West Nile virus is transmitted within mosquito populations through infectious mosquito excreta

Abstract

Understanding transmission routes of arboviruses is key to control their epidemiology and global health burden. Using West Nile virus and Culex mosquitoes, we tested whether arboviruses are transmitted through mosquito excreta. First, we determined the presence of infectious virions in excreta and quantified a high concentration of infectious units per excreta. Second, we showed that virion excretion starts early after oral infection and remains constant for a long period, regardless of mosquito infection level. These results highlight the infectiousness of excreta from infected mosquitoes. Third, we found that both larvae and pupae were susceptible to infection, although pupae were highly permissive. Forth, we established the proof-of-concept that immature mosquitoes can be infected by infectious excreta, demonstrating a new excreta-mediated mode of transmission. Finally, by mathematically modelling excreta-mediated transmission in the field, we demonstrated its potential impact on arbovirus epidemiology. Our study uncovers a new route of transmission for arboviruses, unveiling mechanisms of viral maintenance in mosquito reservoirs and of vector species shift that contribute to zoonotic emergence.

Aedes Mosquito Virome in Southwestern Cameroon: Lack of Core Virome, but a Very Rich and Diverse Virome in Ae. Africanus Compared to Other Aedes Species

“…In addition to arboviruses capable of infecting both vertebrate and invertebrate cells, the mosquito virome (viral part of the microbiota) also contains a large proportion of viruses which can only infect vertebrate cells and are referred to as Insect Specific Viruses (ISVs) [11]. The main mechanism of transmission and maintenance of ISVs is through vertical transmission (from an infected female mosquito to their offspring) [13], although recent research has suggested another 2 potential mechanism for virus transmission, which is through mosquito excreta [12][13][14].. ISVs being transferred from mosquito generation to generation in a particular mosquito population for a period of time are referred to as the "core virome", a clear quantitative definition is currently lacking [15]. Although the exact mechanism of microbial interactions is not fully understood, ISVs such as Phasi Charoen-like virus (PCLV), Palm Creek virus and bacteria such as Wolbachia have been hypothesized to modulate their mosquito host with respect to vector competence for important arboviruses such as West Nile virus (WNV), Dengue Virus (DENV), Zika virus (ZIKV) [16][17][18][19].…”