From Infection to Transmission: Determinants of Arbovirus Vector Competence in Mosquitoes

Abstract

Arthropod-borne viruses (arboviruses), specifically those transmitted by mosquitoes, are an increasing public health threat. This trend is amplified by globalization and climate change, which enable their spread into new regions. However, the transmission dynamics and vector competence of many arboviruses remain poorly understood, with more than 90% of potential virus-mosquito combinations remaining untested. This lack of knowledge limits accurate risk assessment and preparedness. Understanding how key determinants shape the transmission of arboviruses by mosquitoes is therefore of increasing importance. In this dissertation, the transmission dynamics of arboviruses endemic to (West Nile virus, Tahyna virus) and exotic to Europe (Snowshoe hare virus, Oropouche virus, Barmah Forest virus) were assessed, including a comparison of the two major West Nile virus lineages. Across the 29 virus-mosquito combinations tested, infection was observed in 97% of combinations, whereas transmission occurred in only 41%, demonstrating that infection does not necessarily lead to transmission. Vector competence varied substantially across mosquito taxa, with Aedes albopictus exhibiting the broadest transmission profile, and differed between viruses and viral lineages. All three exotic viruses were able to be transmitted by mosquitoes from Europe, highlighting the potential threat of those viruses. Effects of temperature on vector competence were heterogeneous and dependent on the specific virus-mosquito combinations. The minimum infectious dose was lower for West Nile virus lineage 2, compared with lineage 1. Overall, this dissertation demonstrates that vector competence is highly context-dependent and shaped by interactions between mosquito species, virus, temperature, and viral dose. These findings enable a more realistic assessment of arbovirus risk and highlight the need for context-specific evaluations of vector competence, as results cannot be generalized even across closely related mosquitoes or viruses.