Submitted by the MVCAC VVBD Committee
Birhanie, S.K., Hans, J., Castellon, J.T. et al. 2026. Sci Rep (2026). https://doi.org/10.1038/s41598-026-67765-7
Abstract
The establishment of Aedes aegypti in California, coupled with recent detections of locally transmitted dengue, poses an increasing risk of arboviral transmission and highlights the need for effective control strategies. Conventional approaches are often insufficient due to the cryptic and inaccessible breeding habitats of Ae. aegypti, underscoring the need for innovative tools such as the Sterile Insect Technique (SIT). However, SIT effectiveness depends on a complex interplay of biological, ecological, and operational factors, including release frequency, wild-to-sterile (W:S) ratio, and baseline mosquito density. Understanding how SIT performance varies across density gradients is thus critical for optimizing intervention strategies. This study evaluated the density-dependent effects of SIT releases on Ae. aegypti population suppression in southern California. A targeted SIT program was implemented over two years (2024–2025), involving biweekly releases of in-house reared male Ae. aegypti sterilized using a 55 Gy X-ray dose. A total of 31 sites were stratified into high-, medium-, and low-mosquito density groups based on 2023 baseline data and treated with wild-to-sterile (W:S) ratios of 1:100, 1:50, and 1:20. Adult Ae. aegypti populations were monitored weekly using BG-2 Sentinel traps and analyzed using a negative binomial generalized linear mixed model. Our results indicated that SIT implementation resulted in consistent and substantial Ae. aegypti population reductions across all density groups. In high-density areas, abundance declined by 59–78% in 2024 and up to 88% in 2025, while reductions in low-density areas were more modest in 2024 (19–43%) but increased in 2025 (38–71%), both compared to the baseline (2023). Our findings demonstrate that increasing the W:S ratio generally enhanced Ae. aegypti suppression, although the magnitude of the response varied according to baseline mosquito density. These findings provide strong evidence that targeted SIT can achieve substantial and sustained suppression of Ae. aegypti populations, with effectiveness driven by both release intensity and baseline mosquito density. Our results highlight the need for a shift from maximizing to optimizing W: S ratios by identifying context-specific “impact thresholds” that balance suppression efficiency with operational costs.