49 - First Detection of Aedes aegypti in Idaho Confirmed by DNA Barcoding

Abstract: On August 11, 2025, the Canyon County Mosquito Abatement District (CCMAD) recorded the first confirmed detection of Aedes aegypti in Idaho. A single adult female was collected from a gravid trap deployed during routine Culex pipiens population and arbovirus surveillance in Nampa, Idaho. Despite damage to key morphological features, CCMAD staff identified the specimen as Ae. aegypti, and the identification was independently verified by external experts with extensive mosquito identification experience. To confirm morphological species identity, three legs from the specimen were submitted to an independent laboratory for DNA extraction, amplification, and sequencing. Amplification of the cytochrome oxidase subunit I (COI) mitochondrial gene produced a sequence with greater than 99% homology to Aedes aegypti in both the Basic Local Alignment Search Tool (BLAST) and Barcode of Life Data System (BOLD) alignments, confirming the morphological identification. The pinned specimen has since been archived at CCMAD and stored at −80 °C as a voucher reference for future verification. Follow-up surveillance was conducted at and around the collection site using five ovicups and six Biogents Sentinel 2 traps (BG traps). Ovicups were deployed for two weeks and while BG traps were deployed once a week for twenty-four hours and baited with dry ice to attract host-seeking mosquitoes. Trapping continued through the end of 2025 mosquito season. No additional Ae. aegypti adults or eggs were collected, suggesting a single introduction event rather than an established population. This detection underscores the importance of integrating morphological and molecular diagnostic approaches for accurate species identification and early detection of invasive vectors. Continued surveillance will be critical to assess potential future introductions and establishment risk as Aedes mosquitoes expand their geographic range across the western United States.