Population mobility, demographic, and environmental characteristics of dengue fever epidemics in a major city in Southeastern Brazil, 2007-2015

Potential breeding containers of Aedes aegypti (Linnaeus, 1762) and Aedes albopictus (Skuse, 1894) at strategic points in a city in the eastern region of Maranhão

Potential breeding containers for Aedes aegypti and Aedes albopictus mosquitoes are found in different environments, these places are considered by the National Dengue Control Program in Brazil as strategic points (SP), which have favorable conditions for the development of those insects. The aim of this study is to identify potential breeding containers for A. aegypti and A. albopictus at strategic points in the city of Codó, Maranhão. This study was conducted in five districts, one in each administrative area of the city. A survey of the types and quantity of existing strategic points in each neighborhood was carried out, and surveys of these properties were carried out to inspect the potential breeding containers, with the collection of the vectors' number of immatures found at them. 125 properties were inspected of which 76.91% and 81.25% were vacant lots in the dry and rainy seasons, respectively. There was a difference between the median of the different strategic points (H = 21.96; p < 0.0001), For A. aegypti, there was no difference between the medians of number of immatures regarding the strategic points (H = 3.71; p = 0.28). The total number of immature A. albopictus was higher in vacant lots than in workshops (H = 9.41; p = 0.02, p < 0.05). 4,356 and 4,911 potential breeding containers were found in the dry and rainy seasons, respectively. Regarding the potential breeding containers, 7 (0.16%) and 47 (0.96%) were found with immature vectors, in the dry and rainy seasons, respectively. There were more positive containers in the rainy season for which there was a difference between the median of the number of mosquitoes per positive container (H = 15.66; p = 0.01), the number of immatures for the tires group was greater than Vases and Fixed groups (p < 0.05); the same result was observed in the analyses of the species in the separate form. The impressive number of potential breeding containers found in the SP in both seasons highlights the importance of developing control strategies for these vectors, with emphasis on places such as vacant lots, workshops, tire shops and junkyards, which are serving as dispersal urban sites of vectors.

Identification of risk areas for arboviruses transmitted by Aedes aegypti in northern Brazil: A One Health analysis

Introduction

The complex and growing problem generated by the rapid expansion of unplanned urban areas includes high population density and increased infestation by vectors responsible for the transmission of several diseases. This requires interdisciplinary and intersectoral interventions due to the burden of diseases, especially those caused by arboviruses, which can present severe forms and generate significant pressure on health systems, especially in more vulnerable regions. The objective of this study was to analyze the spatial distribution of arboviruses transmitted by Aedes aegypti (dengue, Zika, and chikungunya) and assess their correlations with demographic, social, and environmental data from the state of Tocantins, Brazil.

Methods

This was an ecological time series study of the dengue, Zika, and chikungunya arboviruses in the state of Tocantins. Local Moran's indices were used to observe the spatial autocorrelation of cases and to delimit clusters of high and low risks, correlating them with socioenvironmental indicators, in addition to analyses to detect case clusters.

Results

The state reported a mean incidence of 591 annual cases of arbovirus infections per 100,000 inhabitants and a stationary trend with seasonal pattern. Female Pardo individuals aged 20-39 years, with an education level of below college education, were the most affected; Palmas and Araguaína, the two largest cities in the state in terms of economy and population, were the most affected.

Conclusion

A better understanding of the interaction between social characteristics, the environment, and ecology of wild animals and vectors is important for the development of mechanisms to predict outbreaks as well as to develop strategies to reduce and/or mitigate recurring arboviral epidemics and other diseases.

How heterogeneous is the dengue transmission profile in Brazil? A study in six Brazilian states

Dengue is a vector-borne disease present in most tropical countries, infecting an average of 50 to 100 million people per year. Socioeconomic, demographic, and environmental factors directly influence the transmission cycle of the dengue virus (DENV). In Brazil, these factors vary between regions producing different profiles of dengue transmission and challenging the epidemiological surveillance of the disease. In this article, we aimed at classifying the profiles of dengue transmission in 1,823 Brazilian municipalities, covering different climates, from 2010 to 2019. Time series data of dengue cases were obtained from six states: Ceará and Maranhão in the semiarid Northeast, Minas Gerais in the countryside, Espírito Santo and Rio de Janeiro in the tropical Atlantic coast, and Paraná in the subtropical region. To describe the time series, we proposed a set of epi-features of the magnitude and duration of the dengue epidemic cycles, totaling 13 indicators. Using these epi-features as inputs, a multivariate cluster algorithm was employed to classify the municipalities according to their dengue transmission profile. Municipalities were classified into four distinct dengue transmission profiles: persistent transmission (7.8%), epidemic (21.3%), episodic/epidemic (43.2%), and episodic transmission (27.6%). Different profiles were associated with the municipality’s population size and climate. Municipalities with higher incidence and larger populations tended to be classified as persistent transmission, suggesting the existence of critical community size. This association, however, varies depending on the state, indicating the importance of other factors. The proposed classification is useful for developing more specific and precise surveillance protocols for regions with different dengue transmission profiles, as well as more precise public policies for dengue prevention.

Dengue is one of the fastest-growing vector-borne diseases in the world. Currently, vaccines are experimental and are not very effective, so prevention depends on the control of the mosquito Aedes aegypti. Health promotion campaigns aimed at encouraging people to reduce mosquito breeding sites have limited effect. In addition, the heterogeneity of the territories that have dengue becomes a major challenge for the epidemiological surveillance of the disease. Brazil has a territory of continental size, and single standardized surveillance is not very effective for monitoring this arbovirus. Classifying types of dengue dynamics based on features of the epidemiological cycle in each location has the potential to increase the precision of surveillance and control strategies. In our study, we were able to classify areas according to different dengue transmission profiles, ranging from episodic to persistent transmission. These results can provide tools to guide actions aimed at achieving the World Health Organization’s goals of eliminating neglected tropical diseases in countries that have the virus.

[Dengue virus E protein-based luciferase immunosorbent assay for detecting dengue virus IgG antibody]

OBJECTIVE

To establish a luciferase immunosorbent assay (DENV-LISA) based on dengue virus (DENV) E protein, a specific antigen of DENV, for detection of DENV IgG antibody.

METHODS

The fused expression plasmids of DENV1-E1 and DENV2-E2 with luciferase were constructed. The plasmids were transfected into 293T cells, and the fusion protein containing the specific antigen and luciferase was obtained for establishing DENV-LISA. The specificity and sensitivity of DENV-LISA were assessed and compared with those of commercial DENV IgG antibody detection kit (ELISA).

RESULTS

The established DENV-LISA had a positive detection rate of 32.4% and a specificity of 96.6%, showing a similar positive detection rate with the commercial ELISA kit (35.3%; P>0.05). DENV-LISA was capable of detecting positive samples with a 1: 6400 dilution with a high sensitivity. The test values of DENV-LISA did not differ significantly between plates or within plates in the same batch (P> 0.05), suggesting a good reproducibility of the test.

CONCLUSION

The luciferase immunosorbent assay based on DENV E protein has high specificity and sensitivity for detecting DENV IgG antibody, and can be used for early screening, surveillance and epidemiological investigation of DENV infection.