Primary Submission Category: Applications in Health and Biology
Causal Evaluation of Larvicide Intervention on West Nile Virus Vectors
Authors: Jian Yang, Trevor Harris, Chan Park, Kristina Lopez, Rebecca Smith,
Presenting Author: Jian Yang*
Effective larval control is a cornerstone of Integrated Vector Management for West Nile virus mitigation. In 2021, the North Shore Mosquito Abatement District in the Chicago area implemented a strategic switch in larvicide products. Evaluating the causal impact of such operational interventions is challenging due to strong seasonality and meteorological confounders (e.g., temperature, precipitation). This study applies quasi-experimental frameworks—specifically Difference-in-Differences and Synthetic Control—to estimate the intervention’s causal effect on Culex mosquito abundance and the West Nile Virus Vector Index using weekly surveillance data (2017–2023). While preliminary Interrupted Time Series models suggested an 11.6% reduction in abundance, they rely solely on temporal controls. To improve identification, we leverage data from neighboring districts as control units. We implement Difference-in-Difference and Synthetic Control methods to construct a data-driven counterfactual that minimizes pre-intervention trend divergence. This research demonstrates the utility of causal inference methods in validating public health interventions where randomized control trials are infeasible, offering robust evidence of larvicide efficacy while addressing complex environmental noise.