Abstract
The Asian tiger mosquito, Aedes albopictus, is an invasive species that spreads diseases like chikungunya and has caused outbreaks worldwide. Studies show that mosquito-associated microbes can affect disease transmission. One of those microbes, the parasite Ascogregarina taiwanensis, is common in native and settled mosquito populations (>3 years after introduction) but rare in recently introduced ones. We found that this parasite slows down the spread of the chikungunya virus within the mosquito and decreases its transmission rate by half. Unparasitized mosquitoes spread the virus more easily, suggesting that changes in mosquito-associated microbes could impact disease outbreaks and public health.