Influence of biotic factors on Rift Valley Fever virus infection dynamics in 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 its large vector species spectrum. Understanding how genetic and environmental (a)biotic factors shape RVFV transmission by mosquitoes is therefore critical to prevent Rift Valley fever emergence and spread. Studies often focused on main vector competence (VC) drivers such as mosquitoes species or virus dose, for arboviruses currently considered as major human threats worldwide like dengue, chikungunya or Zika viruses. Other potential VC drivers have been overlooked, like the cellular origin of viruses used in VC assays, while some mosquito-borne viruses remain understudied including RVFV. In addition, intra-vector infection dynamics (IVD), represented by the extrinsic incubation period (EIP) distribution 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 reference RVFV ZH548 strain prior to measure viral infection, dissemination and transmission in individual mosquitoes and estimate RVFV IVD. Major VC variations were observed according to mosquito, virus dose and cell line used for virus stock production together with key differences in IVD between Ae. aegypti and Cx . quinquefasciatus . This study provides a reference data set of mosquito VC for RVFV, for a range of host-like virus doses and stocks, including the EIP range for the two major RVFV vector genera ( Aedes and Culex ). Altogether, this work opens new avenues towards the understanding RVFV-mosquito interactions, and how they impact RVFV emergence and spread.