Estudo clínico-epidemiológico e laboratorial das arboviroses e associação com índices vetoriais em áreas endêmicas do estado do Maranhão, Brasil

Abstract

The main arboviral diseases registered in Brazil are dengue, chikungunya and zika, transmitted by the Aedes aegypti mosquito. They have similar symptoms, which makes accurate clinical diagnosis difficult. The objective was to conduct a clinical-epidemiological and laboratory study of arboviruses using molecular biology techniques and to associate the epidemiological aspects of arboviruses with vector indices of Aedes aegypti from endemic areas of Maranhão. Venous blood samples were collected from individuals with suspected arboviruses in the municipalities of Caxias, Codó, Peritoró, and São Mateus do Maranhão from January to July 2019 (Caxias) and from February to June 2022. Samples were subjected to RNA extraction and then tested by RT-qPCR to investigate infection by dengue (DENV-1 to 4), Zika (ZIKV), and Chikungunya (CHIKV) viruses. Positive samples were inoculated into cell culture to isolate the virus and increase the viral load for subsequent nucleotide sequencing. A total of 171 human samples were analyzed, of which 72 were positive, 68 (39.7%) from Caxias; two (2) (1.1%) from Codó; one (1) (0.6%) from Peritoró; and one (1) (0.6%) from São Mateus. A total of 58 positive samples (85.3%) corresponded to infections caused by DENV-1, 4 (5.9%) by DENV-2, one (1) (1.5%) by DENV-3 and in 6 (7.3%) samples, the presence of CHIKV was detected, being a co-infection caused by DENV-1 and CHIKV observed in Caxias. DENV-1 genotype V was detected in four samples analyzed and CHIKV ECSA genotype was detected in one sample. The largest number of human positive samples collected was obtained in Caxias, where DENV-1, DENV-2, DENV-3 and CHIKV were detected, confirming the circulation of these viruses in the interior of Maranhão. The characterization of positive patients showed that males, brown skin, aged 5 to 9 years, and residents of urban areas were the most affected by arboviruses. Fever was the most frequent symptom in both sexes, followed by headache in men and myalgia and nausea in women. The highest number of positive cases in Caxias was observed in Vila Paraíso, followed by Nova Caxias and Seriema peripheral neighborhoods of the city. DENV-3 was detected in the Vila São José neighborhood (Caxias-MA). There was a positive effect of LIRAa on the incidence of dengue (r2 = 0.0352; p = 0.0062) in Maranhão. All municipalities in the state that in any cycle of 2022 presented infestation rates of Ae. aegypti in a situation of alert or high risk, also exhibited high incidences of dengue or chikungunya. The research highlights the importance of carrying out more virological, entomological and epidemiological monitoring studies that provide an overview of the situation of arboviruses in areas where they are endemic and favor the development of effective preventive measures that effectively collaborate with the control and reduction of outbreaks and epidemics of these diseases.