Wutai Mosquito (Phasivirus wutaiense): Identification and Characterization in Rio de Janeiro's Field Mosquitoes

Résumé

Aim: Numerous RNA viruses have recently emerged, posing threats to humans and causing harm to animals and plants. Among these, bunyaviruses stand out as one of the largest RNA virus groups capable of infecting a wide range of hosts, including invertebrates, vertebrates, and plants. In recent years, new insect-specific viruses have been isolated from mosquitoes and phlebotomine sandflies worldwide. However, little is known regarding the impact of these viruses on the vector life cycles and the stages of oviposition, breeding, blood feeding, and the mosquito’s lifespan. This study describes the first detection and characterization of a recently discovered bunyavirus known as the Wutai mosquito phasivirus in South America.Study Design: A prospective study was conducted in Rio de Janeiro to monitor arbovirus presence in mosquitoes.Place and Duration of Study: The fieldwork, 2013-2017, was carried out in the neighborhoods of Rio de Janeiro city, where the Olympic games' sports facilities were set up. In addition, collections were carried out during a dengue outbreak in two municipalities in the north of Rio de Janeiro State in 2015.Methodology: Passive traps were set in 11 health units and seven additional locations. Trapping also occurred in two northern municipalities with high dengue fever incidence. Weekly collections used BG sentinel traps, and captured mosquitoes were analyzed in the laboratory. Mosquitoes were identified to the genus level, and species confirmation was done via molecular analyses. Pools of up to 250 mosquitoes were prepared for molecular analysis. RNA was extracted from mosquito homogenates and analyzed via RT-PCR. The resulting amplicons were sequenced, aligned, and phylogenetic trees were constructed using maximum likelihood methods to understand evolutionary relationships.Results: A total of 1,866 adult mosquitoes were trapped for bunyavirus screening, with 1,465 identified as Culex spp. and 401 as Aedes spp. Blood meal analysis from engorged females revealed human and dog sources. Wutai mosquito phasivirus was confirmed in complex Culex pipiens quinquefasciatus and other Culex species, with one pool of male Aedes aegypti also testing positive. The transmission route and ecological impact remain unknown. Strains in Rio de Janeiro clustered together, but further research is needed to understand the virus's diversity and evolution.Conclusion: This study reports the first detection and characterization of the Wutai mosquito phasivirus in Brazil. It confirms the virus's presence in primary urban vectors, Culex spp. and Aedes spp., with a high prevalence and wide distribution in Rio de Janeiro. These findings enhance our understanding of mosquito-specific virus distribution and contribute to studies on virus evolution and vector competence for transmitting pathogenic viruses.