259 - Using DNA Barcoding and eDNA to Guide Field Treatment Decisions for Aedes aegypti

Accurate identification of Aedes aegypti and Aedes sierrensis is critical for operational mosquito control in California, where these morphologically similar species differ greatly in public-health importance. However, field-collected specimens can be damaged, desiccated, or missing diagnostic features, limiting the usefulness of traditional morphological keys. We developed and validated a DNA barcoding assay targeting the mitochondrial COI gene and implemented it using qPCR to enable rapid, species-level identification from minimal or degraded material. The assay was evaluated using adults, larvae, and eggs of both species and demonstrated high sensitivity and specificity across tissue types. In operational contexts, identifiable DNA was obtained from severely damaged adults, including specimens reduced to a single leg. This enabled confirmation of a non-risk species and prevented unnecessary deployment of personnel and resources.

Furthermore, we explored the use of environmental DNA (eDNA) to detect species’ presence from container water without requiring intact specimens. Water samples from flowerpots, fountains, In2Care traps, and residential containers were filtered and tested using the same assay. eDNA from Ae. aegypti was successfully detected even after larvae were removed or when water had been treated with pyriproxyfen. Field investigations identified mosquito reproduction activity at residential sites and nurseries, enabling targeted responses in the absence of discovered larvae. These findings demonstrate that container water can serve as a molecular record of recent mosquito activity.

Together, DNA barcoding and eDNA analysis have expanded our district’s capacity to confirm species in challenging circumstances. These tools complement, rather than replace, morphology and provide operational confidence when traditional methods fail.