Effect of chikungunya, Mayaro and Una virus coinfection on vector competence of Aedes aegypti mosquitoes

The mosquito-borne alphaviruses chikungunya (CHIKV), Mayaro (MAYV) and the lesser known Una (UNAV) are currently co-circulating in Latin America, sharing their geographical and ecological niche with the <i>Aedes aegypti</i> mosquito. The sylvatic MAYV cycle and the unknown cycle of UNAV could possibly spill over and become urban transmission cycles involving <i>Ae. aegypti</i>. Despite their potential impact on public health, we know little about arboviral coinfections in humans, animals or mosquitoes. Especially the effect of coinfections on transmission by <i>Ae. aegypti</i> mosquitoes is understudied. We investigated the vector competence of <i>Ae. aegypti</i> for single, dual, and triple exposures with UNAV, MAYV and CHIKV, provided simultaneously in an infectious blood meal. Mosquitoes were incubated for ten days at 28 °C and 70 % humidity. After RNA extractions from mosquito bodies and saliva, the presence and relative quantity of each virus in coinfected mosquitoes was determined. We show that <i>Ae. aegypti</i> can become infected with all three viruses simultaneously, and transmit at least two alphaviruses in a single mosquito bite after dual or triple infection. Additionally, we show for the first time that <i>Ae. aegypti</i> is a competent vector for UNAV, and that dual infections do not influence vector competence. In triple coinfections, however, the total viral load carried by mosquitoes decreases, lowering the transmission potential. Understanding how coinfections affect arbovirus biology and transmission of is essential for assessing public health risks. However, emerging <i>Ae. aegypti</i>-vectored arboviruses and coinfections are a One Health concern, as ecological and environmental changes will increasingly drive the geographic distributions of viruses, vectors, and hosts in the future.