Surveillance of Aedes aegypti and Aedes albopictus in the State of Illinois

Mosquito communities were actively sampled using a variety of traps in 8 counties in south-eastern Illinois with the intent to detect whether Aedes albopictus and Ae. aegypti were present in these locations. Specimens collected through routine surveillance and shared by 8 local public health departments or mosquito abatement districts were also identified to species to detect the presence of this species across a wider range of counties. While Ae. albopictus was found to be present in all of the 8 counties actively sampled (providing the first records of occurrence for these locations) and for 6 of the counties for which we received collections, the numbers of Ae. albopictus collected differed among locations. Culex spp. mosquitoes were also caught in the traps. Aedes aegypti was not found to be present in these locations. All collected Aedes and Culex spp. were screened for 6 arboviruses, though no positives were found. By sequencing a segment of the mitochondrial CO1 gene of a subset of female Ae. albopictus from 10 locations in Illinois we identified 17 unique genetic sequences (haplotypes), with likely at least 4 distinct genetic lineages being present in Illinois, with different geographic areas having distinct genetic populations. This suggests that the composition of this vector species in Illinois is the result of a complex and dynamic invasion history. Major questions for future work are how these genetic differences relate to the increase in abundance of Ae. albopictus in recent years, and whether there are phenotypic differences among these populations that might impact the epidemiology of vector-borne diseases in Illinois.