Dados do Trabalho

Título

Molecular characterization of Alphavirus from field-collected mosquitoes in the Northwest of São Paulo State, Brazil.

Introdução

Brazil is considered an epicenter for emerging and re-emerging arboviruses, which significantly affect the public health of many municipalities. São José do Rio Preto (SJRP), located in the Northwest of São Paulo state, is considered an hyperendemic city for arbovirus, due to recurrent dengue epidemics. However, from late 2023 the city exhibited a more worrying scenario marked by the circulation of three serotypes of dengue virus, along with high incidence of CHIKV cases.

Objetivo (s)

Here, we aimed to investigate and molecularly characterize the CHIKV obtained from field-collected mosquitos, to better understand the factors that led to its enhanced transmission rates from 2023.

Material e Métodos

Adult culicids, collected monthly, in six different neighborhoods of SJRP were used for RNA extractions and RT-qPCR to investigate the presence of CHIKV. Positive samples were submitted to whole-genome sequencing. After the quality check and trimming the reads were de novo assembled, and the genomes used in phylogenetic analyses.

Resultados e Conclusão

A total of 676 mosquitoes were collected from October 2023 to April 2024. After molecular testing, 41 samples were diagnosed as positive for CHIKV, corresponding to an incidence rate of 6%. Considering the different species tested, 6% of Ae. aegypti, 9% of Ae. albopictus and 5% of the Culex sp. collected tested positive for CHIKV. We sequenced 32 samples that presented cycle threshold values ranging from 29.3 to 37.9. Genome coverage ranged from 70 to 90% and our phylogenetic analysis showed that all the CHIKV genomes obtained in this study were classified as East/Central/South African (ECSA) lineage. The sequences were clustered in a well-supported monophyletic group together with sequences obtained from infected patients, from SJRP, evidencing a well-established local transmission. Moreover, our sequences were grouped within clades formed mostly by sequences from the Southeast region, from São Paulo and Minas Gerais states, as well as the North region, from Tocantins state, all of them collected in 2023 and 2024, suggesting a recent introduction of these lineage in SJRP. Our findings reinforce the importance of continued genomic surveillance strategies to monitor and prevent new arbovirus epidemics, drived by the emergence of new variants and/or the introduction of new lineages in the region. Moreover, our results highlight the need of implementing more effective vector control measures to reduce the impact of these arboviruses on public health.

Palavras Chave

Chikungunya virus; genomic surveillance; vector control.