus type 3 genotype I was detected in Brazil during epidemics in 2002-2004. To confirm this finding, we identified this virus genotype in naturally infected field-caught Aedes aegypti mosquitoes and eggs. Results showed usefulness of virus investigations in vectors as a component of active epidemiologic surveillance.

O Dengue virus é o agente etiológico da dengue, a arbovirose mais prevalente no mundo, sendo, anualmente, notificados cerca de 50 milhões de casos. Os mosquitos vetores da dengue pertencem ao gênero Aedes, sendo a espécie Aedes aegypti, o principal vetor. Este trabalho busca o aprimoramento de técnicas de detecção do genoma de Dengue virus em larvas e mosquitos adultos a fim de otimizar os métodos de predição de epidemias que utilizam armadilhas para captura do vetor. Neste trabalho, a presença do genoma viral em mosquitos e larvas foi analisada por RT-PCR. As larvas e mosquitos adultos processados pertencem a um bairro da regional Noroeste de Belo Horizonte, MG, que apresenta os maiores índices de prevalência de dengue nos últimos anos, em Belo Horizonte (36% do total de casos notificados até 2006). Para a captura de ovos e mosquitos adultos foram utilizados quatro métodos de amostragem: Ovitrampa, BG-Trap®R, MosquiTRAPR e Aspirador de NasciR. Dos insetos coletados, 661 fêmeas, 372 machos e 28808 larvas foram macerados e submetidos à extração de RNA. A presença do genoma viral foi detectada por RT-PCR em 13,2% dos pools de larvas de Ae. Aegypti, em 16,6% dos pools de machos da BG-Trap® e em 20% dos pools de machos do Aspirador de Nasci. Para os pools de fêmeas analisados, foi encontrada a presença do genoma viral numa percentagem de 14,3% para a BG-Trap® e 16,6% para a MosquiTRAP. As técnicas moleculares utilizadas se mostraram eficientes, sendo a presença do genoma viral detectada em até 0,1 PFU. As armadilhas se mostraram eficientes na captura do vetor, sendo a MosquiTRAPR mais eficiente em coletas de fêmeas grávidas, capazes de transmitir o vírus. A metodologia é eficiente e pode ser empregada em programas de monitoramento para controle e prevenção da doença.