217 - Implementing Sterile Insect Technique in St. Johns County: Program Development from Rearing to Field Release

Abstract: Aedes aegypti a global vector of dengue, chikungunya, and Zika re-emerged in St. Johns County in 2016 after 24 years of absence and has now developed resistance to pyrethroids. To address this, the Anastasia Mosquito Control District (AMCD) established a Sterile Insect Technique (SIT) Program, following the phased conditional approach recommended by the World Health Organization and the International Atomic Energy Agency. Phase 0 was completed in 2023 securing funding, infrastructure, and partnerships. Phase I began in 2024 with baseline field surveillance and a practical larval diet- liver power in cellulose capsules- for scalable mass-rearing. Dosimetry calibration (standard curve R²=0.98 and dosed uniformity rate=1.3) confirmed the reliable dose measurements. The minimum effective X-ray dose required by adult males for ≥99% sterility with minimum fitness cost was 47.13±2.09 Gy and a target dose of 50 Gy yielded a mating competitiveness index of 1.12, showing sterile males were as competitive as wild males under laboratory conditions. These results advanced the program to Phase II with three mark-release-recapture (MRR) trials planned to assess sterile male dispersal, survival, and longevity across seasons. Two trials were completed in summer and fall, with the third trial set for next spring. Successful completion of Phase II will lead to Phase III, scaled-up weekly sterile male releases to evaluate field efficacy, a critical step toward Phase IV- operational deployment as a public health intervention.