Baudon_2026_Stage-specific impact of key vector competence drivers on Rift valley fever virus dynamics in Aedes and Culex mosquitoes

Rift Valley Fever Virus (RVFV) is an arbovirus responsible for significant mortality and morbidity in both humans and animals. Classified by the WHO as a priority pathogen, RVFV is at risk of worldwide emergence notably due to a large vector species spectrum. As other arboviruses, RVFV vector competence (VC) is driven by genetic and environmental factors. Understand how these factors shape RVFV transmission by mosquitoes is therefore critical to mitigate Rift Valley fever emergence and spread. Conversely to dengue, chikungunya or Zika viruses, little is known on the impact of major VC drivers such as mosquitoes species or virus dose for RVFV. In addition, some potential VC drivers have been overlooked for most arboviruses, such as the cellular origin of viruses used in VC assays. Finally, intra-vector infection dynamics (DIV), represented by the distribution of extrinsic incubation period (EIP) within the mosquito population, remains a black box for many vector-arbovirus pairs. Here, we solved some of these gaps by feeding Aedes aegypti and Culex quinquefasciatus mosquitoes with the RVFV ZH548 reference strain prior to detect, at various time post RVFV exposure, infectious virus in mosquito tissues representative of infection, dissemination and transmission stages. These data were then used to model RVFV DIV for both mosquito species. Major VC variations were observed according to mosquito species, virus dose and cell line used for virus stock production, in a stage-specific manner. Furthermore, key differences were unveiled between the DIV of Ae. aegypti and Cx. quinquefasciatus mosquitoes. This study highlights the pattern of RVFV dynamics in mosquitoes according to major VC drivers, and provides a reference data set upon standardized experimental VC assay in two major RVFV vector genera (Aedes and Culex). Altogether, this work opens new avenues towards the understanding RVFV-mosquito interactions, and how they can modulate RVFV emergence and spread.