Molecular Detection of Yellow Fever Virus in Haemagogus janthinomys Mosquitoes (Diptera: Culicidae) in a Rural Settlement in the State of Pará, Brazilian Amazon, 2024

Abstract

Yellow fever (YF) is an acute and potentially fatal hemorrhagic disease caused by the Yellow Fever virus (YFV), endemic to sub-Saharan Africa and several tropical countries, including Brazil. In Brazil, the Amazon region is considered the main endemic area. YFV is maintained in a sylvatic cycle involving Neotropical primates and mosquitoes of the genera Haemagogus and Sabethes, acting as primary and secondary vectors, respectively. In March 2024, entomovirological surveillance was conducted in Santa Bárbara do Pará, Pará, Brazil. A total of 286 mosquitoes were collected, classified into 13 species across nine genera, and grouped into 33 pools. Seventeen pools were tested by RT-qPCR for Orthoflavivirus (YFV, DENV, WNV, SLEV), Alphavirus (CHIKV, MAYV), and Orthobunyavirus (OROV). YFV was detected in four Haemagogus janthinomys pools, with Ct values ranging from 22.2 to 27.9. Metagenomic sequencing confirmed the presence of YFV with assigned reads and >99% protein identity. Notably, the detection occurred without human cases or primate deaths, enabling timely vaccination of the local population. These findings confirm YFV circulation in forested areas of the Belém metropolitan region and reaffirm Hg. janthinomys as a key vector. Our study reinforces the relevance of early entomovirological surveillance and preventive strategies, such as vaccination, to mitigate yellow fever reemergence.

Keywords: RT-qPCR; arbovirus; entomovirological investigation; metagenomics.

Figure 1

Location map of the municipality of Santa Bárbara do Pará, highlighting the collection site of the investigated mosquito species. The figure was created using QGIS v.3.22 (https://qgis.org/en/site/, accessed on 6 July 2025) with cartographic data from the Brazilian Institute of Geography and Statistics (IBGE, 2022) (https://www.ibge.gov.br/, accessed on 6 July 2025) and raster layers from the OpenStreetMap project (https://www.openstreetmap.org/, accessed on 6 July 2025) Panel (A) shows the state of Pará; panel (B) shows South America, with Brazil outlined in red and Pará outlined in orange; and panel (C) shows the boundaries of the municipality of Santa Bárbara do Pará, indicating the collection site with a red marker.